Thread: work_mem / maintenance_work_mem maximums
Greetings, After watching a database import go abysmally slow on a pretty beefy box with tons of RAM, I got annoyed and went to huntdown why in the world PG wasn't using but a bit of memory. Turns out to be a well known and long-standing issue: http://www.mail-archive.com/pgsql-hackers@postgresql.org/msg101139.html Now, we could start by fixing guc.c to correctly have the max value for these be MaxAllocSize/1024, for starters, then atleast our users would know when they set a higher value it's not going to be used. That, in my mind, is a pretty clearbug fix. Of course, that doesn't help us poor data-warehousing bastards with 64G+ machines. Sooo.. I don't know much about what the limit is or why it's there, but based on the comments, I'm wondering if we couldjust move the limit to a more 'sane' place than the-function-we-use-to-allocate. If we need a hard limit due to TOAST,let's put it there, but I'm hopeful we could work out a way to get rid of this limit in repalloc and that we can letsorts and the like (uh, index creation) use what memory the user has decided it should be able to. Thanks, Stephen
Stephen Frost wrote: -- Start of PGP signed section. > Greetings, > > After watching a database import go abysmally slow on a pretty beefy > box with tons of RAM, I got annoyed and went to hunt down why in the > world PG wasn't using but a bit of memory. Turns out to be a well > known and long-standing issue: > > http://www.mail-archive.com/pgsql-hackers@postgresql.org/msg101139.html > > Now, we could start by fixing guc.c to correctly have the max value > for these be MaxAllocSize/1024, for starters, then at least our users > would know when they set a higher value it's not going to be used. > That, in my mind, is a pretty clear bug fix. Of course, that doesn't > help us poor data-warehousing bastards with 64G+ machines. > > Sooo.. I don't know much about what the limit is or why it's there, > but based on the comments, I'm wondering if we could just move the > limit to a more 'sane' place than the-function-we-use-to-allocate. If > we need a hard limit due to TOAST, let's put it there, but I'm hopeful > we could work out a way to get rid of this limit in repalloc and that > we can let sorts and the like (uh, index creation) use what memory the > user has decided it should be able to. Is this a TODO? Can we easily fix the tuplesort.c code? -- Bruce Momjian <bruce@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + It's impossible for everything to be true. +
> Is this a TODO? Can we easily fix the tuplesort.c code?
Easily, no. But that's not a reason for it to not be a TODO.
I, too, would like to be able to make use of 32GB of work_mem effectively.
-- -- Josh Berkus PostgreSQL Experts Inc.
http://www.pgexperts.com
Josh Berkus wrote: > > > Is this a TODO? Can we easily fix the tuplesort.c code? > > Easily, no. But that's not a reason for it to not be a TODO. > > I, too, would like to be able to make use of 32GB of work_mem effectively. [ repost to the right thread.] Well, I figure it will be hard to allow larger maximums, but can we make the GUC variable maximums be more realistic? Right now it is MAX_KILOBYTES (INT_MAX). -- Bruce Momjian <bruce@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + It's impossible for everything to be true. +