Re: [PERFORM] a question about Direct I/O and double buffering

2007-04-18 Thread Jim C. Nasby
On Thu, Apr 05, 2007 at 03:10:43PM -0500, Erik Jones wrote: > Nope. What we never tracked down was the factor of 10 drop in > database transactions, not disk transactions. The write volume was > most definitely due to the direct io setting -- writes are now being > done in terms of the syst

Re: [PERFORM] a question about Direct I/O and double buffering

2007-04-05 Thread david
On Thu, 5 Apr 2007, Erik Jones wrote: On Apr 5, 2007, at 3:33 PM, [EMAIL PROTECTED] wrote: On Thu, 5 Apr 2007, Xiaoning Ding wrote: > > > > To the best of my knowledge, Postgres itself does not have a direct IO > > option (although it would be a good addition). So, in order to use > > d

Re: [PERFORM] a question about Direct I/O and double buffering

2007-04-05 Thread david
On Thu, 5 Apr 2007, Xiaoning Ding wrote: > Xiaoning > Looks like it. I just did a cursory search of the archives and it seems > that others have looked at this before so you'll probably want to start > there if your up to it. > Linux used to have (still does?) a RAW interface which might

Re: [PERFORM] a question about Direct I/O and double buffering

2007-04-05 Thread Erik Jones
On Apr 5, 2007, at 3:33 PM, [EMAIL PROTECTED] wrote: On Thu, 5 Apr 2007, Xiaoning Ding wrote: To the best of my knowledge, Postgres itself does not have a direct IO option (although it would be a good addition). So, in order to use direct IO with postgres you'll need to consult your

Re: [PERFORM] a question about Direct I/O and double buffering

2007-04-05 Thread Alex Deucher
On 4/5/07, Xiaoning Ding <[EMAIL PROTECTED]> wrote: Alex Deucher wrote: > On 4/5/07, Erik Jones <[EMAIL PROTECTED]> wrote: >> >> On Apr 5, 2007, at 1:22 PM, Xiaoning Ding wrote: >> >> Erik Jones wrote: >> On Apr 5, 2007, at 12:09 PM, Xiaoning Ding wrote: >> Hi, >> >> A page may be double buffered

Re: [PERFORM] a question about Direct I/O and double buffering

2007-04-05 Thread Xiaoning Ding
Alex Deucher wrote: On 4/5/07, Erik Jones <[EMAIL PROTECTED]> wrote: On Apr 5, 2007, at 1:22 PM, Xiaoning Ding wrote: Erik Jones wrote: On Apr 5, 2007, at 12:09 PM, Xiaoning Ding wrote: Hi, A page may be double buffered in PG's buffer pool and in OS's buffer cache. Other DBMS like DB2 and Or

Re: [PERFORM] a question about Direct I/O and double buffering

2007-04-05 Thread david
On Thu, 5 Apr 2007, Xiaoning Ding wrote: To the best of my knowledge, Postgres itself does not have a direct IO option (although it would be a good addition). So, in order to use direct IO with postgres you'll need to consult your filesystem docs for how to set the forcedirectio mount opti

Re: [PERFORM] a question about Direct I/O and double buffering

2007-04-05 Thread Erik Jones
On Apr 5, 2007, at 2:56 PM, Mark Lewis wrote: ... [snipped for brevity] ... Not to hijack this thread, but has anybody here tested the behavior of PG on a file system with OS-level caching disabled via forcedirectio or by using an inherently non-caching file system such as ocfs2? I've been

Re: [PERFORM] a question about Direct I/O and double buffering

2007-04-05 Thread Mark Lewis
... [snipped for brevity] ... > > > Not to hijack this thread, but has anybody here tested the behavior > > of > > PG on a file system with OS-level caching disabled via forcedirectio > > or > > by using an inherently non-caching file system such as ocfs2? > > > > > > I've been thinking about tr

Re: [PERFORM] a question about Direct I/O and double buffering

2007-04-05 Thread Erik Jones
On Apr 5, 2007, at 1:27 PM, Mark Lewis wrote: On Thu, 2007-04-05 at 13:09 -0500, Erik Jones wrote: On Apr 5, 2007, at 12:09 PM, Xiaoning Ding wrote: Hi, A page may be double buffered in PG's buffer pool and in OS's buffer cache. Other DBMS like DB2 and Oracle has provided Direct I/O option

Re: [PERFORM] a question about Direct I/O and double buffering

2007-04-05 Thread Alex Deucher
On 4/5/07, Erik Jones <[EMAIL PROTECTED]> wrote: On Apr 5, 2007, at 1:22 PM, Xiaoning Ding wrote: Erik Jones wrote: On Apr 5, 2007, at 12:09 PM, Xiaoning Ding wrote: Hi, A page may be double buffered in PG's buffer pool and in OS's buffer cache. Other DBMS like DB2 and Oracle has provided Dire

Re: [PERFORM] a question about Direct I/O and double buffering

2007-04-05 Thread Erik Jones
On Apr 5, 2007, at 1:22 PM, Xiaoning Ding wrote: Erik Jones wrote: On Apr 5, 2007, at 12:09 PM, Xiaoning Ding wrote: Hi, A page may be double buffered in PG's buffer pool and in OS's buffer cache. Other DBMS like DB2 and Oracle has provided Direct I/O option to eliminate double buffering

Re: [PERFORM] a question about Direct I/O and double buffering

2007-04-05 Thread Mark Lewis
Not to hijack this thread, but has anybody here tested the behavior of PG on a file system with OS-level caching disabled via forcedirectio or by using an inherently non-caching file system such as ocfs2? I've been thinking about trying this setup to avoid double-caching now that the 8.x series sc

Re: [PERFORM] a question about Direct I/O and double buffering

2007-04-05 Thread Xiaoning Ding
Erik Jones wrote: On Apr 5, 2007, at 12:09 PM, Xiaoning Ding wrote: Hi, A page may be double buffered in PG's buffer pool and in OS's buffer cache. Other DBMS like DB2 and Oracle has provided Direct I/O option to eliminate double buffering. I noticed there were discusses on the list. But I c

Re: [PERFORM] a question about Direct I/O and double buffering

2007-04-05 Thread Erik Jones
On Apr 5, 2007, at 12:09 PM, Xiaoning Ding wrote: Hi, A page may be double buffered in PG's buffer pool and in OS's buffer cache. Other DBMS like DB2 and Oracle has provided Direct I/O option to eliminate double buffering. I noticed there were discusses on the list. But I can not find simi

[PERFORM] a question about Direct I/O and double buffering

2007-04-05 Thread Xiaoning Ding
Hi, A page may be double buffered in PG's buffer pool and in OS's buffer cache. Other DBMS like DB2 and Oracle has provided Direct I/O option to eliminate double buffering. I noticed there were discusses on the list. But I can not find similar option in PG. Does PG support direct I/O now? The tu