From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with ESMTP id DEEF46B006A for ; Thu, 7 Oct 2010 21:24:23 -0400 (EDT) Date: Fri, 8 Oct 2010 10:12:22 +0900 From: Daisuke Nishimura Subject: Re: [PATCH v2] memcg: reduce lock time at move charge (Was Re: [PATCH 04/10] memcg: disable local interrupts in lock_page_cgroup() Message-Id: <20101008101222.1aab03ae.nishimura@mxp.nes.nec.co.jp> In-Reply-To: <20101007161454.84570cf9.akpm@linux-foundation.org> References: <1286175485-30643-1-git-send-email-gthelen@google.com> <1286175485-30643-5-git-send-email-gthelen@google.com> <20101005160332.GB9515@barrios-desktop> <20101007093545.429fe04a.kamezawa.hiroyu@jp.fujitsu.com> <20101007105456.d86d8092.nishimura@mxp.nes.nec.co.jp> <20101007111743.322c3993.kamezawa.hiroyu@jp.fujitsu.com> <20101007152111.df687a62.kamezawa.hiroyu@jp.fujitsu.com> <20101007162811.c3a35be9.nishimura@mxp.nes.nec.co.jp> <20101007164204.83b207c6.kamezawa.hiroyu@jp.fujitsu.com> <20101007170405.27ed964c.kamezawa.hiroyu@jp.fujitsu.com> <20101007161454.84570cf9.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Andrew Morton Cc: KAMEZAWA Hiroyuki , Minchan Kim , Greg Thelen , linux-kernel@vger.kernel.org, linux-mm@kvack.org, containers@lists.osdl.org, Andrea Righi , Balbir Singh , Daisuke Nishimura List-ID: On Thu, 7 Oct 2010 16:14:54 -0700 Andrew Morton wrote: > On Thu, 7 Oct 2010 17:04:05 +0900 > KAMEZAWA Hiroyuki wrote: > > > Now, at task migration among cgroup, memory cgroup scans page table and moving > > account if flags are properly set. > > > > The core code, mem_cgroup_move_charge_pte_range() does > > > > pte_offset_map_lock(); > > for all ptes in a page table: > > 1. look into page table, find_and_get a page > > 2. remove it from LRU. > > 3. move charge. > > 4. putback to LRU. put_page() > > pte_offset_map_unlock(); > > > > for pte entries on a 3rd level? page table. > > > > This pte_offset_map_lock seems a bit long. This patch modifies a rountine as > > > > for 32 pages: pte_offset_map_lock() > > find_and_get a page > > record it > > pte_offset_map_unlock() > > for all recorded pages > > isolate it from LRU. > > move charge > > putback to LRU > > for all recorded pages > > put_page() > > The patch makes the code larger, more complex and slower! > Before this patch: text data bss dec hex filename 27163 11782 4100 43045 a825 mm/memcontrol.o After this patch: text data bss dec hex filename 27307 12294 4100 43701 aab5 mm/memcontrol.o hmm, allocating mc.target[] statically might be bad, but I'm now wondering whether I could allocate mc itself dynamically(I'll try). > I do think we're owed a more complete description of its benefits than > "seems a bit long". Have problems been observed? Any measurements > taken? > IIUC, this patch is necessary for "[PATCH] memcg: lock-free clear page writeback" later, but I agree we should describe it. Thanks, Daisuke Nishimura. -- 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