Re: [HACKERS] POSIX shared memory support - Mailing list pgsql-patches
From | Chris Marcellino |
---|---|
Subject | Re: [HACKERS] POSIX shared memory support |
Date | |
Msg-id | 9C09B71B-C325-4720-A348-11DB9179E46D@apple.com Whole thread Raw |
List | pgsql-patches |
Yes, that is understandable. I'm not sure that there is a robust portable solution that doesn't involve a major rearchitecture. I'm not sure that would be worth the risk given the reward. Thanks, Chris On Apr 2, 2008, at 8:50 AM, Bruce Momjian wrote: > > The original patch author: > > Chris Marcellino <cmarcellino@apple.com> > > was not CC'ed as part of this email thread. That was a mistake. > Chris, > the email thread discussing your patch is here: > > http://archives.postgresql.org/pgsql-hackers/2008-03/ > msg01262.php > > Please read the discussion --- the bottom line is that there isn't > much > support for the patch. Magnus was able to do the POSIX usage without > relying on shared memory, but I just talked to him via IM and he > said it > used a Win32-specific feature that isn't portable to Unix. > > I am holding this patch for the next commit fest in hopes you can > adjust > it, but if not the patch will be rejected at that time. > > --------------------------------------------------------------------------- > > Stephen Frost wrote: > -- Start of PGP signed section. >> Chris, et al, >> >> (commit-fest consensus discussion) >> * Chris Marcellino wrote: >>> In case you haven't had enough, here is another version of the code >>> to make Postgres use POSIX shared memory. Along with the issues that >>> have already been addressed, this version ensures that orphaned >>> backends are not in the database when restarting Postgres by using a >>> single 1 byte SysV segment to see who is attached to the segment >>> using shmctl/IPC_STAT/nattach. >> >> This really feels like a deal-breaker to me. My first reaction to >> this >> patch, honestly, is that it's being justified for all the wrong >> reasons. >> Changing to POSIX shm seems like a reasonable goal in general, >> provided >> it can do what we need, but doing it to work around silly defaults >> doesn't really work for me. If the real issue you have is with the >> SysV >> limits then I'd suggest you bring that up with the kernel/ >> distribution >> folks to get them to use something more sane. >> >> Looking around a bit, it looks like it's already being addressed in >> some >> places, for example Solaris 10 apparently uses 1/4th of memory, while >> Centos 5 uses 4GB. Suse also uses a larger default, from what I >> understand. Supporting this effort to get it raised on various >> platforms and distributions seems like a much better approach. >> >> Additionally, it strikes me that there *is* a limit on POSIX shared >> memory too, generally half of ram on the systems I've looked at, but >> there's no guarentee that'll always be the default or that half of >> ram >> will always be enough for us. So, even with this change, the problem >> isn't completely 'solved'. >> >> Finding a way for POSIX shm to do what we need, including Tom's >> concerns, without depending on SvsV shm as a crutch work around, >> would >> make this change much more reasonable and could be justified as >> moving >> to a well defined POSIX standard, and means we may be able to support >> platforms which either are new and don't implement SysV but just >> POSIX, >> or cases where SysV is being actively depreceated. Neither of >> which is >> possible if we're stuck with using it in some cases. >> >> Thanks, >> >> Stephen > -- End of PGP section, PGP failed! > > -- > Bruce Momjian <bruce@momjian.us> http://momjian.us > EnterpriseDB http://enterprisedb.com > > + If your life is a hard drive, Christ can be your backup. +
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