From ff782e0a131c7f669445c07fe5c7ba91e043b7ed Mon Sep 17 00:00:00 2001 From: Josef Bacik Date: Thu, 8 Oct 2009 15:30:04 -0400 Subject: [PATCH] Btrfs: optimize fsync for the single writer case This patch optimizes the tree logging stuff so it doesn't always wait 1 jiffie for new people to join the logging transaction if there is only ever 1 writer. This helps a little bit with latency where we have something like RPM where it will fdatasync every file it writes, and so waiting the 1 jiffie for every fdatasync really starts to add up. Signed-off-by: Josef Bacik Signed-off-by: Chris Mason --- fs/btrfs/ctree.h | 2 ++ fs/btrfs/tree-log.c | 12 +++++++++++- 2 files changed, 13 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index a362dd6..16ddb19 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -1010,6 +1010,8 @@ struct btrfs_root { atomic_t log_commit[2]; unsigned long log_transid; unsigned long log_batch; + pid_t log_start_pid; + bool log_multiple_pids; u64 objectid; u64 last_trans; diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c index 4d7d9ab..78f6254 100644 --- a/fs/btrfs/tree-log.c +++ b/fs/btrfs/tree-log.c @@ -137,11 +137,20 @@ static int start_log_trans(struct btrfs_trans_handle *trans, mutex_lock(&root->log_mutex); if (root->log_root) { + if (!root->log_start_pid) { + root->log_start_pid = current->pid; + root->log_multiple_pids = false; + } else if (root->log_start_pid != current->pid) { + root->log_multiple_pids = true; + } + root->log_batch++; atomic_inc(&root->log_writers); mutex_unlock(&root->log_mutex); return 0; } + root->log_multiple_pids = false; + root->log_start_pid = current->pid; mutex_lock(&root->fs_info->tree_log_mutex); if (!root->fs_info->log_root_tree) { ret = btrfs_init_log_root_tree(trans, root->fs_info); @@ -1985,7 +1994,7 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans, if (atomic_read(&root->log_commit[(index1 + 1) % 2])) wait_log_commit(trans, root, root->log_transid - 1); - while (1) { + while (root->log_multiple_pids) { unsigned long batch = root->log_batch; mutex_unlock(&root->log_mutex); schedule_timeout_uninterruptible(1); @@ -2011,6 +2020,7 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans, root->log_batch = 0; root->log_transid++; log->log_transid = root->log_transid; + root->log_start_pid = 0; smp_mb(); /* * log tree has been flushed to disk, new modifications of -- 1.8.2.3