On 25 February 2016 at 18:42, Amit Kapila <amit.kapil...@gmail.com> wrote:
> On Thu, Feb 25, 2016 at 11:38 PM, Simon Riggs <si...@2ndquadrant.com> > wrote: > >> On 24 February 2016 at 23:26, Amit Kapila <amit.kapil...@gmail.com> >> wrote: >> >>> From past few weeks, we were facing some performance degradation in the >>> read-only performance bench marks in high-end machines. My colleague >>> Mithun, has tried by reverting commit ac1d794 which seems to degrade the >>> performance in HEAD on high-end m/c's as reported previously[1], but still >>> we were getting degradation, then we have done some profiling to see what >>> has caused it and we found that it's mainly caused by spin lock when >>> called via pin/unpin buffer and then we tried by reverting commit 6150a1b0 >>> which has recently changed the structures in that area and it turns out >>> that reverting that patch, we don't see any degradation in performance. >>> The important point to note is that the performance degradation doesn't >>> occur every time, but if the tests are repeated twice or thrice, it >>> is easily visible. >>> >> >> Not seen that on the original patch I posted. 6150a1b0 contains multiple >> changes to the lwlock structures, one written by me, others by Andres. >> >> Perhaps we should revert that patch and re-apply the various changes in >> multiple commits so we can see the differences. >> >> > Yes, thats one choice, other is locally we can narrow down the root cause > of problem and then try to address the same. Last time similar issue came > up on list, agreement [1] was to note down it in PostgreSQL 9.6 open items > and then work on it. I think for this problem, we haven't got to the root > cause of problem, so we can try to investigate it. If nobody else steps up > to reproduce and look into problem, in few days, I will look into it. > > [1] - > http://www.postgresql.org/message-id/CA+TgmoYjYqegXzrBizL-Ov7zDsS=GavCnxYnGn9WZ1S=rp8...@mail.gmail.com > Don't understand this. If a problem is caused by one of two things, first you check one, then the other. -- Simon Riggs http://www.2ndQuadrant.com/ <http://www.2ndquadrant.com/> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
