From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx161.postini.com [74.125.245.161]) by kanga.kvack.org (Postfix) with SMTP id DED5F6B0062 for ; Wed, 19 Sep 2012 15:28:02 -0400 (EDT) Date: Wed, 19 Sep 2012 12:28:01 -0700 From: Andrew Morton Subject: Re: [PATCH v4 1/4] mm: fix tracing in free_pcppages_bulk() Message-Id: <20120919122801.ec1aa1df.akpm@linux-foundation.org> In-Reply-To: <1347632974-20465-2-git-send-email-b.zolnierkie@samsung.com> References: <1347632974-20465-1-git-send-email-b.zolnierkie@samsung.com> <1347632974-20465-2-git-send-email-b.zolnierkie@samsung.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Bartlomiej Zolnierkiewicz Cc: linux-mm@kvack.org, m.szyprowski@samsung.com, mina86@mina86.com, minchan@kernel.org, mgorman@suse.de, hughd@google.com, kyungmin.park@samsung.com On Fri, 14 Sep 2012 16:29:31 +0200 Bartlomiej Zolnierkiewicz wrote: > page->private gets re-used in __free_one_page() to store page order > (so trace_mm_page_pcpu_drain() may print order instead of migratetype) > thus migratetype value must be cached locally. > > Fixes regression introduced in a701623 ("mm: fix migratetype bug > which slowed swapping"). Grumble. Please describe a bug when fixing it! I've added here the text "This caused incorrect data to be attached to the mm_page_pcpu_drain trace event", which is hopefully correct enough. As it's been this way for 2.5 years, I assume that this can wait for 3.7. > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -668,12 +668,15 @@ static void free_pcppages_bulk(struct zone *zone, int count, > batch_free = to_free; > > do { > + int mt; > + > page = list_entry(list->prev, struct page, lru); > /* must delete as __free_one_page list manipulates */ > list_del(&page->lru); > + mt = page_private(page); > /* MIGRATE_MOVABLE list may include MIGRATE_RESERVEs */ > - __free_one_page(page, zone, 0, page_private(page)); > - trace_mm_page_pcpu_drain(page, 0, page_private(page)); > + __free_one_page(page, zone, 0, mt); > + trace_mm_page_pcpu_drain(page, 0, mt); > } while (--to_free && --batch_free && !list_empty(list)); > } > __mod_zone_page_state(zone, NR_FREE_PAGES, count); More grumble. Look: akpm:/usr/src/25> grep migratetype mm/page_alloc.c | wc -l 115 We should respect the established naming conventions. But reusing local var `maigratetype' here is not good practice, so how about --- a/mm/page_alloc.c~mm-fix-tracing-in-free_pcppages_bulk-fix +++ a/mm/page_alloc.c @@ -668,7 +668,7 @@ static void free_pcppages_bulk(struct zo batch_free = to_free; do { - int mt; + int mt; /* migratetype of the to-be-freed page */ page = list_entry(list->prev, struct page, lru); /* must delete as __free_one_page list manipulates */ _ -- 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