Re: Supporting huge pages on Windows

On Wed, Sep 28, 2016 at 1:26 PM, Tsunakawa, Takayuki
<tsunakawa(dot)takay(at)jp(dot)fujitsu(dot)com> wrote:
>> From: pgsql-hackers-owner(at)postgresql(dot)org
>> [mailto:pgsql-hackers-owner(at)postgresql(dot)org] On Behalf Of Robert Haas
>> On Sun, Sep 25, 2016 at 10:45 PM, Tsunakawa, Takayuki
>> <tsunakawa(dot)takay(at)jp(dot)fujitsu(dot)com> wrote:
>> > Credit: This patch is based on Thomas Munro's one.
>>
>> How are they different?
>
> As Thomas mentioned, his patch (only win32_shmem.c) might not have been able to compile (though I didn't try.) And it didn't have error processing or documentation. I added error handling, documentation, comments, and a little bit of structural change. The possibly biggest change, though it's only one-liner in pg_ctl.c, is additionally required. I failed to include it in the first patch. The attached patch includes that.

Right, my patch[1] was untested sketch code. I had heard complaints
about poor performance with large shared_buffers on Windows, and then
I bumped into some recommendations to turn large pages on for a couple
of other RDBMSs if using large buffer pool. So I wrote that patch
based on the documentation to try some time in the future if I ever
got trapped in a room with Windows, but I posted it just in case the
topic would interest other hackers. Thanks for picking it up!

> huge_pages=off: 70412 tps
> huge_pages=on : 72100 tps

Hmm. I guess it could be noise or random code rearrangement effects.
I saw your recent post[2] proposing to remove the sentence about the
512MB effective limit and I wondered why you didn't go to larger sizes
with a larger database and more run time. But I will let others with
more benchmarking experience comment on the best approach to
investigate Windows shared_buffers performance.

[1] https://www.postgresql.org/message-id/CAEepm=075-bgHi_VDt4SCAmt+o_+1XaRap2zh7XwfZvT294oHA@mail.gmail.com
[2] https://www.postgresql.org/message-id/0A3221C70F24FB45833433255569204D1F5EE995@G01JPEXMBYT05

--
Thomas Munro
http://www.enterprisedb.com