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From: Dennis Zhou <dennis@kernel.org>
To: dsterba@suse.cz, David Sterba <dsterba@suse.com>,
	Chris Mason <clm@fb.com>, Josef Bacik <josef@toxicpanda.com>,
	Omar Sandoval <osandov@osandov.com>,
	kernel-team@fb.com, linux-btrfs@vger.kernel.org
Subject: Re: [PATCH 18/22] btrfs: only keep track of data extents for async discard
Date: Thu, 2 Jan 2020 11:55:59 -0500
Message-ID: <20200102165559.GE86832@dennisz-mbp.dhcp.thefacebook.com> (raw)
In-Reply-To: <20191230173954.GX3929@twin.jikos.cz>

On Mon, Dec 30, 2019 at 06:39:54PM +0100, David Sterba wrote:
> On Fri, Dec 13, 2019 at 04:22:27PM -0800, Dennis Zhou wrote:
> > As mentioned earlier, discarding data can be done either by issuing an
> > explicit discard or implicitly by reusing the LBA. Metadata chunks see
> > much more frequent reuse due to well it being metadata. So instead of
> > explicitly discarding metadata blocks, just leave them be and let the
> > latter implicit discarding be done for them.
> > 
> > Signed-off-by: Dennis Zhou <dennis@kernel.org>
> > Reviewed-by: Josef Bacik <josef@toxicpanda.com>
> > ---
> >  fs/btrfs/block-group.h |  6 ++++++
> >  fs/btrfs/discard.c     | 11 +++++++++--
> >  2 files changed, 15 insertions(+), 2 deletions(-)
> > 
> > diff --git a/fs/btrfs/block-group.h b/fs/btrfs/block-group.h
> > index 601e1d217e22..ee8441439a56 100644
> > --- a/fs/btrfs/block-group.h
> > +++ b/fs/btrfs/block-group.h
> > @@ -182,6 +182,12 @@ static inline u64 btrfs_block_group_end(struct btrfs_block_group *block_group)
> >  	return (block_group->start + block_group->length);
> >  }
> >  
> > +static inline bool btrfs_is_block_group_data(
> > +					struct btrfs_block_group *block_group)
> > +{
> > +	return (block_group->flags & BTRFS_BLOCK_GROUP_DATA);
> 
> What happens for mixed data and metadata block groups? As this is a
> special mode that will likely lead to fragmented block groups I think
> that async discard won't be able to help much.
> 
> I'd suggest to make the test explicit only for the separate block group
> types and comment that mixed bg's are not supported.

Yeah it probably wouldn't do the system much good. I've renamed the test
to btrfs_is_block_group_data_only() and added a comment in the async
discard header patch to state that mixed block_groups aren't supported.

