[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <1347493482.9977.94.camel@schen9-DESK>
Date: Wed, 12 Sep 2012 16:44:42 -0700
From: Tim Chen <tim.c.chen@...ux.intel.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Mel Gorman <mel@....ul.ie>, Minchan Kim <minchan@...nel.org>,
Johannes Weiner <hannes@...xchg.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
Andrea Arcangeli <aarcange@...hat.com>,
David Rientjes <rientjes@...gle.com>,
Michal Hocko <mhocko@...e.cz>,
Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>,
Paul Gortmaker <paul.gortmaker@...driver.com>,
Matthew Wilcox <willy@...ux.intel.com>,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
Andi Kleen <ak@...ux.intel.com>, linux-mm@...ck.org,
linux-kernel <linux-kernel@...r.kernel.org>,
Alex Shi <alex.shi@...el.com>,
Fengguang Wu <fengguang.wu@...el.com>
Subject: Re: [PATCH 0/3 v2] mm: Batch page reclamation under shink_page_list
On Wed, 2012-09-12 at 12:27 -0700, Andrew Morton wrote:
>
> That sounds good, although more details on the performance changes
> would be appreciated - after all, that's the entire point of the
> patchset.
>
> And we shouldn't only test for improvements - we should also test for
> degradation. What workloads might be harmed by this change? I'd suggest
>
> - a single process which opens N files and reads one page from each
> one, then repeats. So there are no contiguous LRU pages which share
> the same ->mapping. Get some page reclaim happening, measure the
> impact.
>
> - The batching means that we now do multiple passes over pageframes
> where we used to do things in a single pass. Walking all those new
> page lists will be expensive if they are lengthy enough to cause L1
> cache evictions.
I need to address both your concerns and Mel's concerns about the
downside of prolonging the holding page locks for the pages to be
unmmaped for patch 1 in the series. I'll try to do some testing to see
what kind of benefit I get by only batching operations under the
i_mmap_mutex (i.e. patch 2 and 3 only) and not do batch unmap. Those
other changes don't have the downsides of prolonged page locking and we
can incorporate them with less risks.
>
> What would be a test for this? A simple, single-threaded walk
> through a file, I guess?
Thanks for your test suggestions. I will do tests along your
suggestions when I generate the next iterations of the patch.
I've been playing with these patches for a while and they are based on
3.4 kernel. I'll move them to 3.6 kernel in my next iteration.
>
> Mel's review comments were useful, thanks.
Very much appreciate comments from you, Mel and Minchan. I'll try to
incorporate them in my changes.
Tim
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists