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Revert "xen/blkback: Move the plugging/unplugging to a higher level."

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This reverts commit 97961ef46b b/c
we lose about 15% performance if we do the unplugging and the
end of the reading the ring buffer.
This commit is contained in:
Konrad Rzeszutek Wilk 2011-04-27 12:40:11 -04:00
parent 013c3ca184
commit a19be5f0f0
1 changed files with 7 additions and 6 deletions
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13
drivers/block/xen-blkback/blkback.c
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@ -276,8 +276,6 @@ int xen_blkif_schedule(void *arg)
printk(KERN_DEBUG "%s: started\n", current->comm); printk(KERN_DEBUG "%s: started\n", current->comm);
while (!kthread_should_stop()) { while (!kthread_should_stop()) {
struct blk_plug plug;
if (try_to_freeze()) if (try_to_freeze())
continue; continue;
if (unlikely(vbd->size != vbd_sz(vbd))) if (unlikely(vbd->size != vbd_sz(vbd)))
@ -294,13 +292,9 @@ int xen_blkif_schedule(void *arg)
blkif->waiting_reqs = 0; blkif->waiting_reqs = 0;
smp_mb(); /* clear flag *before* checking for work */ smp_mb(); /* clear flag *before* checking for work */
blk_start_plug(&plug);
if (do_block_io_op(blkif)) if (do_block_io_op(blkif))
blkif->waiting_reqs = 1; blkif->waiting_reqs = 1;
blk_finish_plug(&plug);
if (log_stats && time_after(jiffies, blkif->st_print)) if (log_stats && time_after(jiffies, blkif->st_print))
print_stats(blkif); print_stats(blkif);
} }
@ -553,6 +547,7 @@ static void dispatch_rw_block_io(struct blkif_st *blkif,
struct bio *biolist[BLKIF_MAX_SEGMENTS_PER_REQUEST]; struct bio *biolist[BLKIF_MAX_SEGMENTS_PER_REQUEST];
int i, nbio = 0; int i, nbio = 0;
int operation; int operation;
struct blk_plug plug;
switch (req->operation) { switch (req->operation) {
case BLKIF_OP_READ: case BLKIF_OP_READ:
@ -665,9 +660,15 @@ static void dispatch_rw_block_io(struct blkif_st *blkif,
*/ */
atomic_set(&pending_req->pendcnt, nbio); 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++) for (i = 0; i < nbio; i++)
submit_bio(operation, biolist[i]); submit_bio(operation, biolist[i]);
blk_finish_plug(&plug);
/* Let the I/Os go.. */
if (operation == READ) if (operation == READ)
blkif->st_rd_sect += preq.nr_sects; blkif->st_rd_sect += preq.nr_sects;
else if (operation == WRITE || operation == WRITE_BARRIER) else if (operation == WRITE || operation == WRITE_BARRIER)