From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932562AbbFEMFI (ORCPT ); Fri, 5 Jun 2015 08:05:08 -0400 Received: from mail-pd0-f178.google.com ([209.85.192.178]:36718 "EHLO mail-pd0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932238AbbFEMFE (ORCPT ); Fri, 5 Jun 2015 08:05:04 -0400 From: Sergey Senozhatsky To: Andrew Morton , Minchan Kim Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Sergey Senozhatsky , Sergey Senozhatsky Subject: [RFC][PATCHv2 5/8] zsmalloc: introduce zs_can_compact() function Date: Fri, 5 Jun 2015 21:03:55 +0900 Message-Id: <1433505838-23058-6-git-send-email-sergey.senozhatsky@gmail.com> X-Mailer: git-send-email 2.4.2.387.gf86f31a In-Reply-To: <1433505838-23058-1-git-send-email-sergey.senozhatsky@gmail.com> References: <1433505838-23058-1-git-send-email-sergey.senozhatsky@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This function checks if class compaction will free any pages. Rephrasing -- do we have enough unused objects to form at least one ZS_EMPTY page and free it. It aborts compaction if class compaction will not result in any (further) savings. EXAMPLE (this debug output is not part of this patch set): -- class size -- number of allocated objects -- number of used objects, -- estimated number of pages that will be freed [..] class-3072 objs:24652 inuse:24628 maxobjs-per-page:4 pages-tofree:6 class-3072 objs:24648 inuse:24628 maxobjs-per-page:4 pages-tofree:5 class-3072 objs:24644 inuse:24628 maxobjs-per-page:4 pages-tofree:4 class-3072 objs:24640 inuse:24628 maxobjs-per-page:4 pages-tofree:3 class-3072 objs:24636 inuse:24628 maxobjs-per-page:4 pages-tofree:2 class-3072 objs:24632 inuse:24628 maxobjs-per-page:4 pages-tofree:1 class-2720 objs:17970 inuse:17966 maxobjs-per-page:3 pages-tofree:1 class-2720 objs:17967 inuse:17966 maxobjs-per-page:3 pages-tofree:0 class-2720: Compaction is useless class-2448 objs:7680 inuse:7674 maxobjs-per-page:5 pages-tofree:1 class-2336 objs:13510 inuse:13500 maxobjs-per-page:7 pages-tofree:1 class-2336 objs:13503 inuse:13500 maxobjs-per-page:7 pages-tofree:0 class-2336: Compaction is useless class-1808 objs:1161 inuse:1154 maxobjs-per-page:9 pages-tofree:0 class-1808: Compaction is useless class-1744 objs:2135 inuse:2131 maxobjs-per-page:7 pages-tofree:0 class-1744: Compaction is useless class-1536 objs:1328 inuse:1323 maxobjs-per-page:8 pages-tofree:0 class-1536: Compaction is useless class-1488 objs:8855 inuse:8847 maxobjs-per-page:11 pages-tofree:0 class-1488: Compaction is useless class-1360 objs:14880 inuse:14878 maxobjs-per-page:3 pages-tofree:0 class-1360: Compaction is useless class-1248 objs:3588 inuse:3577 maxobjs-per-page:13 pages-tofree:0 class-1248: Compaction is useless class-1216 objs:3380 inuse:3372 maxobjs-per-page:10 pages-tofree:0 class-1216: Compaction is useless class-1168 objs:3416 inuse:3401 maxobjs-per-page:7 pages-tofree:2 class-1168 objs:3409 inuse:3401 maxobjs-per-page:7 pages-tofree:1 class-1104 objs:605 inuse:599 maxobjs-per-page:11 pages-tofree:0 class-1104: Compaction is useless [..] Every "Compaction is useless" indicates that we saved some CPU cycles. class-1104 has 605 object allocated 599 objects used 11 objects per-page Even if we have a ALMOST_EMPTY zspage, we still don't have enough room to migrate all of its objects and free this zspage; so compaction will not make a lot of sense here, it's better to just leave it as is. Signed-off-by: Sergey Senozhatsky --- mm/zsmalloc.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c index 0453347..5d8f1d4 100644 --- a/mm/zsmalloc.c +++ b/mm/zsmalloc.c @@ -1682,6 +1682,28 @@ static struct page *isolate_source_page(struct size_class *class) return page; } +/* + * Make sure that we actually can compact this class, + * IOW if migration will empty at least one page. + * + * Should be called under class->lock + */ +static unsigned long zs_can_compact(struct size_class *class) +{ + /* + * Calculate how many unused allocated objects we + * have and see if we can free any zspages. Otherwise, + * compaction can just move objects back and forth w/o + * any memory gain. + */ + unsigned long obj_wasted = zs_stat_get(class, OBJ_ALLOCATED) - + zs_stat_get(class, OBJ_USED); + + obj_wasted /= get_maxobj_per_zspage(class->size, + class->pages_per_zspage); + return obj_wasted; +} + static unsigned long __zs_compact(struct zs_pool *pool, struct size_class *class) { @@ -1695,6 +1717,9 @@ static unsigned long __zs_compact(struct zs_pool *pool, BUG_ON(!is_first_page(src_page)); + if (!zs_can_compact(class)) + break; + cc.index = 0; cc.s_page = src_page; -- 2.4.2.387.gf86f31a From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f181.google.com (mail-pd0-f181.google.com [209.85.192.181]) by kanga.kvack.org (Postfix) with ESMTP id 11BCD900016 for ; Fri, 