2012/8/7 Jianpeng Ma <majianpeng@xxxxxxxxx>:
> On 2012-08-07 11:22 Shaohua Li <shli@xxxxxxxxxx> Wrote:
>>My directIO randomwrite 4k workload shows a 10~20% regression caused by commit
>>895e3c5c58a80bb. directIO usually is random IO and if request size isn't big
>>(which is the common case), delay handling of the stripe hasn't any advantages.
>>For big size request, delay can still reduce IO.
>>
>>Signed-off-by: Shaohua Li <shli@xxxxxxxxxxxx>
>>---
>> drivers/md/raid5.c | 9 ++++++++-
>> 1 file changed, 8 insertions(+), 1 deletion(-)
>>
>>Index: linux/drivers/md/raid5.c
>>===================================================================
>>--- linux.orig/drivers/md/raid5.c 2012-08-07 11:04:48.442834682 +0800
>>+++ linux/drivers/md/raid5.c 2012-08-07 11:09:08.743562203 +0800
>>@@ -4076,6 +4076,7 @@ static void make_request(struct mddev *m
>> struct stripe_head *sh;
>> const int rw = bio_data_dir(bi);
>> int remaining;
>>+ bool large_request;
>>
>> if (unlikely(bi->bi_rw & REQ_FLUSH)) {
>> md_flush_request(mddev, bi);
>>@@ -4089,6 +4090,11 @@ static void make_request(struct mddev *m
>> chunk_aligned_read(mddev,bi))
>> return;
>>
>>+ if (mddev->new_chunk_sectors < mddev->chunk_sectors)
>>+ large_request = (bi->bi_size >> 9) > mddev->new_chunk_sectors;
>>+ else
>>+ large_request = (bi->bi_size >> 9) > mddev->chunk_sectors;
>>+
>> logical_sector = bi->bi_sector & ~((sector_t)STRIPE_SECTORS-1);
>> last_sector = bi->bi_sector + (bi->bi_size>>9);
>> bi->bi_next = NULL;
>>@@ -4192,7 +4198,8 @@ static void make_request(struct mddev *m
>> finish_wait(&conf->wait_for_overlap, &w);
>> set_bit(STRIPE_HANDLE, &sh->state);
>> clear_bit(STRIPE_DELAYED, &sh->state);
>>- if ((bi->bi_rw & REQ_NOIDLE) &&
>>+ if ((bi->bi_rw & REQ_SYNC) &&
>>+ ((bi->bi_rw & REQ_NOIDLE) || !large_request) &&
>> !test_and_set_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
>> atomic_inc(&conf->preread_active_stripes);
>> release_stripe_plug(mddev, sh);
>>--
> May be used size to judge is not a good method.
> I firstly sended this patch, only want to control direct-write-block,not for reqular file.
> Because i think if someone used direct-write-block for raid5,he should know the feature of raid5 and he can control
> for write to full-write.
> But at that time, i did know how to differentiate between regular file and block-device.
> I thik we should do something to do this.
I don't think it's possible user can control his write to be a
full-write even for
raw disk IO. Why regular file and block device io matters here?
Thanks,
Shaohua
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