aboutsummaryrefslogtreecommitdiffstats
path: root/fs/btrfs/volumes.c
diff options
context:
space:
mode:
authorChris Mason <chris.mason@oracle.com>2009-04-03 10:27:10 -0400
committerChris Mason <chris.mason@oracle.com>2009-04-03 10:27:10 -0400
commitb765ead57da62cccf7fa21e00e6eed65e9df62b0 (patch)
tree66541fd018482a8d0db0021c3a3f3e8611ddb6fe /fs/btrfs/volumes.c
parentd57e62b89796f751c9422801cbcd407a9f8dcdc4 (diff)
Btrfs: keep processing bios for a given bdev if our proc is batching
Btrfs uses async helper threads to submit write bios so the checksumming helper threads don't block on the disk. The submit bio threads may process bios for more than one block device, so when they find one device congested they try to move on to other devices instead of blocking in get_request_wait for one device. This does a pretty good job of keeping multiple devices busy, but the congested flag has a number of problems. A congested device may still give you a request, and other procs that aren't backing off the congested device may starve you out. This commit uses the io_context stored in current to decide if our process has been made a batching process by the block layer. If so, it keeps sending IO down for at least one batch. This helps make sure we do a good amount of work each time we visit a bdev, and avoids large IO stalls in multi-device workloads. It's also very ugly. A better solution is in the works with Jens Axboe. Signed-off-by: Chris Mason <chris.mason@oracle.com>
Diffstat (limited to 'fs/btrfs/volumes.c')
-rw-r--r--fs/btrfs/volumes.c27
1 files changed, 27 insertions, 0 deletions
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index dd06e18e5aac..cc01abff03d9 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -20,6 +20,7 @@
20#include <linux/buffer_head.h> 20#include <linux/buffer_head.h>
21#include <linux/blkdev.h> 21#include <linux/blkdev.h>
22#include <linux/random.h> 22#include <linux/random.h>
23#include <linux/iocontext.h>
23#include <asm/div64.h> 24#include <asm/div64.h>
24#include "compat.h" 25#include "compat.h"
25#include "ctree.h" 26#include "ctree.h"
@@ -145,6 +146,7 @@ static noinline int run_scheduled_bios(struct btrfs_device *device)
145 int again = 0; 146 int again = 0;
146 unsigned long num_run = 0; 147 unsigned long num_run = 0;
147 unsigned long limit; 148 unsigned long limit;
149 unsigned long last_waited = 0;
148 150
149 bdi = device->bdev->bd_inode->i_mapping->backing_dev_info; 151 bdi = device->bdev->bd_inode->i_mapping->backing_dev_info;
150 fs_info = device->dev_root->fs_info; 152 fs_info = device->dev_root->fs_info;
@@ -207,7 +209,32 @@ loop_lock:
207 if (pending && bdi_write_congested(bdi) && num_run > 16 && 209 if (pending && bdi_write_congested(bdi) && num_run > 16 &&
208 fs_info->fs_devices->open_devices > 1) { 210 fs_info->fs_devices->open_devices > 1) {
209 struct bio *old_head; 211 struct bio *old_head;
212 struct io_context *ioc;
210 213
214 ioc = current->io_context;
215
216 /*
217 * the main goal here is that we don't want to
218 * block if we're going to be able to submit
219 * more requests without blocking.
220 *
221 * This code does two great things, it pokes into
222 * the elevator code from a filesystem _and_
223 * it makes assumptions about how batching works.
224 */
225 if (ioc && ioc->nr_batch_requests > 0 &&
226 time_before(jiffies, ioc->last_waited + HZ/50UL) &&
227 (last_waited == 0 ||
228 ioc->last_waited == last_waited)) {
229 /*
230 * we want to go through our batch of
231 * requests and stop. So, we copy out
232 * the ioc->last_waited time and test
233 * against it before looping
234 */
235 last_waited = ioc->last_waited;
236 continue;
237 }
211 spin_lock(&device->io_lock); 238 spin_lock(&device->io_lock);
212 239
213 old_head = device->pending_bios; 240 old_head = device->pending_bios;