linux-ext4 - Re: [PATCH] resolve duplicate flag no for PG

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Message-Id: <20070514134606.695f087a.akpm@linux-foundation.org>
Date:	Mon, 14 May 2007 13:46:06 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Theodore Tso <tytso@....edu>
Cc:	Fengguang Wu <fengguang.wu@...il.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Rik van Riel <riel@...hat.com>,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
	Nick Piggin <nickpiggin@...oo.com.au>
Subject: Re: [PATCH] resolve duplicate flag no for PG_lazyfree

On Mon, 14 May 2007 14:06:19 -0400
Theodore Tso <tytso@....edu> wrote:

> On Sun, May 13, 2007 at 10:46:30PM -0700, Andrew Morton wrote:
> > otoh, the intersection between pages which are PageBooked() and pages which
> > are PageLazyFree() should be zreo, so it'd be good to actually formalise
> > this reuse within the ext4 patches.
> > 
> > otoh2, PageLazyFree() could have reused PG_owner_priv_1.
> > 
> > Rik, Ted: any thoughts?  We do need to scrimp on page flags: when we
> > finally run out, we're screwed.
> 
> It makes sense to me.  PG_lazyfree is currently only in -mm, right?

Ah, yes, I got confused, sorry.

>  I
> don't see it in my git tree.  It would probably would be a good idea
> to make sure that we check to add some sanity checking code if it
> isn't there already that PG_lazyfree isn't already set when try to set
> PG_lazyfree (just in case there is a bug in the future which causes
> the should-never-happen case of trying lazy free a PageBooked page).
> 

Actually, I think the current status of
lazy-freeing-of-memory-through-madv_free.patch is "might not be needed".  I
_think_ we've determined that 0a27a14a62921b438bb6f33772690d345a089be6
sufficiently fixed the perfomance problems we had in there?
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