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blk-wbt: don't throttle swap writes in direct reclaim

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Now we avoid throttling swap writes by determining whether the current
process is kswapd (aka current_is_kswapd()), but swap writes can come
from either kswapd or direct reclaim, so the swap writes from direct
reclaim will still be throttled.

When a process holds a lock to allocate a free page, and enters direct
reclaim because there is no free memory, then it might trigger a hung
due to the wbt throttling that causes other processes to fail to get
the lock.

Both kswapd and direct reclaim set the REQ_SWAP flag, so use REQ_SWAP
instead of current_is_kswapd() to avoid throttling swap writes. Also
renamed WBT_KSWAPD to WBT_SWAP and WBT_RWQ_KSWAPD to WBT_RWQ_SWAP.

Signed-off-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20240604030522.3686177-1-libaokun@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Baokun Li 2024-06-04 11:05:22 +08:00 committed by Jens Axboe
parent 62e35f9422
commit 4e63aeb5d0
1 changed files with 9 additions and 9 deletions
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18
block/blk-wbt.c
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@ -37,7 +37,7 @@
enum wbt_flags { enum wbt_flags {
WBT_TRACKED = 1, /* write, tracked for throttling */ WBT_TRACKED = 1, /* write, tracked for throttling */
WBT_READ = 2, /* read */ WBT_READ = 2, /* read */
WBT_KSWAPD = 4, /* write, from kswapd */ WBT_SWAP = 4, /* write, from swap_writepage() */
WBT_DISCARD = 8, /* discard */ WBT_DISCARD = 8, /* discard */
WBT_NR_BITS = 4, /* number of bits */ WBT_NR_BITS = 4, /* number of bits */
@ -45,7 +45,7 @@ enum wbt_flags {
enum { enum {
WBT_RWQ_BG = 0, WBT_RWQ_BG = 0,
WBT_RWQ_KSWAPD, WBT_RWQ_SWAP,
WBT_RWQ_DISCARD, WBT_RWQ_DISCARD,
WBT_NUM_RWQ, WBT_NUM_RWQ,
}; };
@ -172,8 +172,8 @@ static bool wb_recent_wait(struct rq_wb *rwb)
static inline struct rq_wait *get_rq_wait(struct rq_wb *rwb, static inline struct rq_wait *get_rq_wait(struct rq_wb *rwb,
enum wbt_flags wb_acct) enum wbt_flags wb_acct)
{ {
if (wb_acct & WBT_KSWAPD) if (wb_acct & WBT_SWAP)
return &rwb->rq_wait[WBT_RWQ_KSWAPD]; return &rwb->rq_wait[WBT_RWQ_SWAP];
else if (wb_acct & WBT_DISCARD) else if (wb_acct & WBT_DISCARD)
return &rwb->rq_wait[WBT_RWQ_DISCARD]; return &rwb->rq_wait[WBT_RWQ_DISCARD];
@ -528,7 +528,7 @@ static bool close_io(struct rq_wb *rwb)
time_before(now, rwb->last_comp + HZ / 10); time_before(now, rwb->last_comp + HZ / 10);
} }
#define REQ_HIPRIO (REQ_SYNC | REQ_META | REQ_PRIO) #define REQ_HIPRIO (REQ_SYNC | REQ_META | REQ_PRIO | REQ_SWAP)
static inline unsigned int get_limit(struct rq_wb *rwb, blk_opf_t opf) static inline unsigned int get_limit(struct rq_wb *rwb, blk_opf_t opf)
{ {
@ -539,13 +539,13 @@ static inline unsigned int get_limit(struct rq_wb *rwb, blk_opf_t opf)
/* /*
* At this point we know it's a buffered write. If this is * At this point we know it's a buffered write. If this is
* kswapd trying to free memory, or REQ_SYNC is set, then * swap trying to free memory, or REQ_SYNC is set, then
* it's WB_SYNC_ALL writeback, and we'll use the max limit for * it's WB_SYNC_ALL writeback, and we'll use the max limit for
* that. If the write is marked as a background write, then use * that. If the write is marked as a background write, then use
* the idle limit, or go to normal if we haven't had competing * the idle limit, or go to normal if we haven't had competing
* IO for a bit. * IO for a bit.
*/ */
if ((opf & REQ_HIPRIO) || wb_recent_wait(rwb) || current_is_kswapd()) if ((opf & REQ_HIPRIO) || wb_recent_wait(rwb))
limit = rwb->rq_depth.max_depth; limit = rwb->rq_depth.max_depth;
else if ((opf & REQ_BACKGROUND) || close_io(rwb)) { else if ((opf & REQ_BACKGROUND) || close_io(rwb)) {
/* /*
@ -622,8 +622,8 @@ static enum wbt_flags bio_to_wbt_flags(struct rq_wb *rwb, struct bio *bio)
if (bio_op(bio) == REQ_OP_READ) { if (bio_op(bio) == REQ_OP_READ) {
flags = WBT_READ; flags = WBT_READ;
} else if (wbt_should_throttle(bio)) { } else if (wbt_should_throttle(bio)) {
if (current_is_kswapd()) if (bio->bi_opf & REQ_SWAP)
flags |= WBT_KSWAPD; flags |= WBT_SWAP;
if (bio_op(bio) == REQ_OP_DISCARD) if (bio_op(bio) == REQ_OP_DISCARD)
flags |= WBT_DISCARD; flags |= WBT_DISCARD;
flags |= WBT_TRACKED; flags |= WBT_TRACKED;