Re: POC: Cache data in GetSnapshotData()
| От | Amit Kapila |
|---|---|
| Тема | Re: POC: Cache data in GetSnapshotData() |
| Дата | |
| Msg-id | CAA4eK1JD=ta9thMfGfHx06hkK9qf1W5RXWuxwYW8r9YnHzPq0Q@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: POC: Cache data in GetSnapshotData() (Mithun Cy <mithun.cy@enterprisedb.com>) |
| Ответы |
Re: POC: Cache data in GetSnapshotData()
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| Список | pgsql-hackers |
On Thu, Mar 10, 2016 at 1:04 PM, Mithun Cy <mithun.cy@enterprisedb.com> wrote:
On Thu, Mar 3, 2016 at 11:50 PM, Robert Haas <robertmhaas@gmail.com> wrote:
>What if you apply both this and Amit's clog control log patch(es)? Maybe the combination of the two helps substantially more than either >one alone.I did the above tests along with Amit's clog patch. Machine :8 socket, 64 core. 128 hyperthread.With clog changes, perf of caching the snapshot patch improves.
clients BASE ONLY CLOG CHANGES % Increase ONLY SAVE SNAPSHOT % Increase CLOG CHANGES + SAVE SNAPSHOT % Increase 64 29247.658034 30855.728835 5.4981181711 29254.532186 0.0235032562 32691.832776 11.7758992463 88 31214.305391 33313.393095 6.7247618606 32109.248609 2.8670931702 35433.655203 13.5173592978 128 30896.673949 34015.362152 10.0939285832 *** *** 34947.296355 13.110221549 256 27183.780921 31192.895437 14.7481857938 *** *** 32873.782735 20.9316056164
This data looks promising to me and indicates that saving the snapshot has benefits and we can see noticeable performance improvement especially once the CLog contention gets reduced. I wonder if we should try these tests with unlogged tables, because I suspect most of the contention after CLogControlLock and ProcArrayLock is for WAL related locks, so you might be able to see better gain with these patches. Do you think it makes sense to check the performance by increasing CLOG buffers (patch for same is posted in Speed up Clog thread [1]) as that also relieves contention on CLOG as per the tests I have done?
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