On 2018/4/12 2:38 PM, tang.junhui@xxxxxxxxxx wrote:
> From: Tang Junhui <tang.junhui@xxxxxxxxxx>
>
> I attached several backend devices in the same cache set, and produced lots
> of dirty data by running small rand I/O writes in a long time, then I
> continue run I/O in the others cached devices, and stopped a cached device,
> after a mean while, I register the stopped device again, I see the running
> I/O in the others cached devices dropped significantly, sometimes even
> jumps to zero.
>
> In currently code, bcache would traverse each keys and btree node to count
> the dirty data under read locker, and the writes threads can not get the
> btree write locker, and when there is a lot of keys and btree node in the
> registering device, it would last several seconds, so the write I/Os in
> others cached device are blocked and declined significantly.
>
> In this patch, when a device registering to a ache set, which exist others
> cached devices with running I/Os, we get the amount of dirty data of the
> device in an incremental way, and do not block other cached devices all the
> time.
>
> Signed-off-by: Tang Junhui <tang.junhui@xxxxxxxxxx>
> ---
> drivers/md/bcache/writeback.c | 26 +++++++++++++++++++++++++-
> 1 file changed, 25 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c
> index 56a3788..2467d3a 100644
> --- a/drivers/md/bcache/writeback.c
> +++ b/drivers/md/bcache/writeback.c
> @@ -488,10 +488,14 @@ static int bch_writeback_thread(void *arg)
> }
>
Hi Junhui,
> /* Init */
> +#define INIT_KEYS_MIN 500000
> +#define INIT_KEYS_SLEEP_TIME 100
>
How about renaming the above macros to something like
INIT_KEYS_WAIT_COUNTER and INIT_KEYS_SLEEP_MS ?
Also I suggested to rename io_inflight in previous patch review comments.
For rested part of this patch looks good to me.
Reviewed-by: Coly Li <colyli@xxxxxxx>
Thanks.
Coly Li
> struct sectors_dirty_init {
> struct btree_op op;
> unsigned inode;
> + size_t count;
> + struct bkey start;
> };
>
> static int sectors_dirty_init_fn(struct btree_op *_op, struct btree *b,
> @@ -506,18 +510,38 @@ static int sectors_dirty_init_fn(struct btree_op *_op, struct btree *b,
> bcache_dev_sectors_dirty_add(b->c, KEY_INODE(k),
> KEY_START(k), KEY_SIZE(k));
>
> + op->count++;
> + if (atomic_read(&b->c->io_inflight) &&
> + !(op->count % INIT_KEYS_MIN)) {
> + bkey_copy_key(&op->start, k);
> + return -EAGAIN;
> + }
> +
> return MAP_CONTINUE;
> }
>
> void bch_sectors_dirty_init(struct bcache_device *d)
> {
> struct sectors_dirty_init op;
> + int ret;
>
> bch_btree_op_init(&op.op, -1);
> op.inode = d->id;
> + op.count = 0;
> + op.start = KEY(op.inode, 0, 0);
>
> - bch_btree_map_keys(&op.op, d->c, &KEY(op.inode, 0, 0),
> + do {
> + ret = bch_btree_map_keys(&op.op, d->c, &op.start,
> sectors_dirty_init_fn, 0);
> + if (ret == -EAGAIN)
> + schedule_timeout_interruptible(
> + msecs_to_jiffies(INIT_KEYS_SLEEP_TIME));
> + else if (ret < 0) {
> + pr_warn("sectors dirty init failed, ret=%d!", ret);
> + break;
> + }
> + } while (ret == -EAGAIN);
> +
> }
>
> void bch_cached_dev_writeback_init(struct cached_dev *dc)
>
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