linux-kernel - Re: [PATCH 0/13] Parallel struct page initialisation v4

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Message-ID: <20150506071246.GF2462@suse.de>
Date:	Wed, 6 May 2015 08:12:46 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Waiman Long <waiman.long@...com>, Nathan Zimmer <nzimmer@....com>,
	Dave Hansen <dave.hansen@...el.com>,
	Scott Norton <scott.norton@...com>,
	Daniel J Blueman <daniel@...ascale.com>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/13] Parallel struct page initialisation v4

On Tue, May 05, 2015 at 03:25:49PM -0700, Andrew Morton wrote:
> On Tue, 5 May 2015 23:13:29 +0100 Mel Gorman <mgorman@...e.de> wrote:
> 
> > > Alternatively, the page allocator can go off and synchronously
> > > initialize some pageframes itself.  Keep doing that until the
> > > allocation attempt succeeds.
> > > 
> > 
> > That was rejected during review of earlier attempts at this feature on
> > the grounds that it impacted allocator fast paths. 
> 
> eh?  Changes are only needed on the allocation-attempt-failed path,
> which is slow-path.

We'd have to distinguish between falling back to other zones because the
high zone is artifically exhausted and normal ALLOC_BATCH exhaustion. We'd
also have to avoid falling back to remote nodes prematurely. While I have
not tried an implementation, I expected they would need to be in the fast
paths unless I used jump labels to get around it. I'm going to try altering
when we initialise instead so that it happens earlier.

-- 
Mel Gorman
SUSE Labs
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