From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl0-f70.google.com (mail-pl0-f70.google.com [209.85.160.70]) by kanga.kvack.org (Postfix) with ESMTP id 4CED46B0007 for ; Mon, 26 Feb 2018 22:16:10 -0500 (EST) Received: by mail-pl0-f70.google.com with SMTP id t2so8597745plr.15 for ; Mon, 26 Feb 2018 19:16:10 -0800 (PST) Received: from mga05.intel.com (mga05.intel.com. [192.55.52.43]) by mx.google.com with ESMTPS id u3si6371622pgr.447.2018.02.26.19.16.09 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 26 Feb 2018 19:16:09 -0800 (PST) Date: Tue, 27 Feb 2018 11:17:07 +0800 From: Aaron Lu Subject: Re: [PATCH v3 2/3] mm/free_pcppages_bulk: do not hold lock when picking pages to free Message-ID: <20180227031707.GB28977@intel.com> References: <20180226135346.7208-1-aaron.lu@intel.com> <20180226135346.7208-3-aaron.lu@intel.com> <20180227020058.GB9141@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180227020058.GB9141@intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: David Rientjes Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Huang Ying , Dave Hansen , Kemi Wang , Tim Chen , Andi Kleen , Michal Hocko , Vlastimil Babka , Mel Gorman , Matthew Wilcox On Tue, Feb 27, 2018 at 10:00:58AM +0800, Aaron Lu wrote: > On Mon, Feb 26, 2018 at 01:53:10PM -0800, David Rientjes wrote: > > On Mon, 26 Feb 2018, Aaron Lu wrote: > > > > > @@ -1144,26 +1142,31 @@ static void free_pcppages_bulk(struct zone *zone, int count, > > > batch_free = count; > > > > > > do { > > > - int mt; /* migratetype of the to-be-freed page */ > > > - > > > page = list_last_entry(list, struct page, lru); > > > /* must delete as __free_one_page list manipulates */ > > > > Looks good in general, but I'm not sure how I reconcile this comment with > > the new implementation that later links page->lru again. > > Thanks for pointing this out. > > I think the comment is useless now since there is a list_add_tail right > below so it's obvious we need to take the page off its original list. > I'll remove the comment in an update. Thinking again, I think I'll change the comment to: - /* must delete as __free_one_page list manipulates */ + /* must delete to avoid corrupting pcp list */ list_del(&page->lru); pcp->count--; Meanwhile, I'll add one more comment about why list_for_each_entry_safe is used: + /* + * Use safe version since after __free_one_page(), + * page->lru.next will not point to original list. + */ + list_for_each_entry_safe(page, tmp, &head, lru) { + int mt = get_pcppage_migratetype(page); + /* MIGRATE_ISOLATE page should not go to pcplists */ + VM_BUG_ON_PAGE(is_migrate_isolate(mt), page); + /* Pageblock could have been isolated meanwhile */ + if (unlikely(isolated_pageblocks)) + mt = get_pageblock_migratetype(page); + + __free_one_page(page, page_to_pfn(page), zone, 0, mt); + trace_mm_page_pcpu_drain(page, 0, mt); + } spin_unlock(&zone->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/ . Don't email: email@kvack.org