Revert "xen/blkback: Move the plugging/unplugging to a higher level."
This reverts commit 97961ef46b9b5a6a7c918a38b898a7b3e49869f4 b/c
we lose about 15% performance if we do the unplugging and the
end of the reading the ring buffer.
diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index 8583b13..eb068d0 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -276,8 +276,6 @@
printk(KERN_DEBUG "%s: started\n", current->comm);
while (!kthread_should_stop()) {
- struct blk_plug plug;
-
if (try_to_freeze())
continue;
if (unlikely(vbd->size != vbd_sz(vbd)))
@@ -294,13 +292,9 @@
blkif->waiting_reqs = 0;
smp_mb(); /* clear flag *before* checking for work */
- blk_start_plug(&plug);
-
if (do_block_io_op(blkif))
blkif->waiting_reqs = 1;
- blk_finish_plug(&plug);
-
if (log_stats && time_after(jiffies, blkif->st_print))
print_stats(blkif);
}
@@ -553,6 +547,7 @@
struct bio *biolist[BLKIF_MAX_SEGMENTS_PER_REQUEST];
int i, nbio = 0;
int operation;
+ struct blk_plug plug;
switch (req->operation) {
case BLKIF_OP_READ:
@@ -665,9 +660,15 @@
*/
atomic_set(&pending_req->pendcnt, nbio);
+ /* Get a reference count for the disk queue and start sending I/O */
+ blk_start_plug(&plug);
+
for (i = 0; i < nbio; i++)
submit_bio(operation, biolist[i]);
+ blk_finish_plug(&plug);
+ /* Let the I/Os go.. */
+
if (operation == READ)
blkif->st_rd_sect += preq.nr_sects;
else if (operation == WRITE || operation == WRITE_BARRIER)