From: Josef Bacik <josef@toxicpanda.com>
To: Dennis Zhou <dennis@kernel.org>
Cc: 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 08/19] btrfs: track discardable extents for asnyc discard
Date: Thu, 10 Oct 2019 11:36:54 -0400 [thread overview]
Message-ID: <20191010153653.7b26qpleh64dext3@macbook-pro-91.dhcp.thefacebook.com> (raw)
In-Reply-To: <31c4f29228c76df72cc92112e397db648e9b9ab9.1570479299.git.dennis@kernel.org>
On Mon, Oct 07, 2019 at 04:17:39PM -0400, Dennis Zhou wrote:
> The number of discardable extents will serve as the rate limiting metric
> for how often we should discard. This keeps track of discardable extents
> in the free space caches by maintaining deltas and propagating them to
> the global count.
>
> This also setups up a discard directory in btrfs sysfs and exports the
> total discard_extents count.
>
> Signed-off-by: Dennis Zhou <dennis@kernel.org>
> ---
> fs/btrfs/ctree.h | 2 +
> fs/btrfs/discard.c | 2 +
> fs/btrfs/discard.h | 19 ++++++++
> fs/btrfs/free-space-cache.c | 93 ++++++++++++++++++++++++++++++++++---
> fs/btrfs/free-space-cache.h | 2 +
> fs/btrfs/sysfs.c | 33 +++++++++++++
> 6 files changed, 144 insertions(+), 7 deletions(-)
>
> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> index c328d2e85e4d..43e515939b9c 100644
> --- a/fs/btrfs/ctree.h
> +++ b/fs/btrfs/ctree.h
> @@ -447,6 +447,7 @@ struct btrfs_discard_ctl {
> spinlock_t lock;
> struct btrfs_block_group_cache *cache;
> struct list_head discard_list[BTRFS_NR_DISCARD_LISTS];
> + atomic_t discard_extents;
> };
>
> /* delayed seq elem */
> @@ -831,6 +832,7 @@ struct btrfs_fs_info {
> struct btrfs_workqueue *scrub_wr_completion_workers;
> struct btrfs_workqueue *scrub_parity_workers;
>
> + struct kobject *discard_kobj;
> struct btrfs_discard_ctl discard_ctl;
>
> #ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
> diff --git a/fs/btrfs/discard.c b/fs/btrfs/discard.c
> index 26a1e44b4bfa..0544eb6717d4 100644
> --- a/fs/btrfs/discard.c
> +++ b/fs/btrfs/discard.c
> @@ -298,6 +298,8 @@ void btrfs_discard_init(struct btrfs_fs_info *fs_info)
>
> for (i = 0; i < BTRFS_NR_DISCARD_LISTS; i++)
> INIT_LIST_HEAD(&discard_ctl->discard_list[i]);
> +
> + atomic_set(&discard_ctl->discard_extents, 0);
> }
>
> void btrfs_discard_cleanup(struct btrfs_fs_info *fs_info)
> diff --git a/fs/btrfs/discard.h b/fs/btrfs/discard.h
> index 22cfa7e401bb..85939d62521e 100644
> --- a/fs/btrfs/discard.h
> +++ b/fs/btrfs/discard.h
> @@ -71,4 +71,23 @@ void btrfs_discard_queue_work(struct btrfs_discard_ctl *discard_ctl,
> btrfs_discard_schedule_work(discard_ctl, false);
> }
>
> +static inline
> +void btrfs_discard_update_discardable(struct btrfs_block_group_cache *cache,
> + struct btrfs_free_space_ctl *ctl)
> +{
> + struct btrfs_discard_ctl *discard_ctl;
> + s32 extents_delta;
> +
> + if (!cache || !btrfs_test_opt(cache->fs_info, DISCARD_ASYNC))
> + return;
> +
> + discard_ctl = &cache->fs_info->discard_ctl;
> +
> + extents_delta = ctl->discard_extents[0] - ctl->discard_extents[1];
> + if (extents_delta) {
> + atomic_add(extents_delta, &discard_ctl->discard_extents);
> + ctl->discard_extents[1] = ctl->discard_extents[0];
> + }
What the actual fuck? I assume you did this to avoid checking DISCARD_ASYNC on
every update, but man this complexity is not worth it. We might as well update
the counter every time to avoid doing stuff like this.
