From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> To: Minchan Kim <minchan@kernel.org> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>, Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> Subject: Re: [RFC][PATCHv2 8/8] zsmalloc: register a shrinker to trigger auto-compaction Date: Wed, 17 Jun 2015 16:11:02 +0900 [thread overview] Message-ID: <20150617071102.GA3517@swordfish> (raw) In-Reply-To: <20150616144730.GD31387@blaptop> Hello, On (06/16/15 23:47), Minchan Kim wrote: [..] > > I like the idea but still have a concern to lack of fragmented zspages > during memory pressure because auto-compaction will prevent fragment > most of time. Surely, using fragment space as buffer in heavy memory > pressure is not intened design so it could be fragile but I'm afraid > this feature might accelrate it and it ends up having a problem and > change current behavior in zram as swap. > > I hope you test this feature with considering my concern. > Of course, I will test it with enough time. > OK, to explore "compaction leaves no fragmentation in classes" I did some heavy testing today -- parallel copy/remove of the linux kernel, git, glibc; parallel builds (-j4), parallel clean ups (make clean); git gc, etc. device's IO stats: cat /sys/block/zram0/stat← 277050 0 2216400 1463 8442846 0 67542768 106536 0 107810 108146 device's MM stats: cat /sys/block/zram0/mm_stat← 3095515136 2020518768 2057990144 0 2645716992 2030 182119 We auto-compacted (mostly auto-compacted, because I triggered manual compaction less than 5 times) 182119 objects. Now, during the compaction I also accounted the number of classes that ended up to be 'fully compacted' (class->OBJ_ALLOCATED) == class->OBJ_USED) and 'partially compacted'. And the results (after 1377 compactions) are: pool compaction nr:1377 (full:487 part:35498) So, we 'fully compact'-ed only 487/(35498 + 487) == 0.0135 roughtly ~1.35% This argument does not stand anymore. We leave 'holes' in classes in ~98% of the cases. code that I used to gather those stats: --- diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c index 55cfda8..894773a 100644 --- a/mm/zsmalloc.c +++ b/mm/zsmalloc.c @@ -253,6 +253,9 @@ struct zs_pool { #ifdef CONFIG_ZSMALLOC_STAT struct dentry *stat_dentry; #endif + int compaction_nr; + long full_compact; + long part_compact; }; /* @@ -1717,6 +1720,7 @@ static void __zs_compact(struct zs_pool *pool, struct size_class *class) struct zs_compact_control cc; struct page *src_page; struct page *dst_page = NULL; + bool compacted = false; spin_lock(&class->lock); while ((src_page = isolate_source_page(class))) { @@ -1726,6 +1730,8 @@ static void __zs_compact(struct zs_pool *pool, struct size_class *class) if (!zs_can_compact(class)) break; + compacted = true; + cc.index = 0; cc.s_page = src_page; @@ -1751,6 +1757,13 @@ out: if (src_page) putback_zspage(pool, class, src_page); + if (compacted) { + if (zs_stat_get(class, OBJ_ALLOCATED) == zs_stat_get(class, OBJ_USED)) + pool->full_compact++; + else + pool->part_compact++; + } + spin_unlock(&class->lock); } @@ -1767,6 +1780,11 @@ unsigned long zs_compact(struct zs_pool *pool) continue; __zs_compact(pool, class); } + + pool->compaction_nr++; + pr_err("pool compaction nr:%d (full:%ld part:%ld)\n", pool->compaction_nr, + pool->full_compact, pool->part_compact); + return pool->num_migrated; } EXPORT_SYMBOL_GPL(zs_compact);
WARNING: multiple messages have this Message-ID (diff)
From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> To: Minchan Kim <minchan@kernel.org> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>, Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> Subject: Re: [RFC][PATCHv2 8/8] zsmalloc: register a shrinker to trigger auto-compaction Date: Wed, 17 Jun 2015 16:11:02 +0900 [thread overview] Message-ID: <20150617071102.GA3517@swordfish> (raw) In-Reply-To: <20150616144730.GD31387@blaptop> Hello, On (06/16/15 23:47), Minchan Kim wrote: [..] > > I like the idea but still have a concern to lack of fragmented zspages > during memory pressure because auto-compaction will prevent fragment > most of time. Surely, using fragment space as buffer in heavy memory > pressure is not intened design so it could be fragile but I'm afraid > this feature might accelrate it and it ends up having a problem and > change current behavior in zram as swap. > > I hope you test this feature with considering my concern. > Of course, I will test it with enough time. > OK, to explore "compaction leaves no fragmentation in classes" I did some heavy testing today -- parallel copy/remove of the linux kernel, git, glibc; parallel builds (-j4), parallel clean ups (make clean); git gc, etc. device's IO stats: cat /sys/block/zram0/stata?? 277050 0 2216400 1463 8442846 0 67542768 106536 0 107810 108146 device's MM stats: cat /sys/block/zram0/mm_stata?? 