From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754854Ab1G1Be7 (ORCPT ); Wed, 27 Jul 2011 21:34:59 -0400 Received: from mga01.intel.com ([192.55.52.88]:40445 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753473Ab1G1Bey (ORCPT ); Wed, 27 Jul 2011 21:34:54 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.67,279,1309762800"; d="scan'208";a="35321941" Subject: Re: [PATCH]vmscan: add block plug for page reclaim From: Shaohua Li To: Andrew Morton Cc: Jens Axboe , Minchan Kim , "mgorman@suse.de" , linux-mm , lkml In-Reply-To: <20110727181527.c4f6d806.akpm@linux-foundation.org> References: <1311130413.15392.326.camel@sli10-conroe> <1311142253.15392.361.camel@sli10-conroe> <1311144559.15392.366.camel@sli10-conroe> <4E287EC0.4030208@fusionio.com> <1311311695.15392.369.camel@sli10-conroe> <4E2B17A6.6080602@fusionio.com> <20110727164523.c2b1d569.akpm@linux-foundation.org> <1311815060.15392.375.camel@sli10-conroe> <20110727181527.c4f6d806.akpm@linux-foundation.org> Content-Type: text/plain; charset="UTF-8" Date: Thu, 28 Jul 2011 09:34:52 +0800 Message-ID: <1311816892.15392.379.camel@sli10-conroe> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2011-07-28 at 09:15 +0800, Andrew Morton wrote: > On Thu, 28 Jul 2011 09:04:20 +0800 Shaohua Li wrote: > > > > Using an additional 44 bytes of stack on that path is also > > > significant(ly bad). But we need to fix that problem anyway. One way > > > we could improve things in mm/vmscan.c is to move the blk_plug into > > > scan_control then get the scan_control off the stack in some manner. > > > That's easy for kswapd: allocate one scan_control per kswapd at > > > startup. Doing it for direct-reclaim would be a bit trickier... > > unfortunately, the direct-reclaim case is what cares about stack. > > > > BTW, the scan_control can be dieted. may_unmap/may_swap/may_writepage > > can be a bit. swappiness < 100, so can be a char. order <= 11, can be a > > char. should I do it to cut the size? > > All five will fit in a 32-bit word, at some expense in code size. oh, I missed the code size will increase, so it's not good then. > But I think first it would be better to work on a way of getting it all > off the stack, along with the blk_plug. > > Could be done with a per-cpu array and CPU pinning, but CPU pinning is > a bit expensive nowadays. Could put a scan_control* into the > tack_struct, but that's dopey. looks it should be per task, as reclaim could sleep. either putting it to task_struct or allocating it, both are not good. Thanks, Shaohua