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author | Jens Axboe <axboe@kernel.dk> | 2020-07-13 15:48:16 -0600 |
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committer | Jens Axboe <axboe@kernel.dk> | 2020-07-15 09:23:35 -0600 |
commit | 9054650fac24b784df8500aba2869ebf240d069a (patch) | |
tree | 46ae23f1a8065541a9a0f3649fc38e57c8ba1c07 | |
parent | 87890092ee6504a49841d854ff81a71a85c19a5d (diff) | |
download | linux-9054650fac24b784df8500aba2869ebf240d069a.tar.gz linux-9054650fac24b784df8500aba2869ebf240d069a.tar.bz2 linux-9054650fac24b784df8500aba2869ebf240d069a.zip |
block: relax jiffies rounding for timeouts
In doing high IOPS testing, blk-mq is generally pretty well optimized.
There are a few things that stuck out as using more CPU than what is
really warranted, and one thing is the round_jiffies_up() that we do
twice for each request. That accounts for about 0.8% of the CPU in
my testing.
We can make this cheaper by avoiding an integer division, by just adding
a rough HZ mask that we can AND with instead. The timeouts are only on a
second granularity already, we don't have to be that accurate here and
this patch barely changes that. All we care about is nice grouping.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
-rw-r--r-- | block/blk-timeout.c | 22 |
1 files changed, 20 insertions, 2 deletions
diff --git a/block/blk-timeout.c b/block/blk-timeout.c index 3a1ac6434758..8ab8a82825cd 100644 --- a/block/blk-timeout.c +++ b/block/blk-timeout.c @@ -88,11 +88,29 @@ void blk_abort_request(struct request *req) } EXPORT_SYMBOL_GPL(blk_abort_request); +static unsigned long blk_timeout_mask __read_mostly; + +int __init blk_timeout_init(void) +{ + blk_timeout_mask = roundup_pow_of_two(HZ) - 1; + return 0; +} + +late_initcall(blk_timeout_init); + +/* + * Just a rough estimate, we don't care about specific values for timeouts. + */ +static inline unsigned long blk_round_jiffies(unsigned long j) +{ + return (j + blk_timeout_mask) + 1; +} + unsigned long blk_rq_timeout(unsigned long timeout) { unsigned long maxt; - maxt = round_jiffies_up(jiffies + BLK_MAX_TIMEOUT); + maxt = blk_round_jiffies(jiffies + BLK_MAX_TIMEOUