On Mon, Apr 11, 2016 at 8:10 AM, Andres Freund <and...@anarazel.de> wrote:
> On 2016-04-10 09:03:37 +0300, Alexander Korotkov wrote: > > 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... > > Could you retry after applying the attached series of patches? > Yes, I will try with these patches and snapshot too old reverted. ------ Alexander Korotkov Postgres Professional: http://www.postgrespro.com The Russian Postgres Company
