Re: SlabCheck leaks memory into TopMemoryContext

From: Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Andres Freund <andres(at)anarazel(dot)de>, Tomas Vondra <tv(at)fuzzy(dot)cz>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: SlabCheck leaks memory into TopMemoryContext
Date: 2020-01-16 16:25:00
Message-ID: 20200116162500.pcgxmykirm677mt6@development
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On Thu, Jan 16, 2020 at 10:27:01AM -0500, Tom Lane wrote:
>Andres Freund <andres(at)anarazel(dot)de> writes:
>> ... I thought you were asking whether
>> any additional memory could just be avoided...
>Well, I was kind of wondering that, but if it's not practical then
>preallocating the space instead will do.

I don't think it's practical to rework the checks in a way that would
not require allocations. Maybe it's possible, but I think it's not worth
the extra complexity.

The attached fix should do the trick - it pre-allocates the space when
creating the context. There is a bit of complexity because we want to
allocate the space as part of the context header, but nothin too bad. We
might optimize it a bit by using a regular bitmap (instead of just an
array of bools), but I haven't done that.


Tomas Vondra
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

Attachment Content-Type Size
slab-leak-fix.patch text/plain 3.0 KB

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