From 4aa9ad520398bf9cef70fc9c363567da44312045 Mon Sep 17 00:00:00 2001 From: Dennis Zhou Date: Thu, 2 Jan 2020 16:26:37 -0500 Subject: btrfs: limit max discard size for async discard 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. Reviewed-by: Josef Bacik Signed-off-by: Dennis Zhou Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/discard.h | 5 +++++ fs/btrfs/free-space-cache.c | 41 ++++++++++++++++++++++++++++++++--------- 2 files changed, 37 insertions(+), 9 deletions(-) (limited to 'fs/btrfs') diff --git a/fs/btrfs/discard.h b/fs/btrfs/discard.h index 5250fe178e49..562c60fab77a 100644 --- a/fs/btrfs/discard.h +++ b/fs/btrfs/discard.h @@ -3,10 +3,15 @@ #ifndef BTRFS_DISCARD_H #define BTRFS_DISCARD_H +#include + struct btrfs_fs_info; struct btrfs_discard_ctl; struct btrfs_block_group; +/* Discard size limits */ +#define BTRFS_ASYNC_DISCARD_MAX_SIZE (SZ_64M) + /* Work operations */ void btrfs_discard_cancel_work(struct btrfs_discard_ctl *discard_ctl, struct btrfs_block_group *block_group); diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c index 40fb918a82f4..438043aab6fb 100644 --- a/fs/btrfs/free-space-cache.c +++ b/fs/btrfs/free-space-cache.c @@ -3466,16 +3466,36 @@ static int trim_no_bitmap(struct btrfs_block_group *block_group, extent_start = entry->offset; extent_bytes = entry->bytes; extent_trim_state = entry->trim_state; - start = max(start, extent_start); - bytes = min(extent_start + extent_bytes, end) - start; - if (bytes < minlen) { - spin_unlock(&ctl->tree_lock); - mutex_unlock(&ctl->cache_writeout_mutex); - goto next; - } + if (async) { + start = entry->offset; + bytes = entry->bytes; + if (bytes < minlen) { + spin_unlock(&ctl->tree_lock); + mutex_unlock(&ctl->cache_writeout_mutex); + goto next; + } + unlink_free_space(ctl, entry); + if (bytes > BTRFS_ASYNC_DISCARD_MAX_SIZE) { + bytes = BTRFS_ASYNC_DISCARD_MAX_SIZE; + extent_bytes = BTRFS_ASYNC_DISCARD_MAX_SIZE; + entry->offset += BTRFS_ASYNC_DISCARD_MAX_SIZE; + entry->bytes -= BTRFS_ASYNC_DISCARD_MAX_SIZE; + link_free_space(ctl, entry); + } else { + kmem_cache_free(btrfs_free_space_cachep, entry); + } + } else { + start = max(start, extent_start); + bytes = min(extent_start + extent_bytes, end) - start; + if (bytes < minlen) { + spin_unlock(&ctl->tree_lock); + mutex_unlock(&ctl->cache_writeout_mutex); + goto next; + } - unlink_free_space(ctl, entry); - kmem_cache_free(btrfs_free_space_cachep, entry); + unlink_free_space(ctl, entry); + kmem_cache_free(btrfs_free_space_cachep, entry); + } spin_unlock(&ctl->tree_lock); trim_entry.start = extent_start; @@ -3639,6 +3659,9 @@ static int trim_bitmaps(struct btrfs_block_group *block_group, goto next; } + if (async && bytes > BTRFS_ASYNC_DISCARD_MAX_SIZE) + bytes = BTRFS_ASYNC_DISCARD_MAX_SIZE; + bitmap_clear_bits(ctl, entry, start, bytes); if (entry->bytes == 0) free_bitmap(ctl, entry); -- cgit v1.2.3