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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 12/19] btrfs: limit max discard size for async discard
Date: Thu, 10 Oct 2019 12:16:38 -0400	[thread overview]
Message-ID: <20191010161637.5tyauzyb3trb72te@macbook-pro-91.dhcp.thefacebook.com> (raw)
In-Reply-To: <7eed2e0ebdc4cc4a7e31c6fa7a180f10158fba0f.1570479299.git.dennis@kernel.org>

On Mon, Oct 07, 2019 at 04:17:43PM -0400, Dennis Zhou wrote:
> Throttle the maximum size of a discard so that we can provide an upper
> bound for the rate of async discard. While the block layer is able to
> split discards into the appropriate sized discards, we want to be able
> to account more accurately the rate at which we are consuming ncq slots
> as well as limit the upper bound of work for a discard.
> 
> Signed-off-by: Dennis Zhou <dennis@kernel.org>
> ---
>  fs/btrfs/discard.h          |  4 ++++
>  fs/btrfs/free-space-cache.c | 47 +++++++++++++++++++++++++++----------
>  2 files changed, 39 insertions(+), 12 deletions(-)
> 
> diff --git a/fs/btrfs/discard.h b/fs/btrfs/discard.h
> index acaf56f63b1c..898dd92dbf8f 100644
> --- a/fs/btrfs/discard.h
> +++ b/fs/btrfs/discard.h
> @@ -8,6 +8,7 @@
>  
>  #include <linux/kernel.h>
>  #include <linux/jiffies.h>
> +#include <linux/sizes.h>
>  #include <linux/time.h>
>  #include <linux/workqueue.h>
>  
> @@ -15,6 +16,9 @@
>  #include "block-group.h"
>  #include "free-space-cache.h"
>  
> +/* discard size limits */
> +#define BTRFS_DISCARD_MAX_SIZE		(SZ_64M)
> +

Let's make this configurable via sysfs as well.  I assume at some point in the
far, far future SSD's will stop being shitty and it would be nice to be able to
easily adjust and test.  Also this only applies to async, so
BTRFS_ASYNC_DISCARD_MAX_SIZE.  You can add a follow up patch for the sysfs
stuff, just adjust the name and you can add

Reviewed-by: Josef Bacik <josef@toxicpanda.com>

Thanks,

Josef

  reply	other threads:[~2019-10-10 16:16 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
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 [this message]
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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