5 Jun 2015 08:05:05 -0400 (EDT) Received: by pdjn11 with SMTP id n11so14452358pdj.0 for ; Fri, 05 Jun 2015 05:05:04 -0700 (PDT) Received: from mail-pa0-x234.google.com (mail-pa0-x234.google.com. [2607:f8b0:400e:c03::234]) by mx.google.com with ESMTPS id ey4si10630819pdb.172.2015.06.05.05.05.04 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 05 Jun 2015 05:05:04 -0700 (PDT) Received: by pabqy3 with SMTP id qy3so49376578pab.3 for ; Fri, 05 Jun 2015 05:05:04 -0700 (PDT) From: Sergey Senozhatsky Subject: [RFC][PATCHv2 5/8] zsmalloc: introduce zs_can_compact() function Date: Fri, 5 Jun 2015 21:03:55 +0900 Message-Id: <1433505838-23058-6-git-send-email-sergey.senozhatsky@gmail.com> In-Reply-To: <1433505838-23058-1-git-send-email-sergey.senozhatsky@gmail.com> References: <1433505838-23058-1-git-send-email-sergey.senozhatsky@gmail.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton , Minchan Kim Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Sergey Senozhatsky , Sergey Senozhatsky This function checks if class compaction will free any pages. Rephrasing -- do we have enough unused objects to form at least one ZS_EMPTY page and free it. It aborts compaction if class compaction will not result in any (further) savings. EXAMPLE (this debug output is not part of this patch set): -- class size -- number of allocated objects -- number of used objects, -- estimated number of pages that will be freed [..] class-3072 objs:24652 inuse:24628 maxobjs-per-page:4 pages-tofree:6 class-3072 objs:24648 inuse:24628 maxobjs-per-page:4 pages-tofree:5 class-3072 objs:24644 inuse:24628 maxobjs-per-page:4 pages-tofree:4 class-3072 objs:24640 inuse:24628 maxobjs-per-page:4 pages-tofree:3 class-3072 objs:24636 inuse:24628 maxobjs-per-page:4 pages-tofree:2 class-3072 objs:24632 inuse:24628 maxobjs-per-page:4 pages-tofree:1 class-2720 objs:17970 inuse:17966 maxobjs-per-page:3 pages-tofree:1 class-2720 objs:17967 inuse:17966 maxobjs-per-page:3 pages-tofree:0 class-2720: Compaction is useless class-2448 objs:7680 inuse:7674 maxobjs-per-page:5 pages-tofree:1 class-2336 objs:13510 inuse:13500 maxobjs-per-page:7 pages-tofree:1 class-2336 objs:13503 inuse:13500 maxobjs-per-page:7 pages-tofree:0 class-2336: Compaction is useless class-1808 objs:1161 inuse:1154 maxobjs-per-page:9 pages-tofree:0 class-1808: Compaction is useless class-1744 objs:2135 inuse:2131 maxobjs-per-page:7 pages-tofree:0 class-1744: Compaction is useless class-1536 objs:1328 inuse:1323 maxobjs-per-page:8 pages-tofree:0 class-1536: Compaction is useless class-1488 objs:8855 inuse:8847 maxobjs-per-page:11 pages-tofree:0 class-1488: Compaction is useless class-1360 objs:14880 inuse:14878 maxobjs-per-page:3 pages-tofree:0 class-1360: Compaction is useless class-1248 objs:3588 inuse:3577 maxobjs-per-page:13 pages-tofree:0 class-1248: Compaction is useless class-1216 objs:3380 inuse:3372 maxobjs-per-page:10 pages-tofree:0 class-1216: Compaction is useless class-1168 objs:3416 inuse:3401 maxobjs-per-page:7 pages-tofree:2 class-1168 objs:3409 inuse:3401 maxobjs-per-page:7 pages-tofree:1 class-1104 objs:605 inuse:599 maxobjs-per-page:11 pages-tofree:0 class-1104: Compaction is useless [..] Every "Compaction is useless" indicates that we saved some CPU cycles. class-1104 has 605 object allocated 599 objects used 11 objects per-page Even if we have a ALMOST_EMPTY zspage, we still don't have enough room to migrate all of its objects and free this zspage; so compaction will not make a lot of sense here, it's better to just leave it as is. Signed-off-by: Sergey Senozhatsky --- mm/zsmalloc.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c index 0453347..5d8f1d4 100644 --- a/mm/zsmalloc.c +++ b/mm/zsmalloc.c @@ -1682,6 +1682,28 @@ static struct page *isolate_source_page(struct size_class *class) return page; } +/* + * Make sure that we actually can compact this class, + * IOW if migration will empty at least one page. + * + * Should be called under class->lock + */ +static unsigned long zs_can_compact(struct size_class *class) +{ + /* + * Calculate how many unused allocated objects we + * have and see if we can free any zspages. Otherwise, + * compaction can just move objects back and forth w/o + * any memory gain. + */ + unsigned long obj_wasted = zs_stat_get(class, OBJ_ALLOCATED) - + zs_stat_get(class, OBJ_USED); + + obj_wasted /= get_maxobj_per_zspage(class->size, + class->pages_per_zspage); + return obj_wasted; +} + static unsigned long __zs_compact(struct zs_pool *pool, struct size_class *class) { @@ -1695,6 +1717,9 @@ static unsigned long __zs_compact(struct zs_pool *pool, BUG_ON(!is_first_page(src_page)); + if (!zs_can_compact(class)) + break; + cc.index = 0; cc.s_page = src_page; -- 2.4.2.387.gf86f31a -- 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