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Subjectminor JBD tunings
From
Date

hi!

I'm trying to improve JBD performance. please, take a look at numbers.

creation of 500K files in single dir (with htree, of course):
before: 4m16.094s, 4m12.035s, 4m11.911s
after: 1m41.364s, 1m43.461s, 1m45.189s

removal of 500K files in single dir:
before: 43m50.161s
after: 38m45.510s
patches are attached

with best regards, Alex Tomas



start_this_handle() takes in account t_outstanding_credits calculating
log free space, but journal_next_log_block() accounts blocks being logged
also. hence, blocks are accounting twice. we don't want this.




diff -puN fs/jbd/commit.c~jbd-dont-account-blocks-twice fs/jbd/commit.c
--- linux-2.5.73/fs/jbd/commit.c~jbd-dont-account-blocks-twice Sun Jun 29 13:20:23 2003
+++ linux-2.5.73-alexey/fs/jbd/commit.c Sun Jun 29 13:22:33 2003
@@ -401,6 +401,11 @@ sync_datalist_empty:
continue;
}

+ /* start_this_handle() accounts t_outstanding_credits
+ * to know free space in log, but this counter is changed
+ * by journal_next_log_block() also. */
+ commit_transaction->t_outstanding_credits--;
+
/* Bump b_count to prevent truncate from stumbling over
the shadowed buffer! @@@ This can go if we ever get
rid of the BJ_IO/BJ_Shadow pairing of buffers. */
_

- __log_wait_for_space() recalculates needed blocks because journal free
space changes during commit
- log_do_checkpoint() starts scaning from the oldest transaction
- log_do_checkpoint() stop scaning if some transaction gets dropped




diff -puN fs/jbd/checkpoint.c~jbd-commit-tricks fs/jbd/checkpoint.c
--- linux-2.5.73/fs/jbd/checkpoint.c~jbd-commit-tricks Fri Jul 4 18:02:02 2003
+++ linux-2.5.73-alexey/fs/jbd/checkpoint.c Fri Jul 4 18:12:40 2003
@@ -80,6 +80,10 @@ void __log_wait_for_space(journal_t *jou
{
assert_spin_locked(&journal->j_state_lock);

+ nblocks = journal->j_max_transaction_buffers;
+ if (journal->j_committing_transaction)
+ nblocks += journal->j_committing_transaction->
+ t_outstanding_credits;
while (__log_space_left(journal) < nblocks) {
if (journal->j_flags & JFS_ABORT)
return;
@@ -91,6 +95,10 @@ void __log_wait_for_space(journal_t *jou
* were waiting for the checkpoint lock
*/
spin_lock(&journal->j_state_lock);
+ nblocks = journal->j_max_transaction_buffers;
+ if (journal->j_committing_transaction)
+ nblocks += journal->j_committing_transaction->
+ t_outstanding_credits;
if (__log_space_left(journal) < nblocks) {
spin_unlock(&journal->j_state_lock);
log_do_checkpoint(journal, nblocks);
@@ -225,11 +233,13 @@ __flush_batch(journal_t *journal, struct
*/
static int __flush_buffer(journal_t *journal, struct journal_head *jh,
struct buffer_head **bhs, int *batch_count,
- int *drop_count)
+ int *drop_count, int *freed)
{
struct buffer_head *bh = jh2bh(jh);
int ret = 0;

+ *freed = 1;
+
if (buffer_dirty(bh) && !buffer_locked(bh) && jh->b_jlist == BJ_None) {
J_ASSERT_JH(jh, jh->b_transaction == NULL);

@@ -262,6 +272,8 @@ static int __flush_buffer(journal_t *jou
if (__try_to_free_cp_buf(jh)) {
(*drop_count)++;
ret = last_buffer;
+ if (last_buffer)
+ *freed = 1;
}
}
return ret;
@@ -286,6 +298,7 @@ int log_do_checkpoint(journal_t *journal
int result;
int batch_count = 0;
struct buffer_head *bhs[NR_BATCH];
+ int stid;

jbd_debug(1, "Start checkpoint\n");

@@ -308,14 +321,23 @@ int log_do_checkpoint(journal_t *journal
* degenerates into a busy loop at unmount time.
*/
spin_lock(&journal->j_list_lock);
+ if (journal->j_checkpoint_transactions)
+ stid = journal->j_checkpoint_transactions->t_tid - 1;
while (journal->j_checkpoint_transactions) {
transaction_t *transaction;
struct journal_head *jh, *last_jh, *next_jh;
int drop_count = 0;
int cleanup_ret, retry = 0;
tid_t this_tid;
+ int freed = 0;

- transaction = journal->j_checkpoint_transactions->t_cpnext;
+ transaction = journal->j_checkpoint_transactions;
+ while (transaction->t_tid <= stid) {
+ transaction = transaction->t_cpnext;
+ if (transaction == journal->j_checkpoint_transactions)
+ goto finish;
+ }
+ stid = transaction->t_tid;
this_tid = transaction->t_tid;
jh = transaction->t_checkpoint_list;
last_jh = jh->b_cpprev;
@@ -333,15 +355,22 @@ int log_do_checkpoint(journal_t *journal
break;
}
retry = __flush_buffer(journal, jh, bhs, &batch_count,
- &drop_count);
+ &drop_count, &freed);
} while (jh != last_jh && !retry);
- if (batch_count) {
+
+ if (batch_count)
__flush_batch(journal, bhs, &batch_count);
+ /*
+ * transaction was freed, so we're gonna return to check is
+ * log has enough space for next transaction
+ */
+ if (freed)
+ break;
+
+ if (retry) {
+ stid--;
continue;
}
- if (retry)
- continue;
-
/*
* If someone emptied the checkpoint list while we slept, we're
* done.
@@ -349,12 +378,6 @@ int log_do_checkpoint(journal_t *journal
if (!journal->j_checkpoint_transactions)
break;
/*
- * If someone cleaned up this transaction while we slept, we're
- * done
- */
- if (journal->j_checkpoint_transactions->t_cpnext != transaction)
- continue;
- /*
* Maybe it's a new transaction, but it fell at the same
* address
*/
@@ -368,6 +391,7 @@ int log_do_checkpoint(journal_t *journal
cleanup_ret = __cleanup_transaction(journal, transaction);
J_ASSERT(drop_count != 0 || cleanup_ret != 0);
}
+finish:
spin_unlock(&journal->j_list_lock);
result = cleanup_journal_tail(journal);
if (result < 0)
diff -puN fs/jbd/commit.c~jbd-commit-tricks fs/jbd/commit.c
_
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