From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f182.google.com (mail-pd0-f182.google.com [209.85.192.182]) by kanga.kvack.org (Postfix) with ESMTP id 160096B0032 for ; Mon, 29 Jun 2015 19:36:03 -0400 (EDT) Received: by pdjn11 with SMTP id n11so125154168pdj.0 for ; Mon, 29 Jun 2015 16:36:02 -0700 (PDT) Received: from mail-pa0-x22d.google.com (mail-pa0-x22d.google.com. [2607:f8b0:400e:c03::22d]) by mx.google.com with ESMTPS id o8si66850089pdp.62.2015.06.29.16.36.02 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 29 Jun 2015 16:36:02 -0700 (PDT) Received: by pactm7 with SMTP id tm7so111826972pac.2 for ; Mon, 29 Jun 2015 16:36:01 -0700 (PDT) Date: Tue, 30 Jun 2015 08:36:30 +0900 From: Sergey Senozhatsky Subject: Re: [RFC][PATCHv3 7/7] zsmalloc: register a shrinker to trigger auto-compaction Message-ID: <20150629233630.GA7301@swordfish> References: <1434628004-11144-1-git-send-email-sergey.senozhatsky@gmail.com> <1434628004-11144-8-git-send-email-sergey.senozhatsky@gmail.com> <20150629070711.GD13179@bbox> <20150629085744.GA549@swordfish> <20150629133956.GA15331@blaptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150629133956.GA15331@blaptop> Sender: owner-linux-mm@kvack.org List-ID: To: Minchan Kim Cc: Sergey Senozhatsky , Sergey Senozhatsky , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org On (06/29/15 22:39), Minchan Kim wrote: > Hi Sergey, > > Sorry for too late reply. > Hello Minchan, Sure, no problem. Will send out a new patchset later today. Thanks. -ss > On Mon, Jun 29, 2015 at 05:57:44PM +0900, Sergey Senozhatsky wrote: > > Hello, > > > > thanks for review. > > > > On (06/29/15 16:07), Minchan Kim wrote: > > [..] > > > > if (!migrate_zspage(pool, class, &cc)) > > > > - break; > > > > + goto out; > > > > > > It should retry with another target_page instead of going out. > > > > yep. > > > > [..] > > > > +static unsigned long zs_shrinker_scan(struct shrinker *shrinker, > > > > + struct shrink_control *sc) > > > > +{ > > [..] > > > > > > Returns migrated object count. > > > > > [..] > > > > +static unsigned long zs_shrinker_count(struct shrinker *shrinker, > > > > + struct shrink_control *sc) > > > > +{ > > [..] > > > > > > But it returns wasted_obj / max_obj_per_zspage? > > > > > > > Good catch. > > So, __zs_compact() and zs_shrinker_count() are ok. Returning > > "wasted_obj / max_obj_per_zspage" from zs_can_compact() makes > > sense there. The only place is zs_shrinker_scan()->zs_compact(). > > I want to make zs_can_compact return freeable page unit. > > ie, > > return obj_wasted * class->pages_per_zspage; > > and let's make __zs_compact returns the number of freed pages. > > IOW, I like your (c). > > > > > Hm, I can think of: > > > > (a) We can change zs_compact() to return the total number of > > freed zspages. That will not really change a user visible > > interface. We export (fwiw) the number of compacted objects > > in mm_stat. Basically, this is internal zsmalloc() counter and > > no user space program can ever do anything with that data. From > > that prospective we will just replace one senseless number with > > another (equally meaningless) one. > > > > > > (b) replace zs_compact() call in zs_shrinker_scan() with a class loop > > > > 1764 int i; > > 1765 unsigned long nr_migrated = 0; > > 1766 struct size_class *class; > > 1767 > > 1768 for (i = zs_size_classes - 1; i >= 0; i--) { > > 1769 class = pool->size_class[i]; > > 1770 if (!class) > > 1771 continue; > > 1772 if (class->index != i) > > 1773 continue; > > 1774 nr_migrated += __zs_compact(pool, class); > > 1775 } > > 1776 > > 1777 return nr_migrated; > > > > But on every iteration increment nr_migrated with > > "nr_migrated += just_migrated / max_obj_per_zspage" > > > > (which will be unnecessary if zs_compact() will return the number of freed > > zspages). > > > > So, (b) is mostly fine, except that we already have several pool->size_class > > loops, with same `if (!class)' and `if (class->index...)' checks; and it > > asks for some sort of refactoring or... a tricky for_each_class() define. > > > > > > In both cases, however, we don't tell anything valuable to user space. > > Thus, > > > > (c) Return from zs_compact() the number of pages (PAGE_SIZE) freed. > > And change compaction to operate in terms of pages (PAGE_SIZE). At > > least mm_stat::compacted will turn into something useful for user > > space. > > Yes. > > Thanks. > > > > > -ss > > -- > Kind regards, > Minchan Kim > -- 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