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Commit a19be5f0 authored by Konrad Rzeszutek Wilk's avatar Konrad Rzeszutek Wilk
Browse files

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

This reverts commit 97961ef4 b/c
we lose about 15% performance if we do the unplugging and the
end of the reading the ring buffer.
parent 013c3ca1

drivers/block/xen-blkback/blkback.c

+7 −6
Original line number Diff line number Diff line
@@ -276,8 +276,6 @@ int xen_blkif_schedule(void *arg) 
		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 @@ int xen_blkif_schedule(void *arg) 
		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 @@ static void dispatch_rw_block_io(struct blkif_st *blkif, 
	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 @@ static void dispatch_rw_block_io(struct blkif_st *blkif, 
	 */

	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)