On Wed, 8 Aug 2007 17:29:22 -0400
Josef Bacik <[EMAIL PROTECTED]> wrote:
> Hello,
>
> Ok so now with this patch we're walloping ext3. ext3 was getting
> about 35 files/sec, whereas btrfs was getting 25 files/sec. With
> this change btrfs gets around 170 files/sec. I yanked out the writer
> waitqueue as it was causing a hang b/c we wouldn't wake up.
The waitqueue part made a big difference for reiserfs in multi-threaded
workloads, lets try to keep it. I think the reason you're missing
wakeups is because you always wait, even when there's no one else
around. If you used a schedule_timeout in the case where the number of
writers was zero, it should all work out.
> The only
> thing thats weird about this, and I think this is in part because of
> fs_mutex, is that we _never_ get anybody add anything to the
> transaction. I put debug statements in the do/while loop to see if
> we ever loop, and we don't, however we manage to push alot more
> through so I'm kind of confused, so if anybody has any ideas I'd love
> to hear them. Thanks much,
Now that is confusing because the fs_mutex gets dropped during the
wait. btrfs_transaction_cleaner should be hopping in every 5 seconds
or so, could you please toss in some printks there? It would be the
only other writer in a single threaded fs_mark run.
-chris
>
> Josef
>
> diff -r 1765acb6d268 transaction.c
> --- a/transaction.c Tue Aug 07 16:35:25 2007 -0400
> +++ b/transaction.c Wed Aug 08 17:29:58 2007 -0400
> @@ -56,8 +56,8 @@ static int join_transaction(struct btrfs
> root->fs_info->generation++;
> root->fs_info->running_transaction = cur_trans;
> cur_trans->num_writers = 0;
> + cur_trans->writers_while_asleep = 0;
> cur_trans->transid = root->fs_info->generation;
> - init_waitqueue_head(&cur_trans->writer_wait);
> init_waitqueue_head(&cur_trans->commit_wait);
> cur_trans->in_commit = 0;
> cur_trans->use_count = 1;
> @@ -67,6 +67,7 @@ static int join_transaction(struct btrfs
> init_bit_radix(&cur_trans->dirty_pages);
> }
> cur_trans->num_writers++;
> + cur_trans->writers_while_asleep++;
> return 0;
> }
>
> @@ -124,8 +125,6 @@ int btrfs_end_transaction(struct btrfs_t
> WARN_ON(cur_trans != trans->transaction);
> WARN_ON(cur_trans->num_writers < 1);
> cur_trans->num_writers--;
> - if (waitqueue_active(&cur_trans->writer_wait))
> - wake_up(&cur_trans->writer_wait);
> put_transaction(cur_trans);
> mutex_unlock(&root->fs_info->trans_mutex);
> memset(trans, 0, sizeof(*trans));
> @@ -212,6 +211,7 @@ static int wait_for_commit(struct btrfs_
> struct btrfs_transaction *commit)
> {
> DEFINE_WAIT(wait);
> +
> mutex_lock(&root->fs_info->trans_mutex);
> while(!commit->commit_done) {
> prepare_to_wait(&commit->commit_wait, &wait,
> @@ -413,12 +413,11 @@ int btrfs_commit_transaction(struct btrf
> int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
> struct btrfs_root *root)
> {
> - int ret = 0;
> + int ret = 0, writers = 0;
> struct btrfs_transaction *cur_trans;
> struct btrfs_transaction *prev_trans = NULL;
> struct list_head dirty_fs_roots;
> struct radix_tree_root pinned_copy;
> - DEFINE_WAIT(wait);
>
> init_bit_radix(&pinned_copy);
> INIT_LIST_HEAD(&dirty_fs_roots);
> @@ -454,20 +453,19 @@ int btrfs_commit_transaction(struct btrf
> mutex_lock(&root->fs_info->trans_mutex);
> }
> }
> - while (trans->transaction->num_writers > 1) {
> + do{
> + writers = trans->transaction->writers_while_asleep;
> WARN_ON(cur_trans != trans->transaction);
> - prepare_to_wait(&trans->transaction->writer_wait,
> &wait,
> - TASK_UNINTERRUPTIBLE);
> - if (trans->transaction->num_writers <= 1)
> - break;
> mutex_unlock(&root->fs_info->fs_mutex);
> mutex_unlock(&root->fs_info->trans_mutex);
> - schedule();
> +
> + schedule_timeout_uninterruptible(1);
> +
> mutex_lock(&root->fs_info->fs_mutex);
> mutex_lock(&root->fs_info->trans_mutex);
> - finish_wait(&trans->transaction->writer_wait, &wait);
> - }
> - finish_wait(&trans->transaction->writer_wait, &wait);
> + } while (trans->transaction->num_writers > 1 ||
> + writers !=
> trans->transaction->writers_while_asleep); +
> WARN_ON(cur_trans != trans->transaction);
> ret = add_dirty_roots(trans, &root->fs_info->fs_roots_radix,
> &dirty_fs_roots);
> diff -r 1765acb6d268 transaction.h
> --- a/transaction.h Tue Aug 07 16:35:25 2007 -0400
> +++ b/transaction.h Wed Aug 08 17:10:51 2007 -0400
> @@ -26,10 +26,10 @@ struct btrfs_transaction {
> int in_commit;
> int use_count;
> int commit_done;
> + unsigned long writers_while_asleep;
> struct list_head list;
> struct radix_tree_root dirty_pages;
> unsigned long start_time;
> - wait_queue_head_t writer_wait;
> wait_queue_head_t commit_wait;
> };
>
>
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