On Wed, Aug 7, 2013 at 07:04:43PM +0100, Thom Brown wrote:
On 7 August 2013 18:49, Jon Nelson wrote:
On Wed, Aug 7, 2013 at 12:42 PM, Thom Brown wrote:
for i in 1 2 5 10 100; do ./test_fallocate foo $i 1; done
method: classic. 1 open/close iterations, 1 rewrite in 0.6380s
method: posix_fallocate. 1 open/close iterations, 1 rewrite in 0.3204s
method: glibc emulation. 1 open/close iterations, 1 rewrite in 0.6274s
method: classic. 2 open/close iterations, 1 rewrite in 1.2908s
method: posix_fallocate. 2 open/close iterations, 1 rewrite in 0.6596s
method: glibc emulation. 2 open/close iterations, 1 rewrite in 1.2666s
method: classic. 5 open/close iterations, 1 rewrite in 3.1419s
method: posix_fallocate. 5 open/close iterations, 1 rewrite in 1.5930s
method: glibc emulation. 5 open/close iterations, 1 rewrite in 3.1516s
method: classic. 10 open/close iterations, 1 rewrite in 6.2912s
method: posix_fallocate. 10 open/close iterations, 1 rewrite in 3.2626s
method: glibc emulation. 10 open/close iterations, 1 rewrite in 6.3667s
method: classic. 100 open/close iterations, 1 rewrite in 67.4174s
method: posix_fallocate. 100 open/close iterations, 1 rewrite in 37.8788s
method: glibc emulation. 100 open/close iterations, 1 rewrite in 55.0714s
OK. That's interesting, and a good data point.

One thing you could try manually disabling the use of posix_fallocate in 269e78.
After running ./configure --stuff-here
edit src/include/pg_config.h and comment out the following line (on or
around line 374)
#define HAVE_POSIX_FALLOCATE 1

*then* build postgresql and see if the performance hit is still there.
Okay, done that. The TPS increases again:

2308.807568 / 2554.264572 / 2563.190204

And I did run ./configure... before removing the line, and built it
after the change.
Where are we on this issue?

--
   Bruce Momjian <bruce@momjian.us> http://momjian.us
   EnterpriseDB http://enterprisedb.com

   + It's impossible for everything to be true. +

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