linux-kernel - Re: [RFC PATCH 1/3] mm: teach mm by current context info to not do I/O during memory allocation

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Message-ID: <CACVXFVOdohPprD7N69=Tz2keTbLG7b-s5324OUX-oY84Jszumg@mail.gmail.com>
Date:	Tue, 16 Oct 2012 15:08:41 +0800
From:	Ming Lei <ming.lei@...onical.com>
To:	Minchan Kim <minchan@...nel.org>
Cc:	linux-kernel@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-usb@...r.kernel.org, linux-pm@...r.kernel.org,
	Alan Stern <stern@...land.harvard.edu>,
	Oliver Neukum <oneukum@...e.de>,
	Jiri Kosina <jiri.kosina@...e.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mel@....ul.ie>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Michal Hocko <mhocko@...e.cz>, Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, linux-mm <linux-mm@...ck.org>
Subject: Re: [RFC PATCH 1/3] mm: teach mm by current context info to not do
 I/O during memory allocation

On Tue, Oct 16, 2012 at 1:49 PM, Minchan Kim <minchan@...nel.org> wrote:
>
> Fair enough but it wouldn't be a good idea that add new unlikely branch
> in allocator's fast path. Please move the check into slow path which could
> be in __alloc_pages_slowpath.

Thanks for your comment.

I have considered to add the branch into gfp_to_alloc_flags() before,
but didn't do it because I see that get_page_from_freelist() may use
the GFP_IO or GFP_FS flag at least in zone_reclaim() path.

So could you make sure it is safe to move the branch into
__alloc_pages_slowpath()?  If so, I will add the check into
gfp_to_alloc_flags().


Thanks,
--
Ming Lei
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