[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <87y42jo5k1.fsf@tassilo.jf.intel.com>
Date: Thu, 22 Sep 2016 16:53:02 -0700
From: Andi Kleen <andi@...stfloor.org>
To: "Chen\, Tim C" <tim.c.chen@...el.com>
Cc: Shaohua Li <shli@...nel.org>,
"Huang\, Ying" <ying.huang@...el.com>,
Andrew Morton <akpm@...ux-foundation.org>,
"Hansen\, Dave" <dave.hansen@...el.com>,
"Kleen\, Andi" <andi.kleen@...el.com>,
"Lu\, Aaron" <aaron.lu@...el.com>,
"linux-mm\@kvack.org" <linux-mm@...ck.org>,
"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
Hugh Dickins <hughd@...gle.com>,
Minchan Kim <minchan@...nel.org>,
Rik van Riel <riel@...hat.com>,
Andrea Arcangeli <aarcange@...hat.com>,
"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
Vladimir Davydov <vdavydov@...tuozzo.com>,
Johannes Weiner <hannes@...xchg.org>,
Michal Hocko <mhocko@...nel.org>
Subject: Re: [PATCH -v3 00/10] THP swap: Delay splitting THP during swapping out
"Chen, Tim C" <tim.c.chen@...el.com> writes:
>>
>>So this is impossible without THP swapin. While 2M swapout makes a lot of
>>sense, I doubt 2M swapin is really useful. What kind of application is 'optimized'
>>to do sequential memory access?
Anything that touches regions larger than 4K and we want to do the
kernel do minimal work to manage the swapping.
>
> We waste a lot of cpu cycles to re-compact 4K pages back to a large page
> under THP. Swapping it back in as a single large page can avoid
> fragmentation and this overhead.
Also splitting something just to merge it again is wasteful.
A lot of big improvements in the block and VM and network layers
over the years came from avoiding that kind of wasteful work.
-Andi
Powered by blists - more mailing lists