From mboxrd@z Thu Jan 1 00:00:00 1970 From: Johannes Weiner Subject: Re: [PATCH 3/3] fs, mm: account buffer_head to kmemcg Date: Tue, 19 Jun 2018 12:27:41 -0400 Message-ID: <20180619162741.GC27423@cmpxchg.org> References: <20180619051327.149716-1-shakeelb@google.com> <20180619051327.149716-4-shakeelb@google.com> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=cmpxchg.org ; s=x; h=In-Reply-To:Content-Type:MIME-Version:References:Message-ID:Subject: Cc:To:From:Date:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=IjzRyh3dGjs3iY1KTmpl8JPs/rIgpmEkG8uepgThUhg=; b=nd7imqtf/Bt7PIXzfoMP72TpvJ fcVl5OhKp5LuMWMtBUzrPXPexpbfBrKHpgX7cPhiUwFi700FVyXbJ15hbfZ8W/XH5wMX62k9qiK9M 1yqEscaFfNPDQwB1xjupB5TmDP0srDPuWD8XtBQfssqtlhrioexcIeIw2/B1SwcVsumM=; Content-Disposition: inline In-Reply-To: <20180619051327.149716-4-shakeelb@google.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Shakeel Butt Cc: Andrew Morton , Michal Hocko , Vladimir Davydov , Jan Kara , Greg Thelen , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Jan Kara , Alexander Viro On Mon, Jun 18, 2018 at 10:13:27PM -0700, Shakeel Butt wrote: > The buffer_head can consume a significant amount of system memory and > is directly related to the amount of page cache. In our production > environment we have observed that a lot of machines are spending a > significant amount of memory as buffer_head and can not be left as > system memory overhead. > > Charging buffer_head is not as simple as adding __GFP_ACCOUNT to the > allocation. The buffer_heads can be allocated in a memcg different from > the memcg of the page for which buffer_heads are being allocated. One > concrete example is memory reclaim. The reclaim can trigger I/O of pages > of any memcg on the system. So, the right way to charge buffer_head is > to extract the memcg from the page for which buffer_heads are being > allocated and then use targeted memcg charging API. > > Signed-off-by: Shakeel Butt > Cc: Jan Kara > Cc: Greg Thelen > Cc: Michal Hocko > Cc: Johannes Weiner > Cc: Vladimir Davydov > Cc: Alexander Viro > Cc: Andrew Morton > --- > fs/buffer.c | 14 +++++++++++++- > include/linux/memcontrol.h | 7 +++++++ > mm/memcontrol.c | 21 +++++++++++++++++++++ > 3 files changed, 41 insertions(+), 1 deletion(-) > > diff --git a/fs/buffer.c b/fs/buffer.c > index 8194e3049fc5..26389b7a3cab 100644 > --- a/fs/buffer.c > +++ b/fs/buffer.c > @@ -815,10 +815,17 @@ struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size, > struct buffer_head *bh, *head; > gfp_t gfp = GFP_NOFS; > long offset; > + struct mem_cgroup *old_memcg; > + struct mem_cgroup *memcg = get_mem_cgroup_from_page(page); > > if (retry) > gfp |= __GFP_NOFAIL; > > + if (memcg) { > + gfp |= __GFP_ACCOUNT; > + old_memcg = memalloc_memcg_save(memcg); > + } Please move the get_mem_cgroup_from_page() call out of the declarations and down to right before the if (memcg) branch. > head = NULL; > offset = PAGE_SIZE; > while ((offset -= size) >= 0) { > @@ -835,6 +842,11 @@ struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size, > /* Link the buffer to its page */ > set_bh_page(bh, page, offset); > } > +out: > + if (memcg) { > + memalloc_memcg_restore(old_memcg); > +#ifdef CONFIG_MEMCG > + css_put(&memcg->css); > +#endif Please add a put_mem_cgroup() ;) Otherwise this looks fine to me.