Thread: go for a script! / ex: PostgreSQL vs. MySQL
Heya Guys n Gals, Having been following the thread on "go for a script! / ex: PostgreSQL vs. MySQL". I thought I would throw something together in Perl. My current issue is that I only have access to a RH Linux box and so cannot make it cross-platform on my own :-(. Anyhow please find it attached. It runs fine on my box, it doesnt actually write to postgresql.conf because I didnt want to mess it up, it does however write to postgresql.conf.new for the moment. The diffs seem to be writing correctly. There are a set of parameters at the top which may need to get tweaked for your platform. I can also carry on posting to this list new versions if people want. Clearly this lot is open source, so please feel free to play with it and post patches/new features back either to the list or my email directly. In case you cant see my email address, it is nicky at the domain below. I will also post it on me website and as I develop it further new versions will appear there http://www.chuckie.co.uk/postgresql/pg_autoconfig.pl Is this a useful start? Nick
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----- Original Message ----- From: "Nick Barr" <nicky@chuckie.co.uk> To: <pgsql-performance@postgresql.org> Sent: Friday, October 10, 2003 1:35 PM Subject: go for a script! / ex: PostgreSQL vs. MySQL > I will also post it on me website and as I develop it further new versions > will appear there > > http://www.chuckie.co.uk/postgresql/pg_autoconfig.pl Make that http://www.chuckie.co.uk/postgresql/pg_autoconfig.txt Nick
Nick, > Having been following the thread on "go for a script! / ex: PostgreSQL vs. > MySQL". I thought I would throw something together in Perl. Cool! Would you be willing to work with me so that I can inject some of my knowledge of .conf tuning? -- Josh Berkus Aglio Database Solutions San Francisco
Josh Berkus wrote: >Nick, > > > >>Having been following the thread on "go for a script! / ex: PostgreSQL vs. >>MySQL". I thought I would throw something together in Perl. >> >> > >Cool! Would you be willing to work with me so that I can inject some of my >knowledge of .conf tuning? > > > Sounds good to me. I will carry on working on it but I would definitely need some help, or at least a list of parameters to tweak, and some recomended values based on data about the puter in question. So far: shared_buffers = 1/16th of total memory effective_cache_size = 80% of the supposed kernel cache. I guess we also may be able to offer a simple and advanced mode. Simple mode would work on these recomended values, but kick it into advanced mode and the user can tweak things more finely. This would only be recomended for the Guru's out there of course. This may take a bit more time to do though. As I said in the previous email I have only got access to Linux, so cross-platform help would be good too. I will try to make it as easy to do cross platform stuff as possible of course. Nick
>>>>> "NB" == Nick Barr <nicky@chuckie.co.uk> writes: NB> So far: NB> shared_buffers = 1/16th of total memory NB> effective_cache_size = 80% of the supposed kernel cache. Please take into account the blocksize compiled into PG, too... -- =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Vivek Khera, Ph.D. Khera Communications, Inc. Internet: khera@kciLink.com Rockville, MD +1-240-453-8497 AIM: vivekkhera Y!: vivek_khera http://www.khera.org/~vivek/
Nick, > Sounds good to me. I will carry on working on it but I would definitely > need some help, or at least a list of parameters to tweak, and some > recomended values based on data about the puter in question. > shared_buffers = 1/16th of total memory > effective_cache_size = 80% of the supposed kernel cache. But only if it's a dedicated DB machine. If it's not, all memory values should be cut in half. > I guess we also may be able to offer a simple and advanced mode. Simple > mode would work on these recomended values, but kick it into advanced > mode and the user can tweak things more finely. This would only be > recomended for the Guru's out there of course. This may take a bit more > time to do though. What I would prefer would be an interactive script which would, by asking the user simple questions and system scanning, collect all the information necessary to set: max_connections shared_buffers sort_mem vacuum_mem effective_cache_size random_page_cost max_fsm_pages checkpoint_segments & checkpoint_timeout tcp_ip and on the OS, it should set: shmmax & shmmall and should offer to create a chron job which does appropriate frequency VACUUM ANALYZE. > As I said in the previous email I have only got access to Linux, so > cross-platform help would be good too. I will try to make it as easy to > do cross platform stuff as possible of course. Let's get it working on Linux; then we can rely on the community to port it to other platforms. I myself can work on the ports to Solaris and OS X. -- Josh Berkus Aglio Database Solutions San Francisco
Vivek, > NB> shared_buffers = 1/16th of total memory > NB> effective_cache_size = 80% of the supposed kernel cache. > > Please take into account the blocksize compiled into PG, too... We can;t change the blocksize in a script that only does the .conf file. Or are you suggesting something else? -- Josh Berkus Aglio Database Solutions San Francisco
>>>>> "JB" == Josh Berkus <josh@agliodbs.com> writes: JB> Vivek, NB> shared_buffers = 1/16th of total memory NB> effective_cache_size = 80% of the supposed kernel cache. >> >> Please take into account the blocksize compiled into PG, too... JB> We can;t change the blocksize in a script that only does the .conf JB> file. Or are you suggesting something else? when you compute optimal shared buffers and effective cache size, these are in terms of blocksize. so if I have 16k block size, you can't compute based on default 8k blocksize. at worst, it would have to be a parameter you pass to the tuning script.