  reply index

Thread overview: 56+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-14  0:22 [PATCH v6 00/22] btrfs: async discard support Dennis Zhou
2019-12-14  0:22 ` [PATCH 01/22] bitmap: genericize percpu bitmap region iterators Dennis Zhou
2019-12-14  0:22 ` [PATCH 02/22] btrfs: rename DISCARD opt to DISCARD_SYNC Dennis Zhou
2019-12-14  0:22 ` [PATCH 03/22] btrfs: keep track of which extents have been discarded Dennis Zhou
2019-12-14  0:22 ` [PATCH 04/22] btrfs: keep track of cleanliness of the bitmap Dennis Zhou
2019-12-14  0:22 ` [PATCH 05/22] btrfs: add the beginning of async discard, discard workqueue Dennis Zhou
2019-12-14  0:22 ` [PATCH 06/22] btrfs: handle empty block_group removal Dennis Zhou
2019-12-14  0:22 ` [PATCH 07/22] btrfs: discard one region at a time in async discard Dennis Zhou
2019-12-14  0:22 ` [PATCH 08/22] btrfs: add removal calls for sysfs debug/ Dennis Zhou
2019-12-18 11:45   ` Anand Jain
2019-12-14  0:22 ` [PATCH 09/22] btrfs: make UUID/debug have its own kobject Dennis Zhou
2019-12-18 11:45   ` Anand Jain
2019-12-14  0:22 ` [PATCH 10/22] btrfs: add discard sysfs directory Dennis Zhou
2019-12-18 11:45   ` Anand Jain
2019-12-14  0:22 ` [PATCH 11/22] btrfs: track discardable extents for async discard Dennis Zhou
2019-12-14  0:22 ` [PATCH 12/22] btrfs: keep track of discardable_bytes Dennis Zhou
2019-12-14  0:22 ` [PATCH 13/22] btrfs: calculate discard delay based on number of extents Dennis Zhou
2019-12-30 16:50   ` David Sterba
2020-01-02 16:45     ` Dennis Zhou
2019-12-14  0:22 ` [PATCH 14/22] btrfs: add bps discard rate limit Dennis Zhou
2019-12-30 17:58   ` David Sterba
2020-01-02 16:46     ` Dennis Zhou
2019-12-14  0:22 ` [PATCH 15/22] btrfs: limit max discard size for async discard Dennis Zhou
2019-12-30 18:00   ` David Sterba
2019-12-30 18:08   ` David Sterba
2020-01-02 16:48     ` Dennis Zhou
2019-12-14  0:22 ` [PATCH 16/22] btrfs: make max async discard size tunable Dennis Zhou
2019-12-30 18:05   ` David Sterba
2020-01-02 16:50     ` Dennis Zhou
2019-12-14  0:22 ` [PATCH 17/22] btrfs: have multiple discard lists Dennis Zhou
2019-12-14  0:22 ` [PATCH 18/22] btrfs: only keep track of data extents for async discard Dennis Zhou
2019-12-30 17:39   ` David Sterba
2020-01-02 16:55     ` Dennis Zhou [this message]
2019-12-14  0:22 ` [PATCH 19/22] btrfs: keep track of discard reuse stats Dennis Zhou
2019-12-30 17:33   ` David Sterba
2020-01-02 16:57     ` Dennis Zhou
2019-12-14  0:22 ` [PATCH 20/22] btrfs: add async discard header Dennis Zhou
2019-12-14  0:22 ` [PATCH 21/22] btrfs: increase the metadata allowance for the free_space_cache Dennis Zhou
2019-12-14  0:22 ` [PATCH 22/22] btrfs: make smaller extents more likely to go into bitmaps Dennis Zhou
2019-12-17 14:55 ` [PATCH v6 00/22] btrfs: async discard support David Sterba
2019-12-18  0:06   ` Dennis Zhou
2019-12-19  2:03     ` Dennis Zhou
2019-12-19 20:06       ` David Sterba
2019-12-19 21:22         ` Dennis Zhou
2019-12-19 20:34     ` David Sterba
2019-12-19 21:17       ` Dennis Zhou
2019-12-30 18:13 ` David Sterba
2019-12-30 18:49   ` Dennis Zhou
2020-01-02 13:22     ` David Sterba
  -- strict thread matches above, loose matches on Subject: below --
2019-12-09 19:45 [PATCH v5 " Dennis Zhou
2019-12-09 19:46 ` [PATCH 18/22] btrfs: only keep track of data extents for async discard Dennis Zhou
2019-11-25 19:46 [PATCH v4 00/22] btrfs: async discard support Dennis Zhou
2019-11-25 19:46 ` [PATCH 18/22] btrfs: only keep track of data extents for async discard Dennis Zhou
2019-11-20 21:50 [PATCH v3 00/22] btrfs: async discard support Dennis Zhou
2019-11-20 21:51 ` [PATCH 18/22] btrfs: only keep track of data extents for async discard Dennis Zhou
2019-10-23 22:52 [PATCH v2 00/22] btrfs: async discard support Dennis Zhou
2019-10-23 22:53 ` [PATCH 18/22] btrfs: only keep track of data extents for async discard Dennis Zhou
2019-11-08 19:46   ` Josef Bacik
2019-11-08 20:14     ` Dennis Zhou
2019-11-15 17:31       ` David Sterba

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