raid5: make_request does less prepare wait
In NUMA machine, prepare_to_wait/finish_wait in make_request exposes a
lot of contention for sequential workload (or big request size
workload). For such workload, each bio includes several stripes. So we
can just do prepare_to_wait/finish_wait once for the whold bio instead
of every stripe. This reduces the lock contention completely for such
workload. Random workload might have the similar lock contention too,
but I didn't see it yet, maybe because my stroage is still not fast
enough.
Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: NeilBrown <neilb@suse.de>
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 16f5c21..a904a2c 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -4552,6 +4552,8 @@
struct stripe_head *sh;
const int rw = bio_data_dir(bi);
int remaining;
+ DEFINE_WAIT(w);
+ bool do_prepare;
if (unlikely(bi->bi_rw & REQ_FLUSH)) {
md_flush_request(mddev, bi);
@@ -4575,15 +4577,18 @@
bi->bi_next = NULL;
bi->bi_phys_segments = 1; /* over-loaded to count active stripes */
+ prepare_to_wait(&conf->wait_for_overlap, &w, TASK_UNINTERRUPTIBLE);
for (;logical_sector < last_sector; logical_sector += STRIPE_SECTORS) {
- DEFINE_WAIT(w);
int previous;
int seq;
+ do_prepare = false;
retry:
seq = read_seqcount_begin(&conf->gen_lock);
previous = 0;
- prepare_to_wait(&conf->wait_for_overlap, &w, TASK_UNINTERRUPTIBLE);
+ if (do_prepare)
+ prepare_to_wait(&conf->wait_for_overlap, &w,
+ TASK_UNINTERRUPTIBLE);
if (unlikely(conf->reshape_progress != MaxSector)) {
/* spinlock is needed as reshape_progress may be
* 64bit on a 32bit platform, and so it might be
@@ -4604,6 +4609,7 @@
: logical_sector >= conf->reshape_safe) {
spin_unlock_irq(&conf->device_lock);
schedule();
+ do_prepare = true;
goto retry;
}
}
@@ -4640,6 +4646,7 @@
if (must_retry) {
release_stripe(sh);
schedule();
+ do_prepare = true;
goto retry;
}
}
@@ -4663,8 +4670,10 @@
prepare_to_wait(&conf->wait_for_overlap,
&w, TASK_INTERRUPTIBLE);
if (logical_sector >= mddev->suspend_lo &&
- logical_sector < mddev->suspend_hi)
+ logical_sector < mddev->suspend_hi) {
schedule();
+ do_prepare = true;
+ }
goto retry;
}
@@ -4677,9 +4686,9 @@
md_wakeup_thread(mddev->thread);
release_stripe(sh);
schedule();
+ do_prepare = true;
goto retry;
}
- finish_wait(&conf->wait_for_overlap, &w);
set_bit(STRIPE_HANDLE, &sh->state);
clear_bit(STRIPE_DELAYED, &sh->state);
if ((bi->bi_rw & REQ_SYNC) &&
@@ -4689,10 +4698,10 @@
} else {
/* cannot get stripe for read-ahead, just give-up */
clear_bit(BIO_UPTODATE, &bi->bi_flags);
- finish_wait(&conf->wait_for_overlap, &w);
break;
}
}
+ finish_wait(&conf->wait_for_overlap, &w);
remaining = raid5_dec_bi_active_stripes(bi);
if (remaining == 0) {