bcache: Performance fix for when journal entry is full

We were unnecessarily waiting on a journal write to complete when we just needed
to start a journal write and start setting up the next one.

Signed-off-by: Kent Overstreet <kmo@daterainc.com>

diff --git a/drivers/md/bcache/journal.c b/drivers/md/bcache/journal.c
index 29cccc510eb6e1564a858420a0c6242e8ee4229f..ad687285c2df8da0782f2f0eb429f92d8cf013ef 100644 (file)
--- a/drivers/md/bcache/journal.c
+++ b/drivers/md/bcache/journal.c
@@ -673,6 +673,7 @@ static struct journal_write *journal_wait_for_write(struct cache_set *c,
 {
        size_t sectors;
        struct closure cl;
+       bool wait = false;
 
        closure_init_stack(&cl);
 
@@ -689,9 +690,12 @@ static struct journal_write *journal_wait_for_write(struct cache_set *c,
                                     PAGE_SECTORS << JSET_BITS))
                        return w;
 
-               /* XXX: tracepoint */
+               if (wait)
+                       closure_wait(&c->journal.wait, &cl);
+
                if (!journal_full(&c->journal)) {
-                       trace_bcache_journal_entry_full(c);
+                       if (wait)
+                               trace_bcache_journal_entry_full(c);
 
                        /*
                         * XXX: If we were inserting so many keys that they
@@ -701,12 +705,11 @@ static struct journal_write *journal_wait_for_write(struct cache_set *c,
                         */
                        BUG_ON(!w->data->keys);
 
-                       closure_wait(&w->wait, &cl);
                        journal_try_write(c); /* unlocks */
                } else {
-                       trace_bcache_journal_full(c);
+                       if (wait)
+                               trace_bcache_journal_full(c);
 
-                       closure_wait(&c->journal.wait, &cl);
                        journal_reclaim(c);
                        spin_unlock(&c->journal.lock);
 
@@ -715,6 +718,7 @@ static struct journal_write *journal_wait_for_write(struct cache_set *c,
 
                closure_sync(&cl);
                spin_lock(&c->journal.lock);
+               wait = true;
        }
 }