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Violators will be prosecuted for from ; Thu, 8 Feb 2018 16:30:12 -0000 Date: Thu, 8 Feb 2018 18:30:07 +0200 From: Mike Rapoport Subject: Re: [PATCH 1/2] zsmalloc: introduce zs_huge_object() function References: <20180207092919.19696-1-sergey.senozhatsky@gmail.com> <20180207092919.19696-2-sergey.senozhatsky@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180207092919.19696-2-sergey.senozhatsky@gmail.com> Message-Id: <20180208163006.GB17354@rapoport-lnx> Sender: owner-linux-mm@kvack.org List-ID: To: Sergey Senozhatsky Cc: Minchan Kim , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Sergey Senozhatsky On Wed, Feb 07, 2018 at 06:29:18PM +0900, Sergey Senozhatsky wrote: > Not every object can be share its zspage with other objects, e.g. > when the object is as big as zspage or nearly as big a zspage. > For such objects zsmalloc has a so called huge class - every object > which belongs to huge class consumes the entire zspage (which > consists of a physical page). On x86_64, PAGE_SHIFT 12 box, the > first non-huge class size is 3264, so starting down from size 3264, > objects can share page(-s) and thus minimize memory wastage. > > ZRAM, however, has its own statically defined watermark for huge > objects - "3 * PAGE_SIZE / 4 = 3072", and forcibly stores every > object larger than this watermark (3072) as a PAGE_SIZE object, > in other words, to a huge class, while zsmalloc can keep some of > those objects in non-huge classes. This results in increased > memory consumption. > > zsmalloc knows better if the object is huge or not. Introduce > zs_huge_object() function which tells if the given object can be > stored in one of non-huge classes or not. This will let us to drop > ZRAM's huge object watermark and fully rely on zsmalloc when we > decide if the object is huge. > > Signed-off-by: Sergey Senozhatsky > --- > include/linux/zsmalloc.h | 2 ++ > mm/zsmalloc.c | 17 +++++++++++++++++ > 2 files changed, 19 insertions(+) > > diff --git a/include/linux/zsmalloc.h b/include/linux/zsmalloc.h > index 57a8e98f2708..9a1baf673cc1 100644 > --- a/include/linux/zsmalloc.h > +++ b/include/linux/zsmalloc.h > @@ -47,6 +47,8 @@ void zs_destroy_pool(struct zs_pool *pool); > unsigned long zs_malloc(struct zs_pool *pool, size_t size, gfp_t flags); > void zs_free(struct zs_pool *pool, unsigned long obj); > > +bool zs_huge_object(size_t sz); > + > void *zs_map_object(struct zs_pool *pool, unsigned long handle, > enum zs_mapmode mm); > void zs_unmap_object(struct zs_pool *pool, unsigned long handle); > diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c > index c3013505c305..b3e295a806be 100644 > --- a/mm/zsmalloc.c > +++ b/mm/zsmalloc.c > @@ -192,6 +192,7 @@ static struct vfsmount *zsmalloc_mnt; > * (see: fix_fullness_group()) > */ > static const int fullness_threshold_frac = 4; > +static size_t zs_huge_class_size; > > struct size_class { > spinlock_t lock; > @@ -1417,6 +1418,19 @@ void zs_unmap_object(struct zs_pool *pool, unsigned long handle) > } > EXPORT_SYMBOL_GPL(zs_unmap_object); > > +/* > + * Check if the object's size falls into huge_class area. We must take > + * ZS_HANDLE_SIZE into account and test the actual size we are going to > + * use up. zs_malloc() unconditionally adds handle size before it performs > + * size_class lookup, so we may endup in a huge class yet zs_huge_object() > + * returned 'false'. > + */ Can you please reformat this comment as kernel-doc? > +bool zs_huge_object(size_t sz) > +{ > + return sz + ZS_HANDLE_SIZE >= zs_huge_class_size; > +} > +EXPORT_SYMBOL_GPL(zs_huge_object); > + > static unsigned long obj_malloc(struct size_class *class, > struct zspage *zspage, unsigned long handle) > { > @@ -2404,6 +2418,9 @@ struct zs_pool *zs_create_pool(const char *name) > INIT_LIST_HEAD(&class->fullness_list[fullness]); > > prev_class = class; > + if (pages_per_zspage == 1 && objs_per_zspage == 1 > + && !zs_huge_class_size) > + zs_huge_class_size = size; > } > > /* debug only, don't abort if it fails */ > -- > 2.16.1 > > -- > 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 > -- Sincerely yours, Mike. -- 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