To improve write perfomance by decreasing the preread stripe,only move
IO_THRESHOLD stripes from delay_list to hold_list once.
Using the follow command:
dd if=/dev/zero of=/dev/md0 bs=2M count=52100.
At default condition: speed is 95MB/s.
At the condition of preread_bypass_threshold was equal zero:speed is 105MB/s.
Using this patch:speed is 123MB/s.
If preread_bypass_threshold was zero,the performance will be better,but
not better than this patch.
I think maybe two reason:
1:If bio is REQ_SYNC
2:In function __get_priority_stripe():
>> } else if (!list_empty(&conf->hold_list) &&
>> ((conf->bypass_threshold &&
>> conf->bypass_count > conf->bypass_threshold) ||
>> atomic_read(&conf->pending_full_writes) == 0)) {
Preread_bypass_threshold is one condition of getting stripe from
hold_list.So only control the number of hold_list can get better
performance.
Signed-off-by: Jianpeng Ma <majianpeng@xxxxxxxxx>
---
drivers/md/raid5.c | 3 +++
1 files changed, 3 insertions(+), 0 deletions(-)
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 04348d7..a6749bb 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -3662,6 +3662,7 @@ finish:
static void raid5_activate_delayed(struct r5conf *conf)
{
+ int count = 0;
if (atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD) {
while (!list_empty(&conf->delayed_list)) {
struct list_head *l = conf->delayed_list.next;
@@ -3672,6 +3673,8 @@ static void raid5_activate_delayed(struct r5conf *conf)
if (!test_and_set_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
atomic_inc(&conf->preread_active_stripes);
list_add_tail(&sh->lru, &conf->hold_list);
+ if (++count >= IO_THRESHOLD)
+ break;
}
}
}
--
1.7.5.4
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