Re: Questions about tuning on FreeBSD... - Mailing list pgsql-general
From | postgres@vsservices.com |
---|---|
Subject | Re: Questions about tuning on FreeBSD... |
Date | |
Msg-id | 01091023443406.73075@prime.vsservices.com Whole thread Raw |
In response to | Questions about tuning on FreeBSD... (Philip Hallstrom <philip@adhesivemedia.com>) |
List | pgsql-general |
On Monday 10 September 2001 18:52, Philip Hallstrom wrote: > Hi all - > I have some questions about tuning the various kernel parameters > on FreeBSD. I've read Bruce's article a couple of times and the various > parts of the documentation, but I still have some questions and was hoping > people here could confirm/deny my assumptions. > > The machine in question has 512 megs of ram and doesn't do anything else > significant other than postgresql. > Depending on the size of your DB, this should do OK... > As I understand there are two major tuneable parameters: > > - shared buffer cache: which I can think of as a sort of RAM-based > disk cache of recently accessed tables (or parts of tables). Ideally this > would be large enough to hold the entire database. The goal is to make > this large enough to hold the most commonly accessed tables. I run with shared buffers = 5120 > - sort memory batch size: this is the amount of memory that *each backend* > uses to do it's sorts/merges/joins. If the backend needs more than this > then it writes to temporary files. Again the goal would be to make all > your sorts/merges/joins fit in this size. Sort Mem = 4096 > The overall goal is to give enough memory to postgresql so that it writes > to disk as little as possible while making sure that the OS as a whole > doesn't have to start swapping. So as a starting point could one install > the OS, let it run for a bit, see how much memory it's using, see how much > memory is left and assign most of that to postgresql? > > > Regarding the KERNEL parameters. I can follow the general rules mentioned > in the docs for configuring things no problem. However is there any > danger in doing that? Can they be too big? Or can they only be too big > in conjunction with giving postgresql too much memory? In otherwords if I > set them to something, but don't run postgresql have I affected how the OS > will run by itself? > > Is there a way to determine the maximum number of backends that can be run > given a given amount of RAM? > > Also, if anyone has a Free# SYSV stuff BSD box with 512 ram, what are your > kernel settings? options SYSVSHM #SYSV-style shared memory options SHMMAXPGS=12288 options SHMMAX="(SHMMAXPGS*PAGE_SIZE+1)" options SHMSEG=256 options SHMMNI=512 options SHMMIN=1 options SYSVMSG #SYSV-style message queues options SYSVSEM #SYSV-style semaphores options SEMMNI=256 options SEMMNS=512 options SEMMNU=256 options SEMMAP=256 Note: Some of these might be WAY TOO high! I could not find enough docs to tell me, so I just added extra everywhere.... Maybe some of the experts can pick this apart... > > Thanks! > > -philip > > On that note: Could some of the PostgreSQL expert take a look my number of buffers and the kernel config and tell me if I'm running too much of anything? GB -- GB Clark II | Roaming FreeBSD Admin gclarkii@VSServices.COM | General Geek CTHULU for President - Why choose the lesser of two evils?
pgsql-general by date: