* shmget.2: SHMALL & kernel version inconsistency ?
@ 2014-04-27 22:09 Simon Paillard
[not found] ` <20140427220916.GP18563-xazfMhTT2R0@public.gmane.org>
0 siblings, 1 reply; 2+ messages in thread
From: Simon Paillard @ 2014-04-27 22:09 UTC (permalink / raw)
To: linux-man-u79uwXL29TY76Z2rM5mHXA
Hi,
From shmget.2:
=======================================================================
SHMALL System wide maximum of shared memory pages. Since Linux 2.2,
the default value for this limit is
SHMMAX / PAGE_SIZE * (SHMMNI / 16)
Assuming a 4kB page size, this formula yields (since Linux 2.4)
the value 2^20 (2,097,152).
On Linux, this limit can be read and modified via /proc/sys/ker‐
nel/shmall.
=======================================================================
Linux 2.2 or 2.4 ?
I understand from lxr contant this is actually 2.4.
http://lxr.linux.no/#linux-old+v2.2.0/include/linux/shm.h#L53
http://lxr.linux.no/#linux-old+v2.4.0/include/linux/shm.h#L15
--
Simon Paillard
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* Re: shmget.2: SHMALL & kernel version inconsistency ?
[not found] ` <20140427220916.GP18563-xazfMhTT2R0@public.gmane.org>
@ 2014-04-28 7:39 ` Michael Kerrisk (man-pages)
0 siblings, 0 replies; 2+ messages in thread
From: Michael Kerrisk (man-pages) @ 2014-04-28 7:39 UTC (permalink / raw)
To: Simon Paillard, linux-man-u79uwXL29TY76Z2rM5mHXA
Cc: mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w
On 04/28/2014 12:09 AM, Simon Paillard wrote:
> Hi,
>
>>From shmget.2:
> =======================================================================
> SHMALL System wide maximum of shared memory pages. Since Linux 2.2,
> the default value for this limit is
>
> SHMMAX / PAGE_SIZE * (SHMMNI / 16)
>
> Assuming a 4kB page size, this formula yields (since Linux 2.4)
> the value 2^20 (2,097,152).
>
> On Linux, this limit can be read and modified via /proc/sys/ker‐
> nel/shmall.
> =======================================================================
>
> Linux 2.2 or 2.4 ?
>
> I understand from lxr contant this is actually 2.4.
> http://lxr.linux.no/#linux-old+v2.2.0/include/linux/shm.h#L53
> http://lxr.linux.no/#linux-old+v2.4.0/include/linux/shm.h#L15
Thanks, Simon. Yes, it should have been 2.4. The fix is in Git.
Cheers,
Michael
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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2014-04-27 22:09 shmget.2: SHMALL & kernel version inconsistency ? Simon Paillard
[not found] ` <20140427220916.GP18563-xazfMhTT2R0@public.gmane.org>
2014-04-28 7:39 ` Michael Kerrisk (man-pages)
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