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Message-Id: <20190118115219.63576-3-paolo.valente@linaro.org>
Date: Fri, 18 Jan 2019 12:52:19 +0100
From: Paolo Valente <paolo.valente@...aro.org>
To: Jens Axboe <axboe@...nel.dk>
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
ulf.hansson@...aro.org, linus.walleij@...aro.org,
broonie@...nel.org, bfq-iosched@...glegroups.com,
oleksandr@...alenko.name, hurikhan77+bko@...il.com,
Paolo Valente <paolo.valente@...aro.org>
Subject: [PATCH BUGFIX RFC 2/2] Revert "bfq: calculate shallow depths at init time"
This reverts commit f0635b8a416e3b99dc6fd9ac3ce534764869d0c8.
---
block/bfq-iosched.c | 117 +++++++++++++++++++++-----------------------
1 file changed, 57 insertions(+), 60 deletions(-)
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 8cc3032b66de..92214d58510c 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -520,6 +520,54 @@ static struct request *bfq_choose_req(struct bfq_data *bfqd,
}
}
+/*
+ * See the comments on bfq_limit_depth for the purpose of
+ * the depths set in the function. Return minimum shallow depth we'll use.
+ */
+static unsigned int bfq_update_depths(struct bfq_data *bfqd,
+ struct sbitmap_queue *bt)
+{
+ unsigned int i, j, min_shallow = UINT_MAX;
+ bfqd->sb_shift = bt->sb.shift;
+
+ /*
+ * In-word depths if no bfq_queue is being weight-raised:
+ * leaving 25% of tags only for sync reads.
+ *
+ * In next formulas, right-shift the value
+ * (1U<<bfqd->sb_shift), instead of computing directly
+ * (1U<<(bfqd->sb_shift - something)), to be robust against
+ * any possible value of bfqd->sb_shift, without having to
+ * limit 'something'.
+ */
+ /* no more than 50% of tags for async I/O */
+ bfqd->word_depths[0][0] = max((1U<<bfqd->sb_shift)>>1, 1U);
+ /*
+ * no more than 75% of tags for sync writes (25% extra tags
+ * w.r.t. async I/O, to prevent async I/O from starving sync
+ * writes)
+ */
+ bfqd->word_depths[0][1] = max(((1U<<bfqd->sb_shift) * 3)>>2, 1U);
+
+ /*
+ * In-word depths in case some bfq_queue is being weight-
+ * raised: leaving ~63% of tags for sync reads. This is the
+ * highest percentage for which, in our tests, application
+ * start-up times didn't suffer from any regression due to tag
+ * shortage.
+ */
+ /* no more than ~18% of tags for async I/O */
+ bfqd->word_depths[1][0] = max(((1U<<bfqd->sb_shift) * 3)>>4, 1U);
+ /* no more than ~37% of tags for sync writes (~20% extra tags) */
+ bfqd->word_depths[1][1] = max(((1U<<bfqd->sb_shift) * 6)>>4, 1U);
+
+ for (i = 0; i < 2; i++)
+ for (j = 0; j < 2; j++)
+ min_shallow = min(min_shallow, bfqd->word_depths[i][j]);
+
+ return min_shallow;
+}
+
/*
* Async I/O can easily starve sync I/O (both sync reads and sync
* writes), by consuming all tags. Similarly, storms of sync writes,
@@ -529,11 +577,20 @@ static struct request *bfq_choose_req(struct bfq_data *bfqd,
*/
static void bfq_limit_depth(unsigned int op, struct blk_mq_alloc_data *data)
{
+ struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
struct bfq_data *bfqd = data->q->elevator->elevator_data;
+ struct sbitmap_queue *bt;
if (op_is_sync(op) && !op_is_write(op))
return;
+ bt = &tags->bitmap_tags;
+
+ if (unlikely(bfqd->sb_shift != bt->sb.shift)) {
+ unsigned int min_shallow = bfq_update_depths(bfqd, bt);
+ sbitmap_queue_min_shallow_depth(&tags->bitmap_tags, min_shallow);
+ }
+
data->shallow_depth =
bfqd->word_depths[!!bfqd->wr_busy_queues][op_is_sync(op)];
@@ -5295,65 +5352,6 @@ void bfq_put_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg)
__bfq_put_async_bfqq(bfqd, &bfqg->async_idle_bfqq);
}
-/*
- * See the comments on bfq_limit_depth for the purpose of
- * the depths set in the function. Return minimum shallow depth we'll use.
- */
-static unsigned int bfq_update_depths(struct bfq_data *bfqd,
- struct sbitmap_queue *bt)
-{
- unsigned int i, j, min_shallow = UINT_MAX;
- bfqd->sb_shift = bt->sb.shift;
-
- /*
- * In-word depths if no bfq_queue is being weight-raised:
- * leaving 25% of tags only for sync reads.
- *
- * In next formulas, right-shift the value
- * (1U<<bfqd->sb_shift), instead of computing directly
- * (1U<<(bfqd->sb_shift - something)), to be robust against
- * any possible value of bfqd->sb_shift, without having to
- * limit 'something'.
- */
- /* no more than 50% of tags for async I/O */
- bfqd->word_depths[0][0] = max((1U<<bfqd->sb_shift)>>1, 1U);
- /*
- * no more than 75% of tags for sync writes (25% extra tags
- * w.r.t. async I/O, to prevent async I/O from starving sync
- * writes)
- */
- bfqd->word_depths[0][1] = max(((1U<<bfqd->sb_shift) * 3)>>2, 1U);
-
- /*
- * In-word depths in case some bfq_queue is being weight-
- * raised: leaving ~63% of tags for sync reads. This is the
- * highest percentage for which, in our tests, application
- * start-up times didn't suffer from any regression due to tag
- * shortage.
- */
- /* no more than ~18% of tags for async I/O */
- bfqd->word_depths[1][0] = max(((1U<<bfqd->sb_shift) * 3)>>4, 1U);
- /* no more than ~37% of tags for sync writes (~20% extra tags) */
- bfqd->word_depths[1][1] = max(((1U<<bfqd->sb_shift) * 6)>>4, 1U);
-
- for (i = 0; i < 2; i++)
- for (j = 0; j < 2; j++)
- min_shallow = min(min_shallow, bfqd->word_depths[i][j]);
-
- return min_shallow;
-}
-
-static int bfq_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int index)
-{
- struct bfq_data *bfqd = hctx->queue->elevator->elevator_data;
- struct blk_mq_tags *tags = hctx->sched_tags;
- unsigned int min_shallow;
-
- min_shallow = bfq_update_depths(bfqd, &tags->bitmap_tags);
- sbitmap_queue_min_shallow_depth(&tags->bitmap_tags, min_shallow);
- return 0;
-}
-
static void bfq_exit_queue(struct elevator_queue *e)
{
struct bfq_data *bfqd = e->elevator_data;
@@ -5773,7 +5771,6 @@ static struct elevator_type iosched_bfq_mq = {
.requests_merged = bfq_requests_merged,
.request_merged = bfq_request_merged,
.has_work = bfq_has_work,
- .init_hctx = bfq_init_hctx,
.init_sched = bfq_init_queue,
.exit_sched = bfq_exit_queue,
},
--
2.20.1
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