From mboxrd@z Thu Jan 1 00:00:00 1970 From: Josef Bacik Subject: Re: [PATCH 1/6] btrfs: fix threshold calculation for block groups smaller than 1GB Date: Mon, 23 Aug 2010 09:02:25 -0400 Message-ID: <20100823130224.GA2404@localhost.localdomain> References: <4C71CD4B.10606@cn.fujitsu.com> <4C71CD60.5050507@cn.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Chris Mason , Josef Bacik , linux-btrfs@vger.kernel.org, LKML To: Li Zefan Return-path: In-Reply-To: <4C71CD60.5050507@cn.fujitsu.com> List-ID: On Mon, Aug 23, 2010 at 09:22:40AM +0800, Li Zefan wrote: > If a block group is smaller than 1GB, the extent entry threadhold > calculation will always set the threshold to 0. > > So as free space gets fragmented, btrfs will switch to use bitmap > to manage free space, but then will never switch back to extents > due to this bug. > > Signed-off-by: Li Zefan > --- > fs/btrfs/free-space-cache.c | 8 ++++++-- > 1 files changed, 6 insertions(+), 2 deletions(-) > > diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c > index f488fac..7edbef6 100644 > --- a/fs/btrfs/free-space-cache.c > +++ b/fs/btrfs/free-space-cache.c > @@ -263,14 +263,18 @@ static void recalculate_thresholds(struct btrfs_block_group_cache *block_group) > u64 max_bytes; > u64 bitmap_bytes; > u64 extent_bytes; > + u64 size = block_group->key.offset; > > /* > * The goal is to keep the total amount of memory used per 1gb of space > * at or below 32k, so we need to adjust how much memory we allow to be > * used by extent based free space tracking > */ > - max_bytes = MAX_CACHE_BYTES_PER_GIG * > - (div64_u64(block_group->key.offset, 1024 * 1024 * 1024)); > + if (size < 1024 * 1024 * 1024) > + max_bytes = MAX_CACHE_BYTES_PER_GIG; > + else > + max_bytes = MAX_CACHE_BYTES_PER_GIG * > + div64_u64(size, 1024 * 1024 * 1024); > > /* > * we want to account for 1 more bitmap than what we have so we can make > -- > 1.7.0.1 > Reviewed-by: Josef Bacik Thanks, Josef