From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f49.google.com (mail-pa0-f49.google.com [209.85.220.49]) by kanga.kvack.org (Postfix) with ESMTP id B0B9C6B003A for ; Wed, 13 Aug 2014 11:15:06 -0400 (EDT) Received: by mail-pa0-f49.google.com with SMTP id hz1so14840437pad.8 for ; Wed, 13 Aug 2014 08:15:06 -0700 (PDT) Received: from mail-pd0-x22b.google.com (mail-pd0-x22b.google.com [2607:f8b0:400e:c02::22b]) by mx.google.com with ESMTPS id hr10si1746499pac.24.2014.08.13.08.15.05 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 13 Aug 2014 08:15:05 -0700 (PDT) Received: by mail-pd0-f171.google.com with SMTP id z10so14655932pdj.30 for ; Wed, 13 Aug 2014 08:15:05 -0700 (PDT) Date: Thu, 14 Aug 2014 00:13:54 +0900 From: Sergey Senozhatsky Subject: Re: [RFC 1/3] zsmalloc: move pages_allocated to zs_pool Message-ID: <20140813151354.GD1091@swordfish> References: <1407225723-23754-1-git-send-email-minchan@kernel.org> <1407225723-23754-2-git-send-email-minchan@kernel.org> <20140813141413.GA1091@swordfish> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Dan Streetman Cc: Sergey Senozhatsky , Minchan Kim , Linux-MM , linux-kernel , Jerome Marchand , juno.choi@lge.com, seungho1.park@lge.com, Luigi Semenzato , Nitin Gupta On (08/13/14 10:51), Dan Streetman wrote: > Date: Wed, 13 Aug 2014 10:51:40 -0400 > From: Dan Streetman > To: Sergey Senozhatsky > Cc: Minchan Kim , Linux-MM , > linux-kernel , Jerome Marchand > , juno.choi@lge.com, seungho1.park@lge.com, Luigi > Semenzato , Nitin Gupta > Subject: Re: [RFC 1/3] zsmalloc: move pages_allocated to zs_pool > > On Wed, Aug 13, 2014 at 10:14 AM, Sergey Senozhatsky > wrote: > > On (08/13/14 09:59), Dan Streetman wrote: > >> On Tue, Aug 5, 2014 at 4:02 AM, Minchan Kim wrote: > >> > Pages_allocated has counted in size_class structure and when user > >> > want to see total_size_bytes, it gathers all of value from each > >> > size_class to report the sum. > >> > > >> > It's not bad if user don't see the value often but if user start > >> > to see the value frequently, it would be not a good deal for > >> > performance POV. > >> > > >> > This patch moves the variable from size_class to zs_pool so it would > >> > reduce memory footprint (from [255 * 8byte] to [sizeof(atomic_t)]) > >> > but it adds new locking overhead but it wouldn't be severe because > >> > it's not a hot path in zs_malloc(ie, it is called only when new > >> > zspage is created, not a object). > >> > >> Would using an atomic64_t without locking be simpler? > > > > it would be racy. > > oh. atomic operations aren't smp safe? is that because other > processors might use a stale value, and barriers must be added? I > guess I don't quite understand the value of atomic then. :-/ pool not only set the value, it also read it and make some decisions based on that value: pages_allocated += X if (pages_allocated >= max_pages_allocated) return 0; -ss > >> > >> > > >> > Signed-off-by: Minchan Kim > >> > --- > >> > mm/zsmalloc.c | 30 ++++++++++++++++-------------- > >> > 1 file changed, 16 insertions(+), 14 deletions(-) > >> > > >> > diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c > >> > index fe78189624cf..a6089bd26621 100644 > >> > --- a/mm/zsmalloc.c > >> > +++ b/mm/zsmalloc.c > >> > @@ -198,9 +198,6 @@ struct size_class { > >> > > >> > spinlock_t lock; > >> > > >> > - /* stats */ > >> > - u64 pages_allocated; > >> > - > >> > struct page *fullness_list[_ZS_NR_FULLNESS_GROUPS]; > >> > }; > >> > > >> > @@ -216,9 +213,12 @@ struct link_free { > >> > }; > >> > > >> > struct zs_pool { > >> > + spinlock_t stat_lock; > >> > + > >> > struct size_class size_class[ZS_SIZE_CLASSES]; > >> > > >> > gfp_t flags; /* allocation flags used when growing pool */ > >> > + unsigned long pages_allocated; > >> > }; > >> > > >> > /* > >> > @@ -882,6 +882,7 @@ struct zs_pool *zs_create_pool(gfp_t flags) > >> > > >> > } > >> > > >> > + spin_lock_init(&pool->stat_lock); > >> > pool->flags = flags; > >> > > >> > return pool; > >> > @@ -943,8 +944,10 @@ unsigned long zs_malloc(struct zs_pool *pool, size_t size) > >> > return 0; > >> > > >> > set_zspage_mapping(first_page, class->index, ZS_EMPTY); > >> > + spin_lock(&pool->stat_lock); > >> > + pool->pages_allocated += class->pages_per_zspage; > >> > + spin_unlock(&pool->stat_lock); > >> > spin_lock(&class->lock); > >> > - class->pages_allocated += class->pages_per_zspage; > >> > } > >> > > >> > obj = (unsigned long)first_page->freelist; > >> > @@ -997,14 +1000,14 @@ void zs_free(struct zs_pool *pool, unsigned long obj) > >> > > >> > first_page->inuse--; > >> > fullness = fix_fullness_group(pool, first_page); > >> > - > >> > - if (fullness == ZS_EMPTY) > >> > - class->pages_allocated -= class->pages_per_zspage; > >> > - > >> > spin_unlock(&class->lock); > >> > > >> > - if (fullness == ZS_EMPTY) > >> > + if (fullness == ZS_EMPTY) { > >> > + spin_lock(&pool->stat_lock); > >> > + pool->pages_allocated -= class->pages_per_zspage; > >> > + spin_unlock(&pool->stat_lock); > >> > free_zspage(first_page); > >> > + } > >> > } > >> > EXPORT_SYMBOL_GPL(zs_free); > >> > > >> > @@ -1100,12 +1103,11 @@ EXPORT_SYMBOL_GPL(zs_unmap_object); > >> > > >> > u64 zs_get_total_size_bytes(struct zs_pool *pool) > >> > { > >> > - int i; > >> > - u64 npages = 0; > >> > - > >> > - for (i = 0; i < ZS_SIZE_CLASSES; i++) > >> > - npages += pool->size_class[i].pages_allocated; > >> > + u64 npages; > >> > > >> > + spin_lock(&pool->stat_lock); > >> > + npages = pool->pages_allocated; > >> > + spin_unlock(&pool->stat_lock); > >> > return npages << PAGE_SHIFT; > >> > } > >> > EXPORT_SYMBOL_GPL(zs_get_total_size_bytes); > >> > -- > >> > 2.0.0 > >> > > >> > -- > >> > 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 > >> > -- 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