Re: Avoiding repeated snapshot computation - Mailing list pgsql-hackers
| From | Gurjeet Singh |
|---|---|
| Subject | Re: Avoiding repeated snapshot computation |
| Date | |
| Msg-id | CABwTF4UhinaNb+jPTVmcznew1d7HstH8Nqw9t0Ag86tCYji-QQ@mail.gmail.com Whole thread Raw |
| In response to | Re: Avoiding repeated snapshot computation (Andres Freund <andres@anarazel.de>) |
| Responses |
Re: Avoiding repeated snapshot computation
Re: Avoiding repeated snapshot computation |
| List | pgsql-hackers |
On Sat, Nov 26, 2011 at 6:51 PM, Andres Freund <andres@anarazel.de> wrote:
This may not be necessary, but can you please share the modified config you used for the last run.
I tabulated your last results to make it more readable, and added columns to show the improvement.
origsnap reordersnap diff %age improvementOn Saturday, November 26, 2011 11:39:23 PM Robert Haas wrote:> On Sat, Nov 26, 2011 at 5:28 PM, Andres Freund <andres@anarazel.de> wrote:Being prodded like that I ran a very quick benchmark on my workstation.
> > On Saturday, November 26, 2011 09:52:17 PM Tom Lane wrote:
> >> I'd just as soon keep the fields in a logical order.
> >
> > Btw, I don't think the new order is necessarily worse than the old one.
>
> You forget to attach the benchmark results.
>
> My impression is that cache lines on modern hardware are 64 or 128
> *bytes*, in which case this wouldn't matter a bit.
>
> But testing is even better than guessing.
Unfortunately that means I cannot work during the time which is why I kept it
rather short...
That machine has 2 E5520@2.27GHz which means 2(sockets) * 4(cores) *
2(threads) and 24GB of ram.
Data was initialized with: pgbench -h /tmp/ --unlogged-tables -i -s 20 pgbench
pgbench -h /tmp/ pgbench -S -j 16 -c 16 -T 60
origsnap: 92825.743958 93145.110901 93389.915474 93175.482351
reordersnap: 93560.183272 93613.333494 93495.263012 93523.368489
pgbench -h /tmp/ pgbench -S -j 32 -c 32 -T 60
origsnap: 81846.743329 81545.175672 81702.755226 81576.576435
81228.154119 81546.047708 81421.436262
reordersnap: 81823.479196 81787.784508 81820.242145 81790.263415
81762.421592 81496.333144 81732.088876
At that point I noticed I had accidentally run with a nearly stock config...
An even shorter run with a more approrioate config yielded:
pgbench -h /tmp/ pgbench -S -j 32 -c 32 -T 20
origsnap: 102234.664020 102003.449741 102119.509053 101722.410387
101973.651318 102056.440561
reordersnap: 103444.877879 103385.888808 103302.318923 103372.659486
103330.157612 103313.833821
Looks like a win to me. Even on this comparatively small machine.
This may not be necessary, but can you please share the modified config you used for the last run.
I tabulated your last results to make it more readable, and added columns to show the improvement.
------------------------------------------------------------------
102234.66402 103444.877879 1210.213859 1.1837607827
102003.449741 103385.888808 1382.439067 1.3552865815
102119.509053 103302.318923 1182.80987 1.1582604352
101722.410387 103372.659486 1650.249099 1.6223063263
101973.651318 103330.157612 1356.506294 1.3302517626
102056.440561 103313.833821 1257.39326 1.2320567454
That looks like a win to me too. We're getting a little over 1% improvement for free!
Maybe submitting this patch to the commitfest might help get some serious consideration from a reviewer.
Regards,
--
Gurjeet Singh
EnterpriseDB Corporation
The Enterprise PostgreSQL Company
EnterpriseDB Corporation
The Enterprise PostgreSQL Company
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