3095515136 2020518768 2057990144 0 2645716992 2030 182119 We auto-compacted (mostly auto-compacted, because I triggered manual compaction less than 5 times) 182119 objects. Now, during the compaction I also accounted the number of classes that ended up to be 'fully compacted' (class->OBJ_ALLOCATED) == class->OBJ_USED) and 'partially compacted'. And the results (after 1377 compactions) are: pool compaction nr:1377 (full:487 part:35498) So, we 'fully compact'-ed only 487/(35498 + 487) == 0.0135 roughtly ~1.35% This argument does not stand anymore. We leave 'holes' in classes in ~98% of the cases. code that I used to gather those stats: --- diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c index 55cfda8..894773a 100644 --- a/mm/zsmalloc.c +++ b/mm/zsmalloc.c @@ -253,6 +253,9 @@ struct zs_pool { #ifdef CONFIG_ZSMALLOC_STAT struct dentry *stat_dentry; #endif + int compaction_nr; + long full_compact; + long part_compact; }; /* @@ -1717,6 +1720,7 @@ static void __zs_compact(struct zs_pool *pool, struct size_class *class) struct zs_compact_control cc; struct page *src_page; struct page *dst_page = NULL; + bool compacted = false; spin_lock(&class->lock); while ((src_page = isolate_source_page(class))) { @@ -1726,6 +1730,8 @@ static void __zs_compact(struct zs_pool *pool, struct size_class *class) if (!zs_can_compact(class)) break; + compacted = true; + cc.index = 0; cc.s_page = src_page; @@ -1751,6 +1757,13 @@ out: if (src_page) putback_zspage(pool, class, src_page); + if (compacted) { + if (zs_stat_get(class, OBJ_ALLOCATED) == zs_stat_get(class, OBJ_USED)) + pool->full_compact++; + else + pool->part_compact++; + } + spin_unlock(&class->lock); } @@ -1767,6 +1780,11 @@ unsigned long zs_compact(struct zs_pool *pool) continue; __zs_compact(pool, class); } + + pool->compaction_nr++; + pr_err("pool compaction nr:%d (full:%ld part:%ld)\n", pool->compaction_nr, + pool->full_compact, pool->part_compact); + return pool->num_migrated; } EXPORT_SYMBOL_GPL(zs_compact); -- 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: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2015-06-17 7:10 UTC|newest] Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top 2015-06-05 12:03 [RFC][PATCHv2 0/8] introduce automatic pool compaction Sergey Senozhatsky 2015-06-05 12:03 ` Sergey Senozhatsky 2015-06-05 12:03 ` [RFC][PATCHv2 1/8] zsmalloc: drop unused variable `nr_to_migrate' Sergey Senozhatsky 2015-06-05 12:03 ` Sergey Senozhatsky 2015-06-05 12:03 ` [RFC][PATCHv2 2/8] zsmalloc: partial page ordering within a fullness_list Sergey Senozhatsky 2015-06-05 12:03 ` Sergey Senozhatsky 2015-06-16 13:19 ` Minchan Kim 2015-06-16 13:19 ` Minchan Kim 2015-06-16 14:30 ` Sergey Senozhatsky 2015-06-16 14:30 ` Sergey Senozhatsky 2015-06-05 12:03 ` [RFC][PATCHv2 3/8] zsmalloc: lower ZS_ALMOST_FULL waterline Sergey Senozhatsky 2015-06-05 12:03 ` Sergey Senozhatsky 2015-06-16 13:37 ` Minchan Kim 2015-06-16 13:37 ` Minchan Kim 2015-06-16 14:35 ` Sergey Senozhatsky 2015-06-16 14:35 ` Sergey Senozhatsky 2015-06-05 12:03 ` [RFC][PATCHv2 4/8] zsmalloc: always keep per-class stats Sergey Senozhatsky 2015-06-05 12:03 ` Sergey Senozhatsky 2015-06-05 12:03 ` [RFC][PATCHv2 5/8] zsmalloc: introduce zs_can_compact() function Sergey Senozhatsky 2015-06-05 12:03 ` Sergey Senozhatsky 2015-06-16 14:19 ` Minchan Kim 2015-06-16 14:19 ` Minchan Kim 2015-06-16 14:41 ` Sergey Senozhatsky 2015-06-16 14:41 ` Sergey Senozhatsky 2015-06-05 12:03 ` [RFC][PATCHv2 6/8] zsmalloc: cosmetic compaction code adjustments Sergey Senozhatsky 2015-06-05 12:03 ` Sergey Senozhatsky 2015-06-05 12:03 ` [RFC][PATCHv2 7/8] zsmalloc/zram: move `num_migrated' to zs_pool Sergey Senozhatsky 2015-06-05 12:03 ` Sergey Senozhatsky 2015-06-05 12:03 ` [RFC][PATCHv2 8/8] zsmalloc: register a shrinker to trigger auto-compaction Sergey Senozhatsky 2015-06-05 12:03 ` Sergey Senozhatsky 2015-06-16 14:47 ` Minchan Kim 2015-06-16 14:47 ` Minchan Kim 2015-06-16 15:45 ` Sergey Senozhatsky 2015-06-16 15:45 ` Sergey Senozhatsky 2015-06-18 1:50 ` Minchan Kim 2015-06-18 1:50 ` Minchan Kim 2015-06-18 2:41 ` Sergey Senozhatsky 2015-06-18 2:41 ` Sergey Senozhatsky 2015-06-18 3:01 ` Sergey Senozhatsky 2015-06-18 3:01 ` Sergey Senozhatsky 2015-06-18 3:46 ` Minchan Kim 2015-06-18 3:46 ` Minchan Kim 2015-06-18 3:39 ` Minchan Kim 2015-06-18 3:39 ` Minchan Kim 2015-06-18 3:58 ` Sergey Senozhatsky 2015-06-18 3:58 ` Sergey Senozhatsky 2015-06-17 7:11 ` Sergey Senozhatsky [this message] 2015-06-17 7:11 ` Sergey Senozhatsky 2015-06-10 0:04 ` [RFC][PATCHv2 0/8] introduce automatic pool compaction Minchan Kim 2015-06-10 0:04 ` Minchan Kim 2015-06-10 0:07 ` Sergey Senozhatsky 2015-06-10 0:07 ` Sergey Senozhatsky
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