linux-kernel - Re: [PATCH] add some drop_caches documentation and info messsge

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Message-Id: <20121024141303.0797d6a1.akpm@linux-foundation.org>
Date:	Wed, 24 Oct 2012 14:13:03 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Dave Hansen <dave@...ux.vnet.ibm.com>,
	Michal Hocko <mhocko@...e.cz>, linux-mm@...ck.org,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: [PATCH] add some drop_caches documentation and info messsge

On Wed, 24 Oct 2012 23:06:00 +0200
Borislav Petkov <bp@...en8.de> wrote:

> On Wed, Oct 24, 2012 at 01:48:36PM -0700, Andrew Morton wrote:
> > Well who knows. Could be that people's vm *does* suck. Or they have
> > some particularly peculiar worklosd or requirement[*]. Or their VM
> > *used* to suck, and the drop_caches is not really needed any more but
> > it's there in vendor-provided code and they can't practically prevent
> > it.
> 
> I have drop_caches in my suspend-to-disk script so that the hibernation
> image is kept at minimum and suspend times are as small as possible.

hm, that sounds smart.

> Would that be a valid use-case?

I'd say so, unless we change the kernel to do that internally.  We do
have the hibernation-specific shrink_all_memory() in the vmscan code. 
We didn't see fit to document _why_ that exists, but IIRC it's there to
create enough free memory for hibernation to be able to successfully
complete, but no more.

Who owns hibernaton nowadays?  Rafael, I guess?
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