linux-kernel - Re: [RFC PATCH v1 1/3] mm: teach mm by current context info to not do I/O during memory allocation

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Date:	Wed, 17 Oct 2012 18:56:14 +0800
From:	Ming Lei <ming.lei@...onical.com>
To:	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	linux-kernel@...r.kernel.org,
	Alan Stern <stern@...land.harvard.edu>,
	Oliver Neukum <oneukum@...e.de>,
	Minchan Kim <minchan@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-usb@...r.kernel.org, linux-pm@...r.kernel.org,
	Jiri Kosina <jiri.kosina@...e.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mel@....ul.ie>, 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 v1 1/3] mm: teach mm by current context info to not do
 I/O during memory allocation

On Wed, Oct 17, 2012 at 1:14 PM, Kamezawa Hiroyuki
<kamezawa.hiroyu@...fujitsu.com> wrote:
>
> I think the idea is reasonable. I have a request.

Thanks for your comment.

>
> In current implemententation of vmscan.c, it seems sc.may_writepage, sc.may_swap
> are handled independent from gfp_mask.
>
> So, could you drop changes from this patch and handle these flags in another patch
> if these flags should be unset if ~GFP_IOFS ?

OK, I agree. In theory,  mm should make sure no I/O is involved if
memory allocation
users passes ~GFP_IOFS.

>
> I think try_to_free_page() path's sc.may_xxxx should be handled in the same way.

Yes, alloc_page_buffers() and dma_alloc_from_contiguous may drop into
the path, so gfp flag should be changed in try_to_free_page() too.


Thanks,
--
Ming Lei
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