From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752794AbbFPOl5 (ORCPT ); Tue, 16 Jun 2015 10:41:57 -0400 Received: from mail-pd0-f177.google.com ([209.85.192.177]:35693 "EHLO mail-pd0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753890AbbFPOlt (ORCPT ); Tue, 16 Jun 2015 10:41:49 -0400 Date: Tue, 16 Jun 2015 23:41:06 +0900 From: Sergey Senozhatsky To: Minchan Kim Cc: Sergey Senozhatsky , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Sergey Senozhatsky Subject: Re: [RFC][PATCHv2 5/8] zsmalloc: introduce zs_can_compact() function Message-ID: <20150616144106.GD20596@swordfish> References: <1433505838-23058-1-git-send-email-sergey.senozhatsky@gmail.com> <1433505838-23058-6-git-send-email-sergey.senozhatsky@gmail.com> <20150616141914.GC31387@blaptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150616141914.GC31387@blaptop> User-Agent: Mutt/1.5.23+89 (0255b37be491) (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (06/16/15 23:19), Minchan Kim wrote: > On Fri, Jun 05, 2015 at 09:03:55PM +0900, Sergey Senozhatsky wrote: > > 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 > > Please use clear term. We have been used zspage as cluster of pages. > > maxobjs-per-zspage:4 > OK, will correct. class size sats[OBJ_ALLOCATED] stats[OBJ_USED] get_maxobj_per_zspage() +pages-per-zspage zspages-to-free > And say what is pages-per-zspage for each class. > then, write how you calculate it for easy reviewing. > > * class-3072 > * pages-per-zspage: 3 > * maxobjs-per-zspage = 4 > > In your example, allocated obj = 24652 and inuse obj = 24628 > so 24652 - 24628 = 24 = 4(ie, maxobjs-per-zspage) * 6 > so we can save 6 zspage. A zspage includes 3 pages so we can > save 3 * 6 = 18 pages via compaction. > > [..] > > + * Make sure that we actually can compact this class, > > + * IOW if migration will empty at least one page. > > free at least one zspage OK. > > + * > > + * 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); > > I don't think we need division and make it simple. > > return obj_wasted >= get_maxobj_per_zspage I use this number later for the shrinker, as a shrinker.count_objects() return value (total number of zsages that can be freed). -ss From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f43.google.com (mail-pa0-f43.google.com [209.85.220.43]) by kanga.kvack.org (Postfix) with ESMTP id 042EA6B0038 for ; Tue, 16 Jun 2015 10:41:50 -0400 (EDT) Received: by pacyx8 with SMTP id yx8so14134160pac.2 for ; Tue, 16 Jun 2015 07:41:49 -0700 (PDT) Received: from mail-pd0-x22a.google.com (mail-pd0-x22a.google.com. [2607:f8b0:400e:c02::22a]) by mx.google.com with ESMTPS id yf2si1641109pbb.223.2015.06.16.07.41.49 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 16 Jun 2015 07:41:49 -0700 (PDT) Received: by pdjn11 with SMTP id n11so15932656pdj.0 for ; Tue, 16 Jun 2015 07:41:49 -0700 (PDT) Date: Tue, 16 Jun 2015 23:41:06 +0900 From: Sergey Senozhatsky Subject: Re: [RFC][PATCHv2 5/8] zsmalloc: introduce zs_can_compact() function Message-ID: <20150616144106.GD20596@swordfish> References: <1433505838-23058-1-git-send-email-sergey.senozhatsky@gmail.com> <1433505838-23058-6-git-send-email-sergey.senozhatsky@gmail.com> <20150616141914.GC31387@blaptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150616141914.GC31387@blaptop> Sender: owner-linux-mm@kvack.org List-ID: To: Minchan Kim Cc: Sergey Senozhatsky , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Sergey Senozhatsky On (06/16/15 23:19), Minchan Kim wrote: > On Fri, Jun 05, 2015 at 09:03:55PM +0900, Sergey Senozhatsky wrote: > > 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 > > Please use clear term. We have been used zspage as cluster of pages. > > maxobjs-per-zspage:4 > OK, will correct. class size sats[OBJ_ALLOCATED] stats[OBJ_USED] get_maxobj_per_zspage() +pages-per-zspage zspages-to-free > And say what is pages-per-zspage for each class. > then, write how you calculate it for easy reviewing. > > * class-3072 > * pages-per-zspage: 3 > * maxobjs-per-zspage = 4 > > In your example, allocated obj = 24652 and inuse obj = 24628 > so 24652 - 24628 = 24 = 4(ie, maxobjs-per-zspage) * 6 > so we can save 6 zspage. A zspage includes 3 pages so we can > save 3 * 6 = 18 pages via compaction. > > [..] > > + * Make sure that we actually can compact this class, > > + * IOW if migration will empty at least one page. > > free at least one zspage OK. > > + * > > + * 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); > > I don't think we need division and make it simple. > > return obj_wasted >= get_maxobj_per_zspage I use this number later for the shrinker, as a shrinker.count_objects() return value (total number of zsages that can be freed). -ss -- 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