Vivek, > when you compute optimal shared buffers and effective cache size, > these are in terms of blocksize. so if I have 16k block size, you > can't compute based on default 8k blocksize. at worst, it would have > to be a parameter you pass to the tuning script. Oh, yes! Thank you. -- -Josh Berkus Aglio Database Solutions San Francisco
> NB> So far: > > NB> shared_buffers = 1/16th of total memory > NB> effective_cache_size = 80% of the supposed kernel cache. > > Please take into account the blocksize compiled into PG, too... Would anyone object to a patch that exports the blocksize via a readonly GUC? Too many tunables are page dependant, which is infuriating when copying configs from DB to DB. I wish pgsql had some notion of percentages for values that end with a '%'. -sc -- Sean Chittenden
Sean Chittenden wrote: > > NB> So far: > > > > NB> shared_buffers = 1/16th of total memory > > NB> effective_cache_size = 80% of the supposed kernel cache. > > > > Please take into account the blocksize compiled into PG, too... > > Would anyone object to a patch that exports the blocksize via a > readonly GUC? Too many tunables are page dependant, which is > infuriating when copying configs from DB to DB. I wish pgsql had some > notion of percentages for values that end with a '%'. -sc Makes sense to me --- we already have some read-only GUC variables. -- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania 19073
On Fri, 2003-10-10 at 18:59, Sean Chittenden wrote:
> > NB> So far:
> >
> > NB> shared_buffers = 1/16th of total memory
> > NB> effective_cache_size = 80% of the supposed kernel cache.
> >
> > Please take into account the blocksize compiled into PG, too...
>
> Would anyone object to a patch that exports the blocksize via a
> readonly GUC? Too many tunables are page dependant, which is
> infuriating when copying configs from DB to DB. I wish pgsql had some
> notion of percentages for values that end with a '%'.
Rather than showing the block size, how about we change the tunables to
be physical sizes rather than block based?
effective_cache_size = 1.5GB
shared_buffers = 25MB
Percentages would be slick as well, but doing the above should fix most
of the issue -- and be friendlier to read.
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> NB> shared_buffers = 1/16th of total memory > NB> effective_cache_size = 80% of the supposed kernel cache. I think Sean(?) mentioned this one for FreeBSD (Bash code): echo "effective_cache_size = $((`sysctl -n vfs.hibufspace` / 8192))" I've used it for my dedicated servers. Is this calculation correct? Chris
> >NB> shared_buffers = 1/16th of total memory > >NB> effective_cache_size = 80% of the supposed kernel cache. > > I think Sean(?) mentioned this one for FreeBSD (Bash code): sh, not bash. :) > echo "effective_cache_size = $((`sysctl -n vfs.hibufspace` / 8192))" > > I've used it for my dedicated servers. Is this calculation correct? Yes, or it's real close at least. vfs.hibufspace is the amount of kernel space that's used for caching IO operations (minus the necessary space taken for the kernel). If you're real paranoid, you could do some kernel profiling and figure out how much of the cache is actually disk IO and multiply the above by some percentage, say 80%? I haven't found it necessary to do so yet. Since hibufspace is all IO and caching any net activity is kinda pointless and I assume that 100% of it is used for a disk cache and don't use a multiplier. The 8192, however, is the size of a PG page, so, if you tweak PG's page size, you have to change this constant (*grumbles*). -sc -- Sean Chittenden
In article <1065837333.12875.1.camel@jester>, Rod Taylor <rbt@rbt.ca> writes: >> Would anyone object to a patch that exports the blocksize via a >> readonly GUC? Too many tunables are page dependant, which is >> infuriating when copying configs from DB to DB. I wish pgsql had some >> notion of percentages for values that end with a '%'. > Rather than showing the block size, how about we change the tunables to > be physical sizes rather than block based? > effective_cache_size = 1.5GB > shared_buffers = 25MB Amen! Being forced to set config values in some obscure units rather than bytes is an ugly braindamage which should be easy to fix.
