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 <jbacik@xxxxxxxxxx>
---
fs/btrfs/ctree.h | 2 ++
fs/btrfs/tree-log.c | 12 +++++++++++-
2 files changed, 13 insertions(+), 1 deletions(-)
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 2aeb3a8..f77935e 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1001,6 +1001,8 @@ 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 f4a7b62..a38f6f3 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
--
1.5.4.3
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