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Re: fopen from within a pthread
- From: Carlos O'Donell <carlos at redhat dot com>
- To: Paul Pluzhnikov <ppluzhnikov at google dot com>, mebeyn at gmail dot com
- Cc: libc-help at sourceware dot org
- Date: Mon, 4 Jun 2018 10:38:25 -0400
- Subject: Re: fopen from within a pthread
- References: <CADpW=+3ve0oLtby3gneBdiQekjUnqZ66yvhkPUV-LSD9Femail@example.com> <CALoOobPHVFYCGpoTmftYMYHvRe=7QTrz_MBY-QwJ04tTMDX4uQ@mail.gmail.com>
On 06/02/2018 06:48 PM, Paul Pluzhnikov via libc-help wrote:
> On Sat, Jun 2, 2018 at 3:31 PM Martin Beynon <firstname.lastname@example.org> wrote:
>> Is this erroneous behaviour, or can this be explained in some way?
> There is nothing erroneous about it.
> What you are observing is the creation of thread-specific arena, from
> which malloc will return memory to the new thread.
> GLIBC uses thread-specific arenas to avoid having to lock malloc
> internal structures when multiple threads allocate and free memory.
> Additional info can be found here:
Also note that VM size is not the same as RSS.
The new thread arena, usually ~64MiB in size on 64-bit, is only taking
up VM space, but not consuming any real memory (RSS).
Therefore this is just an accounting procedure. Real memory will only
be used as you dirty the pages.