If there's a better reason for doing it this way then I'm all ears, but even so
this is not the way to do it. Just do
atomic_add(ctl->discard_extenst, &discard_ctl->discard_extents);
ctl->discard_extents = 0;
and avoid the two step thing. And a comment, because it was like 5 minutes
between me seeing this and getting to your reasoning, and in between there was a
lot of swearing. Thanks,
Josef
next prev parent reply other threads:[~2019-10-10 15:36 UTC|newest]
Thread overview: 71+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-07 20:17 [RFC PATCH 00/19] btrfs: async discard support Dennis Zhou
2019-10-07 20:17 ` [PATCH 01/19] bitmap: genericize percpu bitmap region iterators Dennis Zhou
2019-10-07 20:26 ` Josef Bacik
2019-10-07 22:24 ` Dennis Zhou
2019-10-15 12:11 ` David Sterba
2019-10-15 18:35 ` Dennis Zhou
2019-10-07 20:17 ` [PATCH 02/19] btrfs: rename DISCARD opt to DISCARD_SYNC Dennis Zhou
2019-10-07 20:27 ` Josef Bacik
2019-10-08 11:12 ` Johannes Thumshirn
2019-10-11 9:19 ` Nikolay Borisov
2019-10-07 20:17 ` [PATCH 03/19] btrfs: keep track of which extents have been discarded Dennis Zhou
2019-10-07 20:37 ` Josef Bacik
2019-10-07 22:38 ` Dennis Zhou
2019-10-10 13:40 ` Josef Bacik
2019-10-11 16:15 ` Dennis Zhou
2019-10-08 12:46 ` Nikolay Borisov
2019-10-11 16:08 ` Dennis Zhou
2019-10-15 12:17 ` David Sterba
2019-10-15 19:58 ` Dennis Zhou
2019-10-07 20:17 ` [PATCH 04/19] btrfs: keep track of cleanliness of the bitmap Dennis Zhou
2019-10-10 14:16 ` Josef Bacik
2019-10-11 16:17 ` Dennis Zhou
2019-10-15 12:23 ` David Sterba
2019-10-07 20:17 ` [PATCH 05/19] btrfs: add the beginning of async discard, discard workqueue Dennis Zhou
2019-10-10 14:38 ` Josef Bacik
2019-10-15 12:49 ` David Sterba
2019-10-15 19:57 ` Dennis Zhou
2019-10-07 20:17 ` [PATCH 06/19] btrfs: handle empty block_group removal Dennis Zhou
2019-10-10 15:00 ` Josef Bacik
2019-10-11 16:52 ` Dennis Zhou
2019-10-07 20:17 ` [PATCH 07/19] btrfs: discard one region at a time in async discard Dennis Zhou
2019-10-10 15:22 ` Josef Bacik
2019-10-14 19:42 ` Dennis Zhou
2019-10-07 20:17 ` [PATCH 08/19] btrfs: track discardable extents for asnyc discard Dennis Zhou
2019-10-10 15:36 ` Josef Bacik [this message]
2019-10-14 19:50 ` Dennis Zhou
2019-10-15 13:12 ` David Sterba
2019-10-15 18:41 ` Dennis Zhou
2019-10-07 20:17 ` [PATCH 09/19] btrfs: keep track of discardable_bytes Dennis Zhou
2019-10-10 15:38 ` Josef Bacik
2019-10-07 20:17 ` [PATCH 10/19] btrfs: calculate discard delay based on number of extents Dennis Zhou
2019-10-10 15:41 ` Josef Bacik
2019-10-11 18:07 ` Dennis Zhou
2019-10-07 20:17 ` [PATCH 11/19] btrfs: add bps discard rate limit Dennis Zhou
2019-10-10 15:47 ` Josef Bacik
2019-10-14 19:56 ` Dennis Zhou
2019-10-07 20:17 ` [PATCH 12/19] btrfs: limit max discard size for async discard Dennis Zhou
2019-10-10 16:16 ` Josef Bacik
2019-10-14 19:57 ` Dennis Zhou
2019-10-07 20:17 ` [PATCH 13/19] btrfs: have multiple discard lists Dennis Zhou
2019-10-10 16:51 ` Josef Bacik
2019-10-14 20:04 ` Dennis Zhou
2019-10-07 20:17 ` [PATCH 14/19] btrfs: only keep track of data extents for async discard Dennis Zhou
2019-10-10 16:53 ` Josef Bacik
2019-10-07 20:17 ` [PATCH 15/19] btrfs: load block_groups into discard_list on mount Dennis Zhou
2019-10-10 17:11 ` Josef Bacik
2019-10-14 20:17 ` Dennis Zhou
2019-10-14 23:38 ` David Sterba
2019-10-15 15:42 ` Dennis Zhou
2019-10-07 20:17 ` [PATCH 16/19] btrfs: keep track of discard reuse stats Dennis Zhou
2019-10-10 17:13 ` Josef Bacik
2019-10-07 20:17 ` [PATCH 17/19] btrfs: add async discard header Dennis Zhou
2019-10-10 17:13 ` Josef Bacik
2019-10-07 20:17 ` [PATCH 18/19] btrfs: increase the metadata allowance for the free_space_cache Dennis Zhou
2019-10-10 17:16 ` Josef Bacik
2019-10-07 20:17 ` [PATCH 19/19] btrfs: make smaller extents more likely to go into bitmaps Dennis Zhou
2019-10-10 17:17 ` Josef Bacik
2019-10-11 7:49 ` [RFC PATCH 00/19] btrfs: async discard support Nikolay Borisov
2019-10-14 21:05 ` Dennis Zhou
2019-10-15 12:08 ` David Sterba
2019-10-15 15:41 ` Dennis Zhou
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