On Sat, 2003-10-11 at 05:22, Harald Fuchs wrote: > In article <1065837333.12875.1.camel@jester>, > Rod Taylor <rbt@rbt.ca> writes: > > >> Would anyone object to a patch that exports the blocksize via a > >> readonly GUC? Too many tunables are page dependant, which is > >> infuriating when copying configs from DB to DB. I wish pgsql had some > >> notion of percentages for values that end with a '%'. > > > Rather than showing the block size, how about we change the tunables to > > be physical sizes rather than block based? > > > effective_cache_size = 1.5GB > > shared_buffers = 25MB > > Amen! Being forced to set config values in some obscure units rather > than bytes is an ugly braindamage which should be easy to fix. But it's too user-friendly to do it this way! -- ----------------------------------------------------------------- Ron Johnson, Jr. ron.l.johnson@cox.net Jefferson, LA USA When Swedes start committing terrorism, I'll become suspicious of Scandanavians.
Josh Berkus wrote:
>>shared_buffers = 1/16th of total memory
>>effective_cache_size = 80% of the supposed kernel cache.
>>
>>
>But only if it's a dedicated DB machine. If it's not, all memory values
>should be cut in half.
>
>
>
>What I would prefer would be an interactive script which would, by asking the
>user simple questions and system scanning, collect all the information
>necessary to set:
>
>max_connections
>shared_buffers
>sort_mem
>vacuum_mem
>effective_cache_size
>random_page_cost
>max_fsm_pages
>checkpoint_segments & checkpoint_timeout
>tcp_ip
>
>and on the OS, it should set:
>shmmax & shmmall
>and should offer to create a chron job which does appropriate frequency VACUUM
>ANALYZE.
>
>
I reckon do a system scan first, and parse the current PostgreSQL conf
file to figure out what the settings are. Also back it up with a date
and time appended to the end to make sure there is a backup before
overwriting the real conf file. Then a bunch of questions. What sort of
questions would need to be asked and which parameters would these
questions affect? So far, and from my limited understanding of the .conf
file, I reckon there should be the following
Here is your config of your hardware as detected. Is this correct ?
This could potentially be several questions, i.e. one for proc, mem,
os, hdd etc
Would affect shared_buffers, sort_mem, effective_cache_size,
random_page_cost
How was PostgreSQL compiled?
This would be parameters such as the block size and a few other
compile time parameters. If we can get to some of these read-only
parameters than that would make this step easier, certainly for the new
recruits amongst us.
Is PostgreSQL the only thing being run on this computer?
Then my previous assumptions about shared_buffers and
effective_cache_size would be true.
If shmmax and shmmall are too small, then:
PostgreSQL requires some more shared memory to cache some tables, x Mb,
do you want to increase your OS kernel parameters?
Tweak shmmax and shmmall
How are the clients going to connect?
i.e. TCP or Unix sockets
How many clients can connect to this database at once?
Affects max_connections
How many databases and how many tables in each database are going to be
present?
Affects max_fsm_pages, checkpoint_segments, checkpoint_timeout
Do you want to vacuum you database regularly?
Initial question for cron job
It is recomended that you vacuum analyze every night, do you want to do
this?
It is also recomended that you vacuum full every month, do you want to
do this?
Thoughts?
Nick
> If shmmax and shmmall are too small, then: > > PostgreSQL requires some more shared memory to cache some tables, x Mb, > do you want to increase your OS kernel parameters? > > Tweak shmmax and shmmall Note that this still requires a kernel recompile on FreeBSD :( Chris
Nick,
> I reckon do a system scan first, and parse the current PostgreSQL conf
> file to figure out what the settings are. Also back it up with a date
> and time appended to the end to make sure there is a backup before
> overwriting the real conf file. Then a bunch of questions. What sort of
> questions would need to be asked and which parameters would these
> questions affect? So far, and from my limited understanding of the .conf
> file, I reckon there should be the following
Hmmm ... but I do think that there should be a file to store the user's
previous answers. That way, the script can easily be re-run to fix config
issues.
