@@ -1401,6 +1401,17 @@ int journal_stop(handle_t *handle)
* on IO anyway. Speeds up many-threaded, many-dir operations
* by 30x or more...
*
+ * We try and optimize the sleep time against what the underlying disk
+ * can do, instead of having a static sleep time. This is usefull for
+ * the case where our storage is so fast that it is more optimal to go
+ * ahead and force a flush and wait for the transaction to be committed
+ * than it is to wait for an arbitrary amount of time for new writers to
+ * join the transaction. We acheive this by measuring how long it takes
+ * to commit a transaction, and compare it with how long this
+ * transaction has been running, and if run time < commit time then we
+ * sleep for the delta and commit. This greatly helps super fast disks
+ * that would see slowdowns as more threads started doing fsyncs.
+ *
* But don't do this if this process was the most recent one to
* perform a synchronous write. We do this to detect the case where a
* single process is doing a stream of sync writes. No point in waiting
@@ -803,8 +803,16 @@ struct journal_s
struct buffer_head **j_wbuf;
int j_wbufsize;
+ /*
+ * this is the pid of the last person to run a synchronous operation
+ * through the journal.
+ */
pid_t j_last_sync_writer;
+ /*
+ * the average amount of time in nanoseconds it takes to commit a
+ * transaction to the disk. [j_state_lock]
+ */
u64 j_average_commit_time;
/*
The patch titled improve jbd fsync batching (update) has been added to the -mm tree. Its filename is jbd-improve-fsync-batching-update.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find out what to do about this The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: improve jbd fsync batching (update) From: Josef Bacik <jbacik@redhat.com> On Mon, Nov 03, 2008 at 12:55:09PM -0800, Andrew Morton wrote: > On Mon, 3 Nov 2008 15:24:43 -0500 > Josef Bacik <jbacik@redhat.com> wrote: > > > > please fix. > > > > I see you already pulled this into -mm, would you like me to repost with the > > same changelog and the patch updated, or just reply to this with the updated > > patch? Thanks, > > Either works for me at this stage. If it's a replacement then I'll turn > it into an incremental so I can see what changed, which takes me about 2.15 > seconds. > > If it had been a large patch or if it had been under test in someone's > tree for a while then a replacement patch would be unwelcome. But for a > small, fresh patch like this one it's no big deal either way. > Ok here is a replacement patch with the comments as requested, as well as a comment for j_last_sync_writer. Thank you, Cc: Andreas Dilger <adilger@sun.com> Cc: Arjan van de Ven <arjan@infradead.org> Cc: Ric Wheeler <rwheeler@redhat.com> Cc: <linux-ext4@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> --- fs/jbd/transaction.c | 11 +++++++++++ include/linux/jbd.h | 8 ++++++++ 2 files changed, 19 insertions(+)