From: | Jim Nasby <Jim(dot)Nasby(at)BlueTreble(dot)com> |
---|---|
To: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> |
Cc: | Stephen Frost <sfrost(at)snowman(dot)net>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Petr Jelinek <petr(dot)jelinek(at)2ndquadrant(dot)com>, Magnus Hagander <magnus(at)hagander(dot)net>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Checksums by default? |
Date: | 2017-01-24 00:36:25 |
Message-ID: | 35190d2b-04aa-71df-de10-5dbe6cd9b33e@BlueTreble.com |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
On 1/23/17 1:30 AM, Amit Kapila wrote:
> On Sun, Jan 22, 2017 at 3:43 PM, Tomas Vondra
> <tomas(dot)vondra(at)2ndquadrant(dot)com> wrote:
>>
>> That being said, I'm ready to do some benchmarking on this, so that we have
>> at least some numbers to argue about. Can we agree on a set of workloads
>> that we want to benchmark in the first round?
>>
>
> I think if we can get data for pgbench read-write workload when data
> doesn't fit in shared buffers but fit in RAM, that can give us some
> indication. We can try by varying the ratio of shared buffers w.r.t
> data. This should exercise the checksum code both when buffers are
> evicted and at next read. I think it also makes sense to check the
> WAL data size for each of those runs.
I tried testing this (and thought I sent an email about it but don't see
it now :/). Unfortunately, on my laptop I wasn't getting terribly
consistent runs; I was seeing +/- ~8% TPS. Sometimes checksumps appeared
to add ~10% overhead, but it was hard to tell.
If someone has a more stable (is in, dedicated) setup, testing would be
useful.
BTW, I ran the test with small (default 128MB) shared_buffers, scale 50
(800MB database), sync_commit = off, checkpoint_timeout = 1min, to try
and significantly increase the rate of buffers being written out.
--
Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
Experts in Analytics, Data Architecture and PostgreSQL
Data in Trouble? Get it in Treble! http://BlueTreble.com
855-TREBLE2 (855-873-2532)
From | Date | Subject | |
---|---|---|---|
Next Message | Jim Nasby | 2017-01-24 00:39:29 | Re: Checksums by default? |
Previous Message | Merlin Moncure | 2017-01-24 00:20:56 | Re: Checksums by default? |