> Here is your config of your hardware as detected. Is this correct ?
>
> This could potentially be several questions, i.e. one for proc, mem,
> os, hdd etc
> Would affect shared_buffers, sort_mem, effective_cache_size,
> random_page_cost
Actually, I think this would break down into:
-- Are Proc & Mem correct? If not, type in correct values
-- Is OS correct? If not, select from list
-- Your HDD: is it:
1) IDE
2) Fast multi-disk SCSI or low-end RAID
3) Medium-to-high-end RAID
Other things, we don't care about.
> How was PostgreSQL compiled?
>
> This would be parameters such as the block size and a few other
> compile time parameters. If we can get to some of these read-only
> parameters than that would make this step easier, certainly for the new
> recruits amongst us.
Actually, from my perspective, we shouldn't bother with this; if an admin
knows enough to set an alternate blaock size for PG, then they know enough to
tweak the Conf file by hand. I think we should just issue a warning that
this script:
1) does not work for anyone who is using non-default block sizes,
2) may not work well for anyone using unusual locales, optimization flags, or
other non-default compile options except for language interfaces.
3) cannot produce good settings for embedded systems;
4) will not work well for systems which are extremely low on disk space,
memory, or other resouces.
Basically, the script only really needs to work for the people who are
installing PostgreSQL with the default options or from RPM on regular server
or workstation machines with plenty of disk space for normal database
purposes. People who have more complicated setups can read the darned
documentation and tune the conf file by hand.
> Is PostgreSQL the only thing being run on this computer?
First, becuase it affects a couple of other variables:
What kind of database server are you expecting to run?
A) Web Server (many small fast queries from many users, and not much update
activity)
B) Online Transaction Processing (OLTP) database (many small updates
constantly from many users; think "accounting application").
C) Online Analytical Reporting (OLAP) database (a few large and complicated
read-only queries aggregating large quantites of data for display)
D) Data Transformation tool (loading large amounts of data to process,
transform, and output to other software)
E) Mixed-Use Database Server (a little of all of the above)
F) Workstation (installing this database on a user machine which also has a
desktop, does word processing, etc.)
If the user answers anything but (F), then we ask:
Will you be running any other signficant software on this server, such as a
web server, a Java runtime engine, or a reporting application? (yes|no)
If yes, then:
How much memory do you expect this other software, in total, to regularly use
while PostgreSQL is in use? (# in MB; should offer default of 50% of the RAM
scanned).
> How are the clients going to connect?
>
> i.e. TCP or Unix sockets
We should warn them that they will still need to configure pg_hba.conf.
> How many clients can connect to this database at once?
>
> Affects max_connections
Should add a parenthetical comment that for applications which use pooled
connections, or intermittent connection, such as Web applications, the number
of concurrent connections is often much lower than the number of concurrent
users.
> How many databases and how many tables in each database are going to be
> present?
>
> Affects max_fsm_pages, checkpoint_segments, checkpoint_timeout
Also need to ask if they have an idea of the total size of all databases, in
MB or GB, which has a stronger relationship to those variables.
Also, this will give us a chance to check the free space on the PGDATA
partition, and kick the user out with a warning if there is not at least
2xExpected Size available.
> Do you want to vacuum you database regularly?
>
> Initial question for cron job
>
> It is recomended that you vacuum analyze every night, do you want to do
> this?
> It is also recomended that you vacuum full every month, do you want to
> do this?
Depends on size/type of database. For large OLTP databases, I recommend
vacuum as often as every 5 mintues, analyze every hour, and Vacuum Full +
Reindex once a week. For a workstation database, your frequencies are
probably OK.
