From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jaegeuk Kim Subject: Re: [PATCH 2/3] f2fs: schedule in between two continous batch discards Date: Thu, 25 Aug 2016 09:57:16 -0700 Message-ID: <20160825165716.GA84318@jaegeuk> References: <1471792891-2388-1-git-send-email-chao@kernel.org> <1471792891-2388-2-git-send-email-chao@kernel.org> <20160823165353.GA73835@jaegeuk> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from sog-mx-3.v43.ch3.sourceforge.com ([172.29.43.193] helo=mx.sourceforge.net) by sfs-ml-3.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1bcxy2-00052O-SN for linux-f2fs-devel@lists.sourceforge.net; Thu, 25 Aug 2016 16:57:26 +0000 Received: from mail.kernel.org ([198.145.29.136]) by sog-mx-3.v43.ch3.sourceforge.com with esmtps (TLSv1:AES256-SHA:256) (Exim 4.76) id 1bcxy0-00017u-Rn for linux-f2fs-devel@lists.sourceforge.net; Thu, 25 Aug 2016 16:57:26 +0000 Content-Disposition: inline In-Reply-To: List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net To: Chao Yu Cc: Chao Yu , linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net Hi Chao, On Thu, Aug 25, 2016 at 05:22:29PM +0800, Chao Yu wrote: > Hi Jaegeuk, > > On 2016/8/24 0:53, Jaegeuk Kim wrote: > > Hi Chao, > > > > On Sun, Aug 21, 2016 at 11:21:30PM +0800, Chao Yu wrote: > >> From: Chao Yu > >> > >> In batch discard approach of fstrim will grab/release gc_mutex lock > >> repeatly, it makes contention of the lock becoming more intensive. > >> > >> So after one batch discards were issued in checkpoint and the lock > >> was released, it's better to do schedule() to increase opportunity > >> of grabbing gc_mutex lock for other competitors. > >> > >> Signed-off-by: Chao Yu > >> --- > >> fs/f2fs/segment.c | 2 ++ > >> 1 file changed, 2 insertions(+) > >> > >> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c > >> index 020767c..d0f74eb 100644 > >> --- a/fs/f2fs/segment.c > >> +++ b/fs/f2fs/segment.c > >> @@ -1305,6 +1305,8 @@ int f2fs_trim_fs(struct f2fs_sb_info *sbi, struct fstrim_range *range) > >> mutex_unlock(&sbi->gc_mutex); > >> if (err) > >> break; > >> + > >> + schedule(); > > > > Hmm, if other thread is already waiting for gc_mutex, we don't need this here. > > In order to avoid long latency, wouldn't it be enough to reduce the batch size? > > Hmm, when fstrim call mutex_unlock we will pop one blocked locker from FIFO list > of mutex lock, and wake it up, then fstrimer will try to lock gc_mutex for next > batch trim, so the popped locker and fstrimer will make a new competition in > gc_mutex. Before trying to grab gc_mutex by fstrim again, there are already blocked tasks waiting for gc_mutex. Hence the next one should be selectec by FIFO, no? Thanks, > If fstrimer is running in a big core, and popped locker is running in > a small core, we can't guarantee popped locker can win the race, and for the > most of time, fstrimer will win. So in order to reduce starvation of other > gc_mutext locker, it's better to do schedule() here. > > Thanks, > > > > > Thanks, > > > >> } > >> out: > >> range->len = F2FS_BLK_TO_BYTES(cpc.trimmed); > >> -- > >> 2.7.2 > > > > . > > ------------------------------------------------------------------------------ From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756867AbcHYRWx (ORCPT ); Thu, 25 Aug 2016 13:22:53 -0400 Received: from mail.kernel.org ([198.145.29.136]:40934 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751350AbcHYRWu (ORCPT ); Thu, 25 Aug 2016 13:22:50 -0400 Date: Thu, 25 Aug 2016 09:57:16 -0700 From: Jaegeuk Kim To: Chao Yu Cc: Chao Yu , linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/3] f2fs: schedule in between two continous batch discards Message-ID: <20160825165716.GA84318@jaegeuk> References: <1471792891-2388-1-git-send-email-chao@kernel.org> <1471792891-2388-2-git-send-email-chao@kernel.org> <20160823165353.GA73835@jaegeuk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.6.0 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Chao, On Thu, Aug 25, 2016 at 05:22:29PM +0800, Chao Yu wrote: > Hi Jaegeuk, > > On 2016/8/24 0:53, Jaegeuk Kim wrote: > > Hi Chao, > > > > On Sun, Aug 21, 2016 at 11:21:30PM +0800, Chao Yu wrote: > >> From: Chao Yu > >> > >> In batch discard approach of fstrim will grab/release gc_mutex lock > >> repeatly, it makes contention of the lock becoming more intensive. > >> > >> So after one batch discards were issued in checkpoint and the lock > >> was released, it's better to do schedule() to increase opportunity > >> of grabbing gc_mutex lock for other competitors. > >> > >> Signed-off-by: Chao Yu > >> --- > >> fs/f2fs/segment.c | 2 ++ > >> 1 file changed, 2 insertions(+) > >> > >> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c > >> index 020767c..d0f74eb 100644 > >> --- a/fs/f2fs/segment.c > >> +++ b/fs/f2fs/segment.c > >> @@ -1305,6 +1305,8 @@ int f2fs_trim_fs(struct f2fs_sb_info *sbi, struct fstrim_range *range) > >> mutex_unlock(&sbi->gc_mutex); > >> if (err) > >> break; > >> + > >> + schedule(); > > > > Hmm, if other thread is already waiting for gc_mutex, we don't need this here. > > In order to avoid long latency, wouldn't it be enough to reduce the batch size? > > Hmm, when fstrim call mutex_unlock we will pop one blocked locker from FIFO list > of mutex lock, and wake it up, then fstrimer will try to lock gc_mutex for next > batch trim, so the popped locker and fstrimer will make a new competition in > gc_mutex. Before trying to grab gc_mutex by fstrim again, there are already blocked tasks waiting for gc_mutex. Hence the next one should be selectec by FIFO, no? Thanks, > If fstrimer is running in a big core, and popped locker is running in > a small core, we can't guarantee popped locker can win the race, and for the > most of time, fstrimer will win. So in order to reduce starvation of other > gc_mutext locker, it's better to do schedule() here. > > Thanks, > > > > > Thanks, > > > >> } > >> out: > >> range->len = F2FS_BLK_TO_BYTES(cpc.trimmed); > >> -- > >> 2.7.2 > > > > . > >