From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with ESMTP id C7F108D0039 for ; Mon, 28 Feb 2011 18:25:17 -0500 (EST) Received: by pwi10 with SMTP id 10so1173209pwi.14 for ; Mon, 28 Feb 2011 15:25:15 -0800 (PST) Date: Tue, 1 Mar 2011 08:25:08 +0900 From: Minchan Kim Subject: Re: [PATCH 2/2] mm: compaction: Minimise the time IRQs are disabled while isolating pages for migration Message-ID: <20110228232508.GA2265@barrios-desktop> References: <1298664299-10270-1-git-send-email-mel@csn.ul.ie> <1298664299-10270-3-git-send-email-mel@csn.ul.ie> <20110228230131.GB1896@barrios-desktop> <20110228230712.GR22700@random.random> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110228230712.GR22700@random.random> Sender: owner-linux-mm@kvack.org List-ID: To: Andrea Arcangeli Cc: Mel Gorman , Andrew Morton , Arthur Marsh , Clemens Ladisch , Linux-MM , Linux Kernel Mailing List On Tue, Mar 01, 2011 at 12:07:12AM +0100, Andrea Arcangeli wrote: > On Tue, Mar 01, 2011 at 08:01:31AM +0900, Minchan Kim wrote: > > I am not sure it's good if we release the lock whenever lru->lock was contended > > unconditionally? There are many kinds of lru_lock operations(add to lru, > > del from lru, isolation, reclaim, activation, deactivation and so on). > > This is mostly to mirror cond_resched_lock (which actually uses > spin_needbreak but it's ok to have it also when preempt is off). I > doubt it makes a big difference but I tried to mirror > cond_resched_lock. But what's the benefit of releasing lock in here when lock contentionn happen where activate_page for example? > > > Do we really need to release the lock whenever all such operations were contened? > > I think what we need is just spin_is_contended_irqcontext. > > Otherwise, please write down the comment for justifying for it. > > What is spin_is_contended_irqcontext? I thought what we need function is to check lock contention happened in only irq context for short irq latency. > > > This patch is for reducing for irq latency but do we have to check signal > > in irq hold time? > > I think it's good idea to check the signal in case the loop is very > long and this is run in direct compaction context. I don't oppose the signal check. I am not sure why we should check by just sign of lru_lock contention. How about this by coarse-grained? /* give a chance to irqs before checking need_resched() */ if (!((low_pfn+1) % SWAP_CLUSTER_MAX)) { if (fatal_signal_pending(current)) break; spin_unlock_irq(&zone->lru_lock); unlocked = true; } if (need_resched() || spin_is_contended(&zone->lru_lock)) { if (!unlocked) spin_unlock_irq(&zone->lru_lock); cond_resched(); spin_lock_irq(&zone->lru_lock); } else if (unlocked) spin_lock_irq(&zone->lru_lock); > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@kvack.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ > Don't email: email@kvack.org -- Kind regards, Minchan Kim -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org