@@ -487,6 +487,20 @@ static struct request *dd_dispatch_request(struct blk_mq_hw_ctx *hctx)
return rq;
}
+/*
+ * 'depth' is a number in the range 1..INT_MAX representing a number of
+ * requests. Scale it with a factor (1 << bt->sb.shift) /
+q->nr_requests since
+ * 1..(1 << bt->sb.shift) is the range expected by sbitmap_get_shallow().
+ * Values larger than q->nr_requests have the same effect as q->nr_requests.
+ */
+static int dd_to_word_depth(struct blk_mq_hw_ctx *hctx, unsigned int
+qdepth) {
+ struct sbitmap_queue *bt = &hctx->sched_tags->bitmap_tags;
+ const unsigned int nrr = hctx->queue->nr_requests;
+
+ return ((qdepth << bt->sb.shift) + nrr - 1) / nrr; }
+
/*
* Called by __blk_mq_alloc_request(). The shallow_depth value set by this
* function is used by __blk_mq_get_tag().
@@ -503,7 +517,7 @@ static void dd_limit_depth(blk_opf_t opf, struct blk_mq_alloc_data *data)
* Throttle asynchronous requests and writes such that these requests
* do not block the allocation of synchronous requests.
*/
- data->shallow_depth = dd->async_depth;
+ data->shallow_depth = dd_to_word_depth(data->hctx,
+ dd->async_depth);
}
/* Called by blk_mq_update_nr_requests(). */ @@ -513,9 +527,9 @@ static void dd_depth_updated(struct blk_mq_hw_ctx *hctx)
-----邮件原件----- 发件人: Bart Van Assche <bvanassche@acm.org> 发送时间: 2024年5月10日 1:02 收件人: Jens Axboe <axboe@kernel.dk> 抄送: linux-block@vger.kernel.org; Christoph Hellwig <hch@lst.de>; Bart Van Assche <bvanassche@acm.org>; Damien Le Moal <dlemoal@kernel.org>; 牛志国 (Zhiguo Niu) <Zhiguo.Niu@unisoc.com> 主题: [PATCH v2 2/2] block/mq-deadline: Fix the tag reservation code 注意: 这封邮件来自于外部。除非你确定邮件内容安全，否则不要点击任何链接和附件。 CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe. The current tag reservation code is based on a misunderstanding of the meaning of data->shallow_depth. Fix the tag reservation code as follows: * By default, do not reserve any tags for synchronous requests because for certain use cases reserving tags reduces performance. See also Harshit Mogalapalli, [bug-report] Performance regression with fio sequential-write on a multipath setup, 2024-03-07 (https://lore.kernel.org/linux-block/5ce2ae5d-61e2-4ede-ad55-551112602401@oracle.com/) * Reduce min_shallow_depth to one because min_shallow_depth must be less than or equal any shallow_depth value. * Scale dd->async_depth from the range [1, nr_requests] to [1, bits_per_sbitmap_word]. Cc: Christoph Hellwig <hch@lst.de> Cc: Damien Le Moal <dlemoal@kernel.org> Cc: Zhiguo Niu <zhiguo.niu@unisoc.com> Fixes: 07757588e507 ("block/mq-deadline: Reserve 25% of scheduler tags for synchronous requests") Signed-off-by: Bart Van Assche <bvanassche@acm.org> --- block/mq-deadline.c | 20 +++++++++++++++++--- 1 file changed, 17 insertions(+), 3 deletions(-) struct deadline_data *dd = q->elevator->elevator_data; struct blk_mq_tags *tags = hctx->sched_tags; - dd->async_depth = max(1UL, 3 * q->nr_requests / 4); + dd->async_depth = q->nr_requests; - sbitmap_queue_min_shallow_depth(&tags->bitmap_tags, dd->async_depth); + sbitmap_queue_min_shallow_depth(&tags->bitmap_tags, 1); } Hi Bart, I tested basic function about these serial patches and results is pass, and no warning report after setting async_depth value by sysfs, so Tested-by: Zhiguo Niu <zhiguo.niu@unisoc.com> Thanks! /* Called by blk_mq_init_hctx() and blk_mq_init_sched(). */