Re: Understanding Postgres Memory Usage - Mailing list pgsql-general

From Tom Lane
Subject Re: Understanding Postgres Memory Usage
Date
Msg-id 21142.1472153667@sss.pgh.pa.us
Whole thread Raw
In response to Re: Understanding Postgres Memory Usage  (Theron Luhn <theron@luhn.com>)
Responses Re: Understanding Postgres Memory Usage  (Theron Luhn <theron@luhn.com>)
List pgsql-general
Theron Luhn <theron@luhn.com> writes:
>> It would be worth using plain old top to watch this process.  We have
>> enough experience with that to be pretty sure how to interpret its
>> numbers: "RES minus SHR" is the value to be worried about.

> Sure thing.  https://gist.github.com/luhn/e09522d524354d96d297b153d1479c13#file-top-txt

> RES - SHR is showing a similar increase to what smem is reporting.

Hm, yeah, and the VIRT column agrees --- so 100MB of non-shared
memory went somewhere.  Seems like a lot.

If you have debug symbols installed for this build, you could try
doing

    gdb /path/to/postgres processID
    gdb> call MemoryContextStats(TopMemoryContext)
    gdb> quit

(when the process has reached an idle but bloated state) and seeing what
gets printed to the process's stderr.  (You need to have launched the
postmaster with its stderr directed to a file, not to /dev/null.)
That would provide a better clue about what's eating space.

            regards, tom lane


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