linux-kernel - Re: [patch 17/20] non-reclaimable mlocked pages

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Message-Id: <200712201034.22668.nickpiggin@yahoo.com.au>
Date:	Thu, 20 Dec 2007 10:34:22 +1100
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Rik van Riel <riel@...hat.com>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Lee Schermerhorn <lee.schermerhorn@...com>
Subject: Re: [patch 17/20] non-reclaimable mlocked pages

On Thursday 20 December 2007 00:45, Rik van Riel wrote:
> On Wed, 19 Dec 2007 11:56:48 +1100
>
> Nick Piggin <nickpiggin@...oo.com.au> wrote:
> > On Wednesday 19 December 2007 08:15, Rik van Riel wrote:
> > > Rework of a patch by Nick Piggin -- part 1 of 2.
> > >
> > > This patch:
> > >
> > > 1) defines the [CONFIG_]NORECLAIM_MLOCK sub-option and the
> > >    stub version of the mlock/noreclaim APIs when it's
> > >    not configured.  Depends on [CONFIG_]NORECLAIM.
> >
> > Hmm, I still don't know (or forgot) why you don't just use the
> > old scheme of having an mlock count in the LRU bit, and removing
> > the mlocked page from the LRU completely.
>
> How do we detect those pages reliably in the lumpy reclaim code?

They will have PG_mlocked set.


> > These mlocked pages don't need to be on a non-reclaimable list,
> > because we can find them again via the ptes when they become
> > unlocked, and there is no point background scanning them, because
> > they're always going to be locked while they're mlocked.
>
> Agreed.
>
> The main reason I sent out these patches now is that I just
> wanted to get some comments from other upstream developers.
>
> I have gotten distracted by other work so much that I spent
> most of my time forward porting the patch set, and not enough
> time working with the rest of the upstream community to get
> the code moving forward.
>
> To be honest, I have only briefly looked at the non-reclaimable
> code.  I would be more than happy to merge any improvements to
> that code.

I haven't had too much time to look at it either, although it does
seem like a reasonable idea.

However the mlock code could be completely separate from the slow
scan pages (and not be on those LRUs at all).
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