On Sun, Apr 10, 2016 at 8:36 AM, Alexander Korotkov < a.korot...@postgrespro.ru> wrote:
> On Sat, Apr 9, 2016 at 10:49 PM, Andres Freund <and...@anarazel.de> wrote: > >> >> >> On April 9, 2016 12:43:03 PM PDT, Andres Freund <and...@anarazel.de> >> wrote: >> >On 2016-04-09 22:38:31 +0300, Alexander Korotkov wrote: >> >> There are results with 5364b357 reverted. >> > >> >Crazy that this has such a negative impact. Amit, can you reproduce >> >that? Alexander, I guess for r/w workload 5364b357 is a benefit on that >> >machine as well? >> >> How sure are you about these measurements? > > > I'm pretty sure. I've retried it multiple times by hand before re-run the > script. > > >> Because there really shouldn't be clog lookups one a steady state is >> reached... >> > > Hm... I'm also surprised. There shouldn't be clog lookups once hint bits > are set. > I also tried to run perf top during pgbench and get some interesting results. Without 5364b357: 5,69% postgres [.] GetSnapshotData 4,47% postgres [.] LWLockAttemptLock 3,81% postgres [.] _bt_compare 3,42% postgres [.] hash_search_with_hash_value 3,08% postgres [.] LWLockRelease 2,49% postgres [.] PinBuffer.isra.3 1,58% postgres [.] AllocSetAlloc 1,17% [kernel] [k] __schedule 1,15% postgres [.] PostgresMain 1,13% libc-2.17.so [.] vfprintf 1,01% libc-2.17.so [.] __memcpy_ssse3_back With 5364b357: 18,54% postgres [.] GetSnapshotData 3,45% postgres [.] LWLockRelease 3,27% postgres [.] LWLockAttemptLock 3,21% postgres [.] _bt_compare 2,93% postgres [.] hash_search_with_hash_value 2,00% postgres [.] PinBuffer.isra.3 1,32% postgres [.] AllocSetAlloc 1,10% libc-2.17.so [.] vfprintf Very surprising. It appears that after 5364b357, GetSnapshotData consumes more time. But I can't see anything depending on clog buffers in GetSnapshotData code... ------ Alexander Korotkov Postgres Professional: http://www.postgrespro.com The Russian Postgres Company