--
Josh Berkus
Aglio Database Solutions
San Francisco
Chris, > > PostgreSQL requires some more shared memory to cache some tables, x Mb, > > do you want to increase your OS kernel parameters? > > > > Tweak shmmax and shmmall > > Note that this still requires a kernel recompile on FreeBSD :( Not our fault, now is it? This would mean that we wouldn't be able to script for FreeBSD. Bug the FreeBSD developers. -- Josh Berkus Aglio Database Solutions San Francisco
Hi, Josh Berkus wrote: > Nick, > > > I reckon do a system scan first, and parse the current PostgreSQL conf > > file to figure out what the settings are. Also back it up with a date > > and time appended to the end to make sure there is a backup before > > overwriting the real conf file. Then a bunch of questions. What sort of > > questions would need to be asked and which parameters would these > > questions affect? So far, and from my limited understanding of the .conf > > file, I reckon there should be the following > > Hmmm ... but I do think that there should be a file to store the user's > previous answers. That way, the script can easily be re-run to fix config > issues. > > > Here is your config of your hardware as detected. Is this correct ? > > > > This could potentially be several questions, i.e. one for proc, mem, > > os, hdd etc > > Would affect shared_buffers, sort_mem, effective_cache_size, > > random_page_cost > > Actually, I think this would break down into: > -- Are Proc & Mem correct? If not, type in correct values > -- Is OS correct? If not, select from list > -- Your HDD: is it: > 1) IDE > 2) Fast multi-disk SCSI or low-end RAID > 3) Medium-to-high-end RAID > > Other things, we don't care about. > > > How was PostgreSQL compiled? > > > > This would be parameters such as the block size and a few other > > compile time parameters. If we can get to some of these read-only > > parameters than that would make this step easier, certainly for the new > > recruits amongst us. > > Actually, from my perspective, we shouldn't bother with this; if an admin > knows enough to set an alternate blaock size for PG, then they know enough to > tweak the Conf file by hand. I think we should just issue a warning that > this script: > 1) does not work for anyone who is using non-default block sizes, > 2) may not work well for anyone using unusual locales, optimization flags, or > other non-default compile options except for language interfaces. > 3) cannot produce good settings for embedded systems; > 4) will not work well for systems which are extremely low on disk space, > memory, or other resouces. > Basically, the script only really needs to work for the people who are > installing PostgreSQL with the default options or from RPM on regular server > or workstation machines with plenty of disk space for normal database > purposes. People who have more complicated setups can read the darned > documentation and tune the conf file by hand. > > > Is PostgreSQL the only thing being run on this computer? > > First, becuase it affects a couple of other variables: > > What kind of database server are you expecting to run? > A) Web Server (many small fast queries from many users, and not much update > activity) > B) Online Transaction Processing (OLTP) database (many small updates > constantly from many users; think "accounting application"). > C) Online Analytical Reporting (OLAP) database (a few large and complicated > read-only queries aggregating large quantites of data for display) > D) Data Transformation tool (loading large amounts of data to process, > transform, and output to other software) > E) Mixed-Use Database Server (a little of all of the above) > F) Workstation (installing this database on a user machine which also has a > desktop, does word processing, etc.) > > If the user answers anything but (F), then we ask: > > Will you be running any other signficant software on this server, such as a > web server, a Java runtime engine, or a reporting application? (yes|no) > > If yes, then: > > How much memory do you expect this other software, in total, to regularly use > while PostgreSQL is in use? (# in MB; should offer default of 50% of the RAM > scanned). > > > How are the clients going to connect? > > > > i.e. TCP or Unix sockets > > We should warn them that they will still need to configure pg_hba.conf. > > > How many clients can connect to this database at once? > > > > Affects max_connections > > Should add a parenthetical comment that for applications which use pooled > connections, or intermittent connection, such as Web applications, the number > of concurrent connections is often much lower than the number of concurrent > users. > > > How many databases and how many tables in each database are going to be > > present? > > > > Affects max_fsm_pages, checkpoint_segments, checkpoint_timeout > > Also need to ask if they have an idea of the total size of all databases, in > MB or GB, which has a stronger relationship to those variables. > Why not to make a cron script that will detect this size fot hil self?In many cases we do not have a good idea how many records(size) will be in data base. > Also, this will give us a chance to check the free space on the PGDATA > partition, and kick the user out with a warning if there is not at least > 2xExpected Size available. > > > Do you want to vacuum you database regularly? > > > > Initial question for cron job > > > > It is recomended that you vacuum analyze every night, do you want to do > > this? > > It is also recomended that you vacuum full every month, do you want to > > do this? > > Depends on size/type of database. For large OLTP databases, I recommend > vacuum as often as every 5 mintues, analyze every hour, and Vacuum Full + > Reindex once a week. For a workstation database, your frequencies are > probably OK. > > -- > Josh Berkus > Aglio Database Solutions > San Francisco > regards,ivan. > ---------------------------(end of broadcast)--------------------------- > TIP 8: explain analyze is your friend
-----Original Message----- From: pgsql-performance-owner@postgresql.org [mailto:pgsql-performance-owner@postgresql.org] On Behalf Of Vivek Khera Sent: Viernes, 10 de Octubre de 2003 03:14 p.m. To: Josh Berkus Cc: pgsql-performance@postgresql.org Subject: Re: [PERFORM] go for a script! / ex: PostgreSQL vs. MySQL >>>>> "JB" == Josh Berkus <josh@agliodbs.com> writes: JB> Vivek, NB> shared_buffers = 1/16th of total memory NB> effective_cache_size = 80% of the supposed kernel cache. >> >> Please take into account the blocksize compiled into PG, too... JB> We can;t change the blocksize in a script that only does the .conf JB> file. Or are you suggesting something else? when you compute optimal shared buffers and effective cache size, these are in terms of blocksize. so if I have 16k block size, you can't compute based on default 8k blocksize. at worst, it would have to be a parameter you pass to the tuning script. ---------------------------(end of broadcast)--------------------------- TIP 7: don't forget to increase your free space map settings
>>>>> "SC" == Sean Chittenden <sean@chittenden.org> writes: >> echo "effective_cache_size = $((`sysctl -n vfs.hibufspace` / 8192))" >> >> I've used it for my dedicated servers. Is this calculation correct? SC> Yes, or it's real close at least. vfs.hibufspace is the amount of SC> kernel space that's used for caching IO operations (minus the I'm just curious if anyone has a tip to increase the amount of memory FreeBSD will use for the cache? It appears to me that even on my 2Gb box, lots of memory is 'free' that could be used for the cache (bumping up shared buffers is another option...) yet the disk is being highly utilized according to systat.
On Monday 13 October 2003 19:34, Vivek Khera wrote: > >>>>> "SC" == Sean Chittenden <sean@chittenden.org> writes: > >> > >> echo "effective_cache_size = $((`sysctl -n vfs.hibufspace` / 8192))" > >> > >> I've used it for my dedicated servers. Is this calculation correct? > > SC> Yes, or it's real close at least. vfs.hibufspace is the amount of > SC> kernel space that's used for caching IO operations (minus the > > I'm just curious if anyone has a tip to increase the amount of memory > FreeBSD will use for the cache? It appears to me that even on my 2Gb > box, lots of memory is 'free' that could be used for the cache > (bumping up shared buffers is another option...) yet the disk is being > highly utilized according to systat. Is this of any help?..reverse video sucks though.. especially spec'ed person like me.. http://unix.derkeiler.com/Mailing-Lists/FreeBSD/performance/2003-07/0073.html Shridhar
> >> echo "effective_cache_size = $((`sysctl -n vfs.hibufspace` / 8192))" > >> > >> I've used it for my dedicated servers. Is this calculation correct? > > SC> Yes, or it's real close at least. vfs.hibufspace is the amount > of SC> kernel space that's used for caching IO operations (minus the > > I'm just curious if anyone has a tip to increase the amount of > memory FreeBSD will use for the cache? Recompile your kernel with BKVASIZE set to 4 times its current value and double your nbuf size. According to Bruce Evans: "Actually there is a way: the vfs_maxbufspace gives the amount of space reserved for buffer kva (= nbuf * BKVASIZE). nbuf is easy to recover from this, and the buffer kva space may be what is wanted anyway." [snip] "I've never found setting nbuf useful, however. I want most parametrized sizes including nbuf to scale with resource sizes, and it's only with RAM sizes of similar sizes to the total virtual address size that its hard to get things to fit. I haven't hit this problem myself since my largest machine has only 1GB. I use an nbuf of something like twice the default one, and a BKVASIZE of 4 times the default. vfs.maxbufspace ends up at 445MB on the machine with 1GB, so it is maxed out now." YMMV. -sc -- Sean Chittenden
