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From: Nadia Derbey <>
To: "Eric W. Biederman" <>
Cc: Andrew Morton <>,
Subject: Re: [RFC][PATCH 6/6] automatic tuning applied to some kernel components
Date: Tue, 13 Feb 2007 10:06:21 +0100	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

Eric W. Biederman wrote:
> Nadia Derbey <> writes:
>>I do not fully agree with you:
>>It is true that some ipc tunables play the role of DoS limits.
>>But IMHO the *mni ones (semmni, msgmni, shmmni) are used by the ipc subsystem to
>>adapt its data structures sizes to what is being asked for through the tunable
>>value. I think this is how they manage to take into account a new tunable value
>>without a need for rebooting the system: reallocate some more memory on demand.
> Yes, they do.  However if you are constantly having to play with shmmni or
> the others that is the problem and the array should be replaced with
> a hash table or some form of radix tree, so it changes it's size to fit
> the need.  Once that is done, shmmni does become a simple DOS limit.
> So what I'm asking is please fix the problem at the source don't plaster over
> it.
>>Now, what the akt framework does, is that it takes advantage of this concept of
>>"on demand memory allocation" to replace a user (or a daemon) that would
>>periodically check its ipcs consumptions and manually adjust the ipcs tunables:
>>Doing this from the user space would imply a latency that makes it difficult to
>>react fast enough to resources running out.
> There may be some sense in this but you haven't found something that inherently
> needs tuning.  You have found something that has a poor data structure,
> and can more easily be fixed by simply fixing the data structure.

So, should I understand from this that automatic tuning and the AKT 
framework itself would make sense, given that I find the rigth tunables 
it should be applied to?
Actually, dont' know if you had the opportunity to read all the patches, 
but there are 2 other tunables AKT is proposed to be applied to:
. max_threads, the tunable limit on nr_threads
. max_files, the tunable limit on nr_files


  reply	other threads:[~2007-02-13  9:03 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-01-16  6:15 [RFC][PATCH 0/6] Automatice kernel tunables (AKT) Nadia.Derbey
2007-01-16  6:15 ` [RFC][PATCH 1/6] Tunable structure and registration routines Nadia.Derbey
2007-01-25  0:32   ` Randy Dunlap
2007-01-25 16:26     ` Nadia Derbey
2007-01-25 16:34       ` Randy Dunlap
2007-01-25 17:01         ` Nadia Derbey
2007-01-16  6:15 ` [RFC][PATCH 2/6] auto_tuning activation Nadia.Derbey
2007-01-16  6:15 ` [RFC][PATCH 3/6] tunables associated kobjects Nadia.Derbey
2007-01-16  6:15 ` [RFC][PATCH 4/6] min and max kobjects Nadia.Derbey
2007-01-24 22:41   ` Randy Dunlap
2007-01-25 16:34     ` Nadia Derbey
2007-01-16  6:15 ` [RFC][PATCH 5/6] per namespace tunables Nadia.Derbey
2007-01-24 22:41   ` Randy Dunlap
2007-01-16  6:15 ` [RFC][PATCH 6/6] automatic tuning applied to some kernel components Nadia.Derbey
2007-01-22 19:56   ` Andrew Morton
2007-01-23 14:40     ` Nadia Derbey
2007-02-07 21:18       ` Eric W. Biederman
2007-02-09 12:27         ` Nadia Derbey
2007-02-09 18:35           ` Eric W. Biederman
2007-02-13  9:06             ` Nadia Derbey [this message]
2007-02-13 10:10               ` Eric W. Biederman
2007-02-15  7:07                 ` Nadia Derbey
2007-02-15  7:49                   ` Eric W. Biederman
2007-02-15  8:25                     ` Nadia Derbey
2007-02-14 13:56 Al Boldi

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