Stefan Kaltenbrunner <stefan@kaltenbrunner.cc> wrote:
> A 25-30% performance regression in our main bulk loading mechanism
> should at least be explained before the release...
I think a performance regression of that magnitude merits holding up
a release to resolve.
Note that in a follow-up post showing the slow 8.4 copying on Linux,
the copy was 11.7% to 19.3% *faster* on 8.4 when the WAL writing was
suppressed:
http://archives.postgresql.org/pgsql-performance/2009-06/msg00219.php
Extracting from that post:
# I can reproduce that on Linux(CentoS 5.3/x86_64, Nehalem Xeon E5530)
# on 8.4 I get:
#
# 3m59/4m01/3m56s runtime and a profile of
#
# samples % symbol name
# 636302 19.6577 XLogInsert
# 415510 12.8366 CopyReadLine
# on 8.3.7 I get 2m58s,2m54s,2m55s
#
# and a profile of:
#
# samples % symbol name
# 460966 16.2924 XLogInsert
# 307386 10.8643 CopyReadLine
# If I do the same test utilizing WAL bypass the picture changes:
#
# 8.3 runtimes:2m16,2min14s,2min22s
# 8.4 runtime: 2m1s,2m,1m59s
Is there a reason to believe that the XLogInsert part of this *only*
affects bulk loads?
-Kevin