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From: ebiederm@xmission.com (Eric W. Biederman)
To: Nadia Derbey <Nadia.Derbey@bull.net>
Cc: Andrew Morton <akpm@osdl.org>, linux-kernel@vger.kernel.org
Subject: Re: [RFC][PATCH 6/6] automatic tuning applied to some kernel components
Date: Wed, 07 Feb 2007 14:18:57 -0700	[thread overview]
Message-ID: <m1mz3poeda.fsf@ebiederm.dsl.xmission.com> (raw)
In-Reply-To: <45B61E50.6020607@bull.net> (Nadia Derbey's message of "Tue, 23 Jan 2007 15:40:16 +0100")

Nadia Derbey <Nadia.Derbey@bull.net> writes:

>
> 2) why autotuning:
> There are at least 3 cases where it can be useful
> . for workloads that are known to need a big amount of a given resource type
> (say shared memories), but we don't know what the maximum amount needed will be
> . to solve the case of multiple applications running on a single system, and
> that need the same tunable to be adjusted to feet their needs
> . to make a system correctly react to eventual peak loads for a given resource
> usage, i.e. make it tune up *and down* as needed.

>
> In all these cases, the akt framework will enable the kernel to adapt to
> increasing / decreasing resource consumption:
> 1) avoid allocating "a priori" a big amount of memory that will be used only in
> extreme cases. This is the effect of doing an "echo <huge_value>
>> /proc/sys/kernel/shmmni"
>
> 2) the system will come back to the default values as soon as the peak load is
> over.

At least the ipc ones are supposed to be DOS limits not behavior
modifiers.  I do admit from looking at the code that there are some
consequences of increasing things like shmmni.  However I think we
would be better off with  better data structures and implementations
that remove these consequences than this autotuning of
denial-of-service limits.

i.e. I think you are treating the symptom not the problem.

Does this make sense?

Eric


  reply	other threads:[~2007-02-07 21:19 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 [this message]
2007-02-09 12:27         ` Nadia Derbey
2007-02-09 18:35           ` Eric W. Biederman
2007-02-13  9:06             ` Nadia Derbey
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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