> > > PostgreSQL requires some more shared memory to cache some > > > tables, x Mb, do you want to increase your OS kernel parameters? > > > > > > Tweak shmmax and shmmall > > > > Note that this still requires a kernel recompile on FreeBSD :( > > Not our fault, now is it? This would mean that we wouldn't be able > to script for FreeBSD. Bug the FreeBSD developers. And if you do so, you're going to hear that shm* is an antiquated interface that's dated, slow, inefficient and shouldn't be used. :) Every few months one of the uber core BSD hackers threatens to rewrite that part of PG because high up in the BSD camp, it's common belief that shm* is a source of performance loss for PostgreSQL. One of these days it'll happen, probably with mmap() mmap()'ing MAP_SHARED files stored in a $PGDATA/data/shared dir as mmap() is by far and away the fastest shared memory mechanism and certainly is very widely deployed (I would be surprised if any of the supported PG platforms didn't have mmap()). -sc -- Sean Chittenden
>>>>> "JB" == Josh Berkus <josh@agliodbs.com> writes: JB> Chris, >> > PostgreSQL requires some more shared memory to cache some tables, x Mb, >> > do you want to increase your OS kernel parameters? >> > >> > Tweak shmmax and shmmall >> >> Note that this still requires a kernel recompile on FreeBSD :( JB> Not our fault, now is it? This would mean that we wouldn't be JB> able to script for FreeBSD. Bug the FreeBSD developers. "I read it on the net so it must be true" applies here. You /can/ set these values via sysctl calls. -- =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Vivek Khera, Ph.D. Khera Communications, Inc. Internet: khera@kciLink.com Rockville, MD +1-240-453-8497 AIM: vivekkhera Y!: vivek_khera http://www.khera.org/~vivek/
>>>>> "CK" == Christopher Kings-Lynne <chriskl@familyhealth.com.au> writes: >> If shmmax and shmmall are too small, then: >> PostgreSQL requires some more shared memory to cache some tables, x >> Mb, do you want to increase your OS kernel parameters? >> Tweak shmmax and shmmall CK> Note that this still requires a kernel recompile on FreeBSD :( According to whom? sysctl is your friend. Some sysctl settings may require reboot, but I don't think the SHM ones do. -- =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Vivek Khera, Ph.D. Khera Communications, Inc. Internet: khera@kciLink.com Rockville, MD +1-240-453-8497 AIM: vivekkhera Y!: vivek_khera http://www.khera.org/~vivek/
Sean Chittenden <sean@chittenden.org> writes:
> Every few months one of the uber core BSD hackers threatens to rewrite
> that part of PG because high up in the BSD camp, it's common belief
> that shm* is a source of performance loss for PostgreSQL.
They're full of it. RAM is RAM, no? Once you've got the memory mapped
into your address space, it's hard to believe that it matters how you
got hold of it.
In any case, mmap doesn't have the semantics we need. See past
discussions.
regards, tom lane
Centuries ago, Nostradamus foresaw when khera@kcilink.com (Vivek Khera) would write: >>>>>> "JB" == Josh Berkus <josh@agliodbs.com> writes: > > JB> Chris, >>> > PostgreSQL requires some more shared memory to cache some tables, x Mb, >>> > do you want to increase your OS kernel parameters? >>> > >>> > Tweak shmmax and shmmall >>> >>> Note that this still requires a kernel recompile on FreeBSD :( > > JB> Not our fault, now is it? This would mean that we wouldn't be > JB> able to script for FreeBSD. Bug the FreeBSD developers. > > "I read it on the net so it must be true" applies here. You /can/ set > these values via sysctl calls. Yes, indeed, sysctl can tweak these values fairly adequately. Now, numbers of semaphors are not as readily tweaked; I wound up limited, the other day, when I tried setting values for... kern.ipc.semmns kern.ipc.semmni -- let name="cbbrowne" and tld="ntlug.org" in String.concat "@" [name;tld];; http://www.ntlug.org/~cbbrowne/x.html "So, when you typed in the date, it exploded into a sheet of blue flame and burned the entire admin wing to the ground? Yes, that's a known bug. We'll be fixing it in the next release. Until then, try not to use European date format, and keep an extinguisher handy." -- slam@pobox.com (Tequila Rapide)
>>>If shmmax and shmmall are too small, then: >>>PostgreSQL requires some more shared memory to cache some tables, x >>>Mb, do you want to increase your OS kernel parameters? >>>Tweak shmmax and shmmall > > > CK> Note that this still requires a kernel recompile on FreeBSD :( > > According to whom? sysctl is your friend. Some sysctl settings may > require reboot, but I don't think the SHM ones do. Hmmm...you may be right - I can't prove it now... houston# sysctl -w kern.ipc.shmmax=99999999999 kern.ipc.shmmax: 33554432 -> 2147483647 Hrm. Ok. Maybe they've changed that in some recent version :) Chris
> > Yes, indeed, sysctl can tweak these values fairly adequately. > > Now, numbers of semaphors are not as readily tweaked; I wound up > limited, the other day, when I tried setting values for... > > kern.ipc.semmns > kern.ipc.semmni Same. Maybe that was the option I was thinking was read-only: houston# sysctl kern.ipc.semmns kern.ipc.semmns: 60 houston# sysctl -w kern.ipc.semmns=70 sysctl: oid 'kern.ipc.semmns' is read only houston# sysctl kern.ipc.semmni kern.ipc.semmni: 10 houston# sysctl -w kern.ipc.semmni=30 sysctl: oid 'kern.ipc.semmni' is read only I like how they use oids :P Chris
> Date: Sun, 12 Oct 2003 13:30:45 -0700 > From: Josh Berkus <josh@agliodbs.com> > To: Nick Barr <nicky@chuckie.co.uk> > Cc: pgsql-performance@postgresql.org > Subject: Re: go for a script! / ex: PostgreSQL vs. MySQL > Message-ID: <200310121330.45115.josh@agliodbs.com> > >> This would be parameters such as the block size and a few other >> compile time parameters. If we can get to some of these read-only >> parameters than that would make this step easier, certainly for the new >> recruits amongst us. > > Actually, from my perspective, we shouldn't bother with this; if an admin > knows enough to set an alternate blaock size for PG, then they know > enough to tweak the Conf file by hand. I think we should just issue a > warning that this script: > 1) does not work for anyone who is using non-default block sizes, There was some talk, either on this list or freebsd-performance about setting the default block size for PostgreSQL running on FreeBSD to be 16k because of performance reasons. That is: *default* for the port, user is not asked. So an automagical method to scale non-default block sizes is a very needed thing. > 2) may not work well for anyone using unusual locales, optimization > flags, or other non-default compile options except for language > interfaces. Depends on what you consider 'unusual'? I hope not things like iso8859-x (or, to be exact, European languages) :) -- Logic is a systematic method of coming to the wrong conclusion with confidence.
Ivan, > There was some talk, either on this list or freebsd-performance about > setting the default block size for PostgreSQL running on FreeBSD to be 16k > because of performance reasons. That is: *default* for the port, user is > not asked. So an automagical method to scale non-default block sizes is a > very needed thing. Hmmm ... possibly. My concern is that if someone uses a very non-default value, such as 256K, then they are probably better off doing their own tuning because they've got an unusual system. However, we could easily limit it to the range of 4K to 32K. Of course, since there's no GUC var, we'd have to ask the user to confirm their block size. I'm reluctant to take this approach because if the user gets it wrong, then the settings will be *way* off ... and possibly cause PostgreSQL to be unrunnable or have "out of memory" crashes. Unless there's a way to find it in the compiled source? > > 2) may not work well for anyone using unusual locales, optimization > > flags, or other non-default compile options except for language > > interfaces. > > Depends on what you consider 'unusual'? I hope not things like iso8859-x > (or, to be exact, European languages) :) On second thought, I'm not sure what an "unusual locale" would be. Scratch that. -- Josh Berkus Aglio Database Solutions San Francisco
Josh Berkus <josh@agliodbs.com> writes:
> Unless there's a way to find it in the compiled source?
See pg_controldata.
regards, tom lane
> >> This would be parameters such as the block size and a few > >> other compile time parameters. If we can get to some of these > >> read-only parameters than that would make this step easier, > >> certainly for the new recruits amongst us. > > > > Actually, from my perspective, we shouldn't bother with this; if an admin > > knows enough to set an alternate blaock size for PG, then they know > > enough to tweak the Conf file by hand. I think we should just issue a > > warning that this script: > > 1) does not work for anyone who is using non-default block sizes, > > There was some talk, either on this list or freebsd-performance > about setting the default block size for PostgreSQL running on > FreeBSD to be 16k because of performance reasons. That is: *default* > for the port, user is not asked. Real quick, this isn't true, the block size is tunable, but does not change the default. You can set PGBLOCKSIZE to the values "16K" or "32K" to change the block size, but the default remains 8K. http://lists.freebsd.org/pipermail/freebsd-database/2003-October/000111.html -sc -- Sean Chittenden