From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932780AbcISWMY (ORCPT ); Mon, 19 Sep 2016 18:12:24 -0400 Received: from mail.kernel.org ([198.145.29.136]:48410 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753020AbcISWMW (ORCPT ); Mon, 19 Sep 2016 18:12:22 -0400 Date: Mon, 19 Sep 2016 15:12:11 -0700 From: Jaegeuk Kim To: Chao Yu Cc: linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org Subject: Re: [PATCH] f2fs: fix to avoid slowing down background gc Message-ID: <20160919221211.GC68913@jaegeuk> References: <20160918115227.130658-1-yuchao0@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160918115227.130658-1-yuchao0@huawei.com> 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 Sun, Sep 18, 2016 at 07:52:27PM +0800, Chao Yu wrote: > Previously, we will choose to speed up background gc when the below > conditions are both satisfied: > a. There are a number of invalid blocks > b. There is not enough free space > > But, when space utilization is high (utilization > 60%), there will be > not enough invalid blocks, result in slowing down background gc, after > then there are more opportunities that triggering foreground gc due to > high fragmented free space in fs. > > Remove condition a) in order to avoid slow down background gc speed in > a high utilization fs. There exists a trade-off here: wear-out vs. eager gc for future speed-up. How about using a kind of f2fs's dirty level (e.g., BDF)? Thanks, > > Signed-off-by: Chao Yu > --- > fs/f2fs/gc.h | 18 +++--------------- > 1 file changed, 3 insertions(+), 15 deletions(-) > > diff --git a/fs/f2fs/gc.h b/fs/f2fs/gc.h > index a993967..5d0a19c 100644 > --- a/fs/f2fs/gc.h > +++ b/fs/f2fs/gc.h > @@ -16,7 +16,6 @@ > #define DEF_GC_THREAD_MIN_SLEEP_TIME 30000 /* milliseconds */ > #define DEF_GC_THREAD_MAX_SLEEP_TIME 60000 > #define DEF_GC_THREAD_NOGC_SLEEP_TIME 300000 /* wait 5 min */ > -#define LIMIT_INVALID_BLOCK 40 /* percentage over total user space */ > #define LIMIT_FREE_BLOCK 40 /* percentage over invalid + free space */ > > /* Search max. number of dirty segments to select a victim segment */ > @@ -52,11 +51,6 @@ static inline block_t free_user_blocks(struct f2fs_sb_info *sbi) > << sbi->log_blocks_per_seg; > } > > -static inline block_t limit_invalid_user_blocks(struct f2fs_sb_info *sbi) > -{ > - return (long)(sbi->user_block_count * LIMIT_INVALID_BLOCK) / 100; > -} > - > static inline block_t limit_free_user_blocks(struct f2fs_sb_info *sbi) > { > block_t reclaimable_user_blocks = sbi->user_block_count - > @@ -88,15 +82,9 @@ static inline void decrease_sleep_time(struct f2fs_gc_kthread *gc_th, > > static inline bool has_enough_invalid_blocks(struct f2fs_sb_info *sbi) > { > - block_t invalid_user_blocks = sbi->user_block_count - > - written_block_count(sbi); > /* > - * Background GC is triggered with the following conditions. > - * 1. There are a number of invalid blocks. > - * 2. There is not enough free space. > + * Background GC should speed up when there is not enough free blocks > + * in total unused (free + invalid) blocks. > */ > - if (invalid_user_blocks > limit_invalid_user_blocks(sbi) && > - free_user_blocks(sbi) < limit_free_user_blocks(sbi)) > - return true; > - return false; > + return free_user_blocks(sbi) < limit_free_user_blocks(sbi); > } > -- > 2.8.2.311.gee88674