From: Jens Axboe <axboe@kernel.dk>
Date: Mon, 7 May 2018 10:03:23 -0600
Subject: [PATCH] blk-wbt: throttle discards like background writes
Git-commit: 782f569774d7000e54ae9d680b0e4cd29b1c7ca3
Patch-mainline: v4.18-rc1
References: bsc#1104967,FATE#325924
Throttle discards like we would any background write. Discards should
be background activity, so if they are impacting foreground IO, then
we will throttle them down.
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Hannes Reinecke <hare@suse.com>
---
block/blk-stat.h | 6 +++---
block/blk-wbt.c | 43 ++++++++++++++++++++++++++-----------------
block/blk-wbt.h | 4 +++-
3 files changed, 32 insertions(+), 21 deletions(-)
diff --git a/block/blk-stat.h b/block/blk-stat.h
index 2dd36347252a..c22049a8125e 100644
--- a/block/blk-stat.h
+++ b/block/blk-stat.h
@@ -10,11 +10,11 @@
/*
* from upper:
- * 3 bits: reserved for other usage
+ * 4 bits: reserved for other usage
* 12 bits: size
- * 49 bits: time
+ * 48 bits: time
*/
-#define BLK_STAT_RES_BITS 3
+#define BLK_STAT_RES_BITS 4
#define BLK_STAT_SIZE_BITS 12
#define BLK_STAT_RES_SHIFT (64 - BLK_STAT_RES_BITS)
#define BLK_STAT_SIZE_SHIFT (BLK_STAT_RES_SHIFT - BLK_STAT_SIZE_BITS)
diff --git a/block/blk-wbt.c b/block/blk-wbt.c
index 25d202345965..a7a724580033 100644
--- a/block/blk-wbt.c
+++ b/block/blk-wbt.c
@@ -106,6 +106,8 @@ static inline struct rq_wait *get_rq_wait(struct rq_wb *rwb,
{
if (wb_acct & WBT_KSWAPD)
return &rwb->rq_wait[WBT_RWQ_KSWAPD];
+ else if (wb_acct & WBT_DISCARD)
+ return &rwb->rq_wait[WBT_RWQ_DISCARD];
return &rwb->rq_wait[WBT_RWQ_BG];
}
@@ -143,10 +145,13 @@ void __wbt_done(struct rq_wb *rwb, enum wbt_flags wb_acct)
}
/*
- * If the device does write back caching, drop further down
- * before we wake people up.
+ * For discards, our limit is always the background. For writes, if
+ * the device does write back caching, drop further down before we
+ * wake people up.
*/
- if (rwb->wc && !wb_recent_wait(rwb))
+ if (wb_acct & WBT_DISCARD)
+ limit = rwb->wb_background;
+ else if (rwb->wc && !wb_recent_wait(rwb))
limit = 0;
else
limit = rwb->wb_normal;
@@ -483,6 +488,9 @@ static inline unsigned int get_limit(struct rq_wb *rwb, unsigned long rw)
{
unsigned int limit;
+ if ((rw & REQ_OP_MASK) == REQ_OP_DISCARD)
+ return rwb->wb_background;
+
/*
* At this point we know it's a buffered write. If this is
* kswapd trying to free memory, or REQ_SYNC is set, then
@@ -564,21 +572,20 @@ static void __wbt_wait(struct rq_wb *rwb, enum wbt_flags wb_acct,
static inline bool wbt_should_throttle(struct rq_wb *rwb, struct bio *bio)
{
- const int op = bio_op(bio);
-
- /*
- * If not a WRITE, do nothing
- */
- if (op != REQ_OP_WRITE)
- return false;
-
- /*
- * Don't throttle WRITE_ODIRECT
- */
- if ((bio->bi_opf & (REQ_SYNC | REQ_IDLE)) == (REQ_SYNC | REQ_IDLE))
+ switch (bio_op(bio)) {
+ case REQ_OP_WRITE:
+ /*
+ * Don't throttle WRITE_ODIRECT
+ */
+ if ((bio->bi_opf & (REQ_SYNC | REQ_IDLE)) ==
+ (REQ_SYNC | REQ_IDLE))
+ return false;
+ /* fallthrough */
+ case REQ_OP_DISCARD:
+ return true;
+ default:
return false;
-
- return true;
+ }
}
/*
@@ -605,6 +612,8 @@ enum wbt_flags wbt_wait(struct rq_wb *rwb, struct bio *bio, spinlock_t *lock)
if (current_is_kswapd())
ret |= WBT_KSWAPD;
+ if (bio_op(bio) == REQ_OP_DISCARD)
+ ret |= WBT_DISCARD;
__wbt_wait(rwb, ret, bio->bi_opf, lock);
diff --git a/block/blk-wbt.h b/block/blk-wbt.h
index 8038b4a0d4ef..d6a125e49db5 100644
--- a/block/blk-wbt.h
+++ b/block/blk-wbt.h
@@ -14,13 +14,15 @@ enum wbt_flags {
WBT_TRACKED = 1, /* write, tracked for throttling */
WBT_READ = 2, /* read */
WBT_KSWAPD = 4, /* write, from kswapd */
+ WBT_DISCARD = 8, /* discard */
- WBT_NR_BITS = 3, /* number of bits */
+ WBT_NR_BITS = 4, /* number of bits */
};
enum {
WBT_RWQ_BG = 0,
WBT_RWQ_KSWAPD,
+ WBT_RWQ_DISCARD,
WBT_NUM_RWQ,
};
--
2.16.4