md raidX make_request functions strip off the BIO_RW_SYNC flag,
this introducing additional latency.
below is a suggested patch for the raid1.c .
other suggested solutions would be to let the bio_clone do its work,
and not reassign thereby stripping off all flags.
at most strip off known unwanted flags (the BARRIER flag).
similar pattern in the other raid versions.
cheers,
Lars
--- /mnt/kernel-src/linux-2.6.19/drivers/md/raid1.c.orig 2006-12-11 10:06:17.661776243 +0100
+++ /mnt/kernel-src/linux-2.6.19/drivers/md/raid1.c 2006-12-12 11:09:55.975762364 +0100
@@ -776,6 +776,7 @@ static int make_request(request_queue_t
struct page **behind_pages = NULL;
const int rw = bio_data_dir(bio);
int do_barriers;
+ int do_sync = bio_sync(bio);
/*
* Register the new request and wait if the reconstruction
@@ -835,7 +836,7 @@ static int make_request(request_queue_t
read_bio->bi_sector = r1_bio->sector + mirror->rdev->data_offset;
read_bio->bi_bdev = mirror->rdev->bdev;
read_bio->bi_end_io = raid1_end_read_request;
- read_bio->bi_rw = READ;
+ read_bio->bi_rw = READ | do_sync;
read_bio->bi_private = r1_bio;
generic_make_request(read_bio);
@@ -906,7 +907,7 @@ static int make_request(request_queue_t
mbio->bi_sector = r1_bio->sector + conf->mirrors[i].rdev->data_offset;
mbio->bi_bdev = conf->mirrors[i].rdev->bdev;
mbio->bi_end_io = raid1_end_write_request;
- mbio->bi_rw = WRITE | do_barriers;
+ mbio->bi_rw = WRITE | do_barriers | do_sync;
mbio->bi_private = r1_bio;
if (behind_pages) {
--
: Lars Ellenberg Tel +43-1-8178292-55 :
: LINBIT Information Technologies GmbH Fax +43-1-8178292-82 :
: Vivenotgasse 48, A-1120 Vienna/Europe http://www.linbit.com :
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