From e9f59429b87d35cf23ae9ca19629bd686a1c0304 Mon Sep 17 00:00:00 2001 From: Boris Burkov Date: Wed, 5 Apr 2023 12:43:58 -0700 Subject: [PATCH 1/2] btrfs: set default discard iops_limit to 1000 Previously, the default was a relatively conservative 10. This results in a 100ms delay, so with ~300 discards in a commit, it takes the full 30s till the next commit to finish the discards. On a workstation, this results in the disk never going idle, wasting power/battery, etc. Set the default to 1000, which results in using the smallest possible delay, currently, which is 1ms. This has shown to not pathologically keep the disk busy by the original reporter. Link: https://lore.kernel.org/linux-btrfs/Y%2F+n1wS%2F4XAH7X1p@nz/ Link: https://bugzilla.redhat.com/show_bug.cgi?id=2182228 CC: stable@vger.kernel.org # 6.2+ Reviewed-by: Neal Gompa Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/discard.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/btrfs/discard.c b/fs/btrfs/discard.c index 317aeff6c1da..0bc526f5fcd9 100644 --- a/fs/btrfs/discard.c +++ b/fs/btrfs/discard.c @@ -60,7 +60,7 @@ #define BTRFS_DISCARD_TARGET_MSEC (6 * 60 * 60UL * MSEC_PER_SEC) #define BTRFS_DISCARD_MIN_DELAY_MSEC (1UL) #define BTRFS_DISCARD_MAX_DELAY_MSEC (1000UL) -#define BTRFS_DISCARD_MAX_IOPS (10U) +#define BTRFS_DISCARD_MAX_IOPS (1000U) /* Monotonically decreasing minimum length filters after index 0 */ static int discard_minlen[BTRFS_NR_DISCARD_LISTS] = { From ef9cddfe57d86aac6b509b550136395669159b30 Mon Sep 17 00:00:00 2001 From: Boris Burkov Date: Wed, 5 Apr 2023 12:43:59 -0700 Subject: [PATCH 2/2] btrfs: reinterpret async discard iops_limit=0 as no delay Currently, a limit of 0 results in a hard coded metering over 6 hours. Since the default is a set limit, I suspect no one truly depends on this rather arbitrary setting. Repurpose it for an arguably more useful "unlimited" mode, where the delay is 0. Note that if block groups are too new, or go fully empty, there is still a delay associated with those conditions. Those delays implement heuristics for not trimming a region we are relatively likely to fully overwrite soon. CC: stable@vger.kernel.org # 6.2+ Reviewed-by: Neal Gompa Signed-off-by: Boris Burkov Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/discard.c | 21 +++++++++++++-------- 1 file changed, 13 insertions(+), 8 deletions(-) diff --git a/fs/btrfs/discard.c b/fs/btrfs/discard.c index 0bc526f5fcd9..a6d77fe41e1a 100644 --- a/fs/btrfs/discard.c +++ b/fs/btrfs/discard.c @@ -56,8 +56,6 @@ #define BTRFS_DISCARD_DELAY (120ULL * NSEC_PER_SEC) #define BTRFS_DISCARD_UNUSED_DELAY (10ULL * NSEC_PER_SEC) -/* Target completion latency of discarding all discardable extents */ -#define BTRFS_DISCARD_TARGET_MSEC (6 * 60 * 60UL * MSEC_PER_SEC) #define BTRFS_DISCARD_MIN_DELAY_MSEC (1UL) #define BTRFS_DISCARD_MAX_DELAY_MSEC (1000UL) #define BTRFS_DISCARD_MAX_IOPS (1000U) @@ -577,6 +575,7 @@ void btrfs_discard_calc_delay(struct btrfs_discard_ctl *discard_ctl) s32 discardable_extents; s64 discardable_bytes; u32 iops_limit; + unsigned long min_delay = BTRFS_DISCARD_MIN_DELAY_MSEC; unsigned long delay; discardable_extents = atomic_read(&discard_ctl->discardable_extents); @@ -607,13 +606,19 @@ void btrfs_discard_calc_delay(struct btrfs_discard_ctl *discard_ctl) } iops_limit = READ_ONCE(discard_ctl->iops_limit); - if (iops_limit) - delay = MSEC_PER_SEC / iops_limit; - else - delay = BTRFS_DISCARD_TARGET_MSEC / discardable_extents; - delay = clamp(delay, BTRFS_DISCARD_MIN_DELAY_MSEC, - BTRFS_DISCARD_MAX_DELAY_MSEC); + if (iops_limit) { + delay = MSEC_PER_SEC / iops_limit; + } else { + /* + * Unset iops_limit means go as fast as possible, so allow a + * delay of 0. + */ + delay = 0; + min_delay = 0; + } + + delay = clamp(delay, min_delay, BTRFS_DISCARD_MAX_DELAY_MSEC); discard_ctl->delay_ms = delay; spin_unlock(&discard_ctl->lock);