From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751652AbZHQFIr (ORCPT ); Mon, 17 Aug 2009 01:08:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751297AbZHQFIq (ORCPT ); Mon, 17 Aug 2009 01:08:46 -0400 Received: from rv-out-0506.google.com ([209.85.198.230]:65064 "EHLO rv-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751274AbZHQFIp (ORCPT ); Mon, 17 Aug 2009 01:08:45 -0400 Message-ID: <4A88E5CC.6050706@vflare.org> Date: Mon, 17 Aug 2009 10:38:28 +0530 From: Nitin Gupta Reply-To: ngupta@vflare.org User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.1) Gecko/20090814 Fedora/3.0-2.6.b3.fc11 Thunderbird/3.0b3 MIME-Version: 1.0 To: KAMEZAWA Hiroyuki CC: mingo@elte.hu, linux-kernel@vger.kernel.org Subject: Re: [PATCH] swap: send callback when swap slot is freed References: <200908122007.43522.ngupta@vflare.org> <20090817115529.59395cea.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20090817115529.59395cea.kamezawa.hiroyu@jp.fujitsu.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/17/2009 08:25 AM, KAMEZAWA Hiroyuki wrote: > On Wed, 12 Aug 2009 20:07:43 +0530 > Nitin Gupta wrote: > >> Currently, we have "swap discard" mechanism which sends a discard bio request >> when we find a free cluster during scan_swap_map(). This callback can come a >> long time after swap slots are actually freed. >> >> This delay in callback is a great problem when (compressed) RAM [1] is used >> as a swap device. So, this change adds a callback which is called as >> soon as a swap slot becomes free. For above mentioned case of swapping >> over compressed RAM device, this is very useful since we can immediately >> free memory allocated for this swap page. >> >> This callback does not replace swap discard support. It is called with >> swap_lock held, so it is meant to trigger action that finishes quickly. >> However, swap discard is an I/O request and can be used for taking longer >> actions. >> >> Links: >> [1] http://code.google.com/p/compcache/ >> > > Hmm, do you really need notify at *every* swap free ? > No batching is necessary ? > We need notify for every swap free and no batching is desired, at least for compcache case. Thanks, Nitin