linux-kernel - Re: [PATCH 0/3] ipc: Further updates to sysv/mqueue limits

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Date:	Sat, 31 May 2014 07:20:50 +0200
From:	"Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
To:	Manfred Spraul <manfred@...orfullife.com>,
	Davidlohr Bueso <davidlohr.bueso@...com>,
	Rafael Aquini <aquini@...hat.com>,
	Rik van Riel <riel@...hat.com>
CC:	mtk.manpages@...il.com, LKML <linux-kernel@...r.kernel.org>,
	1vier1@....de
Subject: Re: [PATCH 0/3] ipc: Further updates to sysv/mqueue limits

On 05/29/2014 08:46 PM, Manfred Spraul wrote:
> Hi all,
> 
> a) If we increase SHMMAX/SHMALL, then it makes sense to
>    increase MSGMNI, too.
>    And: This allows to remove the automatic scaling (~300 lines)
> 
> b) We can also increase SEMMSL, SEMMNI and SEMOPM
> 
> c) I think it would make more sense if a namespace starts with the
>    limits from it's parent:
>    If an admin set the limits, then he probably wants that these limits also
>    apply for a new child namespace.

Hi Manfred,

This these patches change the API/ABI, could you CC linux-api [1] for future
iterations.

Cheers,

Michael

[1] https://www.kernel.org/doc/man-pages/linux-api-ml.html


> All patches are RFC - they compile, but that's it.
> 
> TODO:
> - check if the sysv sem limits are sane.
>   Especially the SEMOPM - if real users exist that pass > 1k ops, then
>   switch from kmalloc to vmalloc.
> 
>   @the Redhat developers: Do you have any idea where this "often
>   recommended" comes from?
>   https://access.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_Linux/5/html/Tuning_and_Optimizing_Red_Hat_Enterprise_Linux_for_Oracle_9i_and_10g_Databases/sect-Oracle_9i_and_10g_Tuning_Guide-Setting_Semaphores-The_SEMOPM_Parameter.html
> 
> - copy Davidlohrs explanation for the sysv shm limits to sysv msg and
>   sysv sem.
> 
> - check if we should also increase the limits for posix mqueue
> 
> - decide if it would make sense to increase IPCMNI:
> 
>   Right now, it is 32768. This means that after 65536 pairs of
>   semget()/semctl(IPC_RMID), semget() will return the same identifier
>   again - and a semop(old_id) won't return -EINVAL, instead it will
>   access the "new" array, which is probably now what the caller
>   intended to do.
> 
>   The split is arbitrary - we could also split it 1048576/2048 or any
>   other split we want.
> 
> - test everything.
> 
> --
> 	Manfred
> 


-- 
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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