From: Jesper Pedersen <jesper.pedersen@redhat.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: pgsql-hackers@postgresql.org <pgsql-hackers@postgresql.org>
Subject: Re: Additional LWLOCK_STATS statistics
Date: Tue, 15 Sep 2015 15:30:02 -0400
Message-ID: <55F871BA.4060404@redhat.com> (raw)
In-Reply-To: <CA+TgmoYvgL7rA6jBzn60FUeHhb5TH2xu2m9JKPiXFqbZ5Dyi7w@mail.gmail.com>
References: <55F82AE1.3010407@redhat.com>
<CA+TgmoYvgL7rA6jBzn60FUeHhb5TH2xu2m9JKPiXFqbZ5Dyi7w@mail.gmail.com>
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On 09/15/2015 03:11 PM, Robert Haas wrote:
>> If there is an interest I'll add the patch to the next CommitFest.
>>
>> Thanks for considering, and any feedback is most welcomed.
>
> Seems neat, but I can't understand how to read the flame graphs.
>
X-axis is sort of "up in the air" with flame graphs -- similar call
stacks are grouped together, and here it is the queue size.
Y-axis is the lock queue size -- e.g. CLogControlLock is "max'ed" out,
since there is a queue size of 80 with the -c/-j 80 run.
The width of each column shows how the locks are "distributed" within
the report. Mouse over on the lock name gives the % of the entire
report, f.ex. CLogControlLock has 74% of spin delays. Note, that some of
the reports are filtered in order to eliminate "unnecessary" information
-- see README.
You would need to zoom into some of the information - left click - and
the reset the zoom afterwards.
I can change the reports if something is more helpful.
Flame graphs for CPU profiling are more common, like
https://dl.dropboxusercontent.com/u/99317937/postgresql/96S-20150808-r30t-17353.svg
Thanks for looking at the patch.
Best regards,
Jesper
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To: pgsql-hackers@postgresql.org
Cc: jesper.pedersen@redhat.com, robertmhaas@gmail.com
Subject: Re: Additional LWLOCK_STATS statistics
In-Reply-To: <55F871BA.4060404@redhat.com>
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