CpuAffinityMask

[Tim Crawford]

I remember looking into this some time ago,
and not finding what I thought was reliable information.

Can someone point me to a good documentation/resources
regarding the CpuAffinityMask, specifically for 2.5
but also > 2.5 if things have changed

Thanks

[Karol Bieniaszewski]

This settings work nonly for superserver if i remember corectly.

If you leave it commented in config then Firebird will usee all available cores.

For FB3 it is ok, for FB2.5 FB should use max one CPU.

 

CpuAffinityMask as a name tell is simple bit mask. Numer of bits set to 1 then this core is used by FB.

 

Regards,

Karol Bieniaszewski

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[Tim Crawford]

Thanks for taking the time to reply, but I was looking for
a link to some documentation or something official.

For 2.5 Windows default is single CPU but it can be set, but
after reviewing my notes on this the last time I looked at it
I realized this is only of any value if you are running multiple
database on the server, a single database runs on one CPU only.

I prefer to use multiple FB instances for multiple production databases
anyway so I bring then down/up separately, and they run end up running
on separate CPUs anyway I think

To view this discussion on the web, visit https://groups.google.com/d/msgid/firebird-support/4Hm8tb3cwCzlgB8k%40smtp.poczta.onet.pl.

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[Mark Rotteveel]

On 05-11-2021 23:26, Tim Crawford wrote:
> Thanks for taking the time to reply, but I was looking for
> a link to some documentation or something official.

Most of the documentation is in the (default) firebird.conf itself.

> For 2.5 Windows default is single CPU but it can be set, but
> after reviewing my notes on this the last time I looked at it
> I realized this is only of any value if you are running multiple
> database on the server, a single database runs on one CPU only.
>
> I prefer to use multiple FB instances for multiple production databases
> anyway so I bring then down/up separately, and they run end up running
> on separate CPUs anyway I think

Not if they all have the same CpuAffinityMask. In any case, if you want
to bring individual databases down, you can also do that with a single
engine, by shutting down the database and bring it back online (e.g.
using gfix).

In any case, for Firebird 2.5, it is actually more complicated than what
Karol described, see the Firebird 2.5 release notes, section New
Threading Architecture[1]

"""
In a multiple database environment, Superserver threads for each
database are allotted evenly to available processors.

Note

The default CpuAffinity setting still binds SuperServer to a single
processor only. In order to take advantage of this improvement when
working with multiple databases, this setting should be changed in
firebird.conf.
"""

In other words, for the SuperServer model, each database has a thread,
and the threads are scheduled on the processor cores specified in the
CpuAffinityMask setting.

In Firebird 2.5, the default setting schedules on the first core, in
Firebird 3.0, the default setting schedules on all cores.

[1]:
https://www.firebirdsql.org/file/documentation/release_notes/html/en/2_5/rnfb25-engine.html#rnfb25-engine-threading

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Mark Rotteveel