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List:       linux-btrfs
Subject:    Re: [PATCH 14/22] btrfs: add bps discard rate limit
From:       David Sterba <dsterba () suse ! cz>
Date:       2019-12-30 17:58:47
Message-ID: 20191230175846.GY3929 () twin ! jikos ! cz
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On Fri, Dec 13, 2019 at 04:22:23PM -0800, Dennis Zhou wrote:
> Provide an ability to rate limit based on mbps in addition to the iops
> delay calculated from number of discardable extents.
> 
> Signed-off-by: Dennis Zhou <dennis@kernel.org>
> ---
>  fs/btrfs/ctree.h   |  2 ++
>  fs/btrfs/discard.c | 18 ++++++++++++++++++
>  fs/btrfs/sysfs.c   | 31 +++++++++++++++++++++++++++++++
>  3 files changed, 51 insertions(+)
> 
> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> index 98979566e281..1b2dae5962de 100644
> --- a/fs/btrfs/ctree.h
> +++ b/fs/btrfs/ctree.h
> @@ -467,10 +467,12 @@ struct btrfs_discard_ctl {
>  	spinlock_t lock;
>  	struct btrfs_block_group *block_group;
>  	struct list_head discard_list[BTRFS_NR_DISCARD_LISTS];
> +	u64 prev_discard;
>  	atomic_t discardable_extents;
>  	atomic64_t discardable_bytes;
>  	u32 delay;
>  	u32 iops_limit;
> +	u64 bps_limit;

I think this could be u32, which makes it 4G per second. Byte
granularity is IMO not necessary so it could be KiB/sec instead and it
would be future safe with maximum limit of 4TiB/sec.
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