From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Dave Wright <wrightd@gmail.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Should calculation of vm.overcommit_ratio be changed?
Date: Tue, 20 Apr 2010 18:32:52 +0100 [thread overview]
Message-ID: <20100420183252.0c61208f@lxorguk.ukuu.org.uk> (raw)
In-Reply-To: <y2kf16bc8301004200640r9485da73p920a2f5c3e2d949e@mail.gmail.com>
> might have 4GB RAM and 1GB swap. I don't think you would expect
> Desktop users to understand or tweak overcommit_ratio, but I also
> don't think having the distro simply change the default from 50 (to
> 100 or something else) would cover all the cases well.
Sounds like the distribution should be tuning the value according to the
>
> Would it make more sense to have the overcommit formula be calculated as:
>
> max commit = min(swap, ram) * overcommit_ratio + max(swap, ram) ?
>
> When swap>=ram, the formula works exactly the same as it does now, but
> when ram>>swap, you are guaranteed to always be able to your full RAM
> (even when swap=0).
Which is wromg - some of your RAM ends up eaten by the kernel, by
pagetables and buffers etc. 50% is probably very conservative but the
point of VM overcommit is exactly that - and you end up deploying swap
as a precaution against disaster rather than because you need it.
next prev parent reply other threads:[~2010-04-20 17:28 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-04-20 13:40 Dave Wright
2010-04-20 17:32 ` Alan Cox [this message]
2010-04-20 18:06 ` Dave Wright
2010-04-20 20:51 Dirk Geschke
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