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Date: Tue, 15 Jul 2008 14:39:04 -0400
From: Josef Bacik <jbacik@...hat.com>
To: Ric Wheeler <ricwheeler@...il.com>
Cc: linux-ext4@...r.kernel.org, adilger@....com
Subject: Re: transaction batching performance & multi-threaded synchronous
writers
On Mon, Jul 14, 2008 at 12:15:23PM -0400, Ric Wheeler wrote:
>
> Here is a pointer to the older patch & some results:
>
> http://www.spinics.net/lists/linux-fsdevel/msg13121.html
>
> I will retry this on some updated kernels, but would not expect to see a
> difference since the code has not been changed ;-)
>
Ok here are the numbers with the original idea I had proposed.
type threads base patch speedup
sata 1 17.9 17.3 0.97
sata 2 33.2 34.2 1.03
sata 4 58.4 63.6 1.09
sata 8 78.8 80.8 1.03
sata 16 94.4 97.6 1.16
ram 1 2394.4 1878.0 0.78
ram 2 989.6 2041.1 2.06
ram 4 1466.1 3201.8 2.18
ram 8 1858.1 3362.8 1.81
ram 16 3008.0 3227.7 1.07
I've got to find a fast disk array to test this with, but the ramdisk results
make me happy, though they were kind of irratic, so I think the fast disk array
will be a more stable measure of how well this patch does, but it definitely
doesn't hurt the slow case, and brings stability to the fast case. Thanks much,
Josef
Index: linux-2.6/fs/jbd/commit.c
===================================================================
--- linux-2.6.orig/fs/jbd/commit.c
+++ linux-2.6/fs/jbd/commit.c
@@ -273,6 +273,15 @@ write_out_data:
journal_do_submit_data(wbuf, bufs);
}
+static inline unsigned long elapsed_jiffies(unsigned long start,
+ unsigned long end)
+{
+ if (end >= start)
+ return end - start;
+
+ return end + (MAX_JIFFY_OFFSET - start) + 1;
+}
+
/*
* journal_commit_transaction
*
@@ -288,6 +297,7 @@ void journal_commit_transaction(journal_
int flags;
int err;
unsigned long blocknr;
+ unsigned long long commit_time, start_time;
char *tagp = NULL;
journal_header_t *header;
journal_block_tag_t *tag = NULL;
@@ -400,6 +410,7 @@ void journal_commit_transaction(journal_
commit_transaction->t_state = T_FLUSH;
journal->j_committing_transaction = commit_transaction;
journal->j_running_transaction = NULL;
+ start_time = jiffies;
commit_transaction->t_log_start = journal->j_head;
wake_up(&journal->j_wait_transaction_locked);
spin_unlock(&journal->j_state_lock);
@@ -873,6 +884,12 @@ restart_loop:
J_ASSERT(commit_transaction == journal->j_committing_transaction);
journal->j_commit_sequence = commit_transaction->t_tid;
journal->j_committing_transaction = NULL;
+ commit_time = elapsed_jiffies(start_time, jiffies);
+ if (unlikely(!journal->j_average_commit_time))
+ journal->j_average_commit_time = commit_time;
+ else
+ journal->j_average_commit_time = (commit_time +
+ journal->j_average_commit_time) / 2;
spin_unlock(&journal->j_state_lock);
if (commit_transaction->t_checkpoint_list == NULL &&
Index: linux-2.6/fs/jbd/transaction.c
===================================================================
--- linux-2.6.orig/fs/jbd/transaction.c
+++ linux-2.6/fs/jbd/transaction.c
@@ -49,6 +49,7 @@ get_transaction(journal_t *journal, tran
{
transaction->t_journal = journal;
transaction->t_state = T_RUNNING;
+ transaction->t_start_time = jiffies;
transaction->t_tid = journal->j_transaction_sequence++;
transaction->t_expires = jiffies + journal->j_commit_interval;
spin_lock_init(&transaction->t_handle_lock);
@@ -1361,8 +1362,7 @@ int journal_stop(handle_t *handle)
{
transaction_t *transaction = handle->h_transaction;
journal_t *journal = transaction->t_journal;
- int old_handle_count, err;
- pid_t pid;
+ int err;
J_ASSERT(journal_current_handle() == handle);
@@ -1395,13 +1395,17 @@ int journal_stop(handle_t *handle)
* single process is doing a stream of sync writes. No point in waiting
* for joiners in that case.
*/
- pid = current->pid;
- if (handle->h_sync && journal->j_last_sync_writer != pid) {
- journal->j_last_sync_writer = pid;
- do {
- old_handle_count = transaction->t_handle_count;
+ if (handle->h_sync) {
+ unsigned long commit_time;
+
+ spin_lock(&journal->j_state_lock);
+ commit_time = journal->j_average_commit_time;
+ spin_unlock(&journal->j_state_lock);
+
+ while (time_before(jiffies, commit_time +
+ transaction->t_start_time)) {
schedule_timeout_uninterruptible(1);
- } while (old_handle_count != transaction->t_handle_count);
+ }
}
current->journal_info = NULL;
Index: linux-2.6/include/linux/jbd.h
===================================================================
--- linux-2.6.orig/include/linux/jbd.h
+++ linux-2.6/include/linux/jbd.h
@@ -543,6 +543,11 @@ struct transaction_s
unsigned long t_expires;
/*
+ * When this transaction started, in jiffies [no locking]
+ */
+ unsigned long t_start_time;
+
+ /*
* How many handles used this transaction? [t_handle_lock]
*/
int t_handle_count;
@@ -800,6 +805,8 @@ struct journal_s
pid_t j_last_sync_writer;
+ unsigned long long j_average_commit_time;
+
/*
* An opaque pointer to fs-private information. ext3 puts its
* superblock pointer here
--
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