We will sometimes start background flushing the various enospc related things (delayed nodes, delalloc, etc) if we are getting close to reserving all of our available space. We don't want to do this however when we are actually using this space as it causes unneeded thrashing. We currently try to do this by checking bytes_used >= thresh, but bytes_used is only part of the equation, we need to use bytes_reserved as well as this represents space that is very likely to become bytes_used in the future. My tracing tool will keep count of the number of times we kick off the async flusher, the following are counts for the entire run of generic/027 No Patch Patch avg: 5385 5009 median: 5500 4916 We skewed lower than the average with my patch and higher than the average with the patch, overall it cuts the flushing from anywhere from 5-10%, which in the case of actual ENOSPC is quite helpful. Thanks, Signed-off-by: Josef Bacik <jbacik@xxxxxx> --- fs/btrfs/extent-tree.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index e9ec337..63188c0 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -4849,7 +4849,7 @@ static inline int need_do_async_reclaim(struct btrfs_space_info *space_info, u64 thresh = div_factor_fine(space_info->total_bytes, 98); /* If we're just plain full then async reclaim just slows us down. */ - if (space_info->bytes_used >= thresh) + if ((space_info->bytes_used + space_info->bytes_reserved) >= thresh) return 0; return (used >= thresh && !btrfs_fs_closing(fs_info) && -- 1.8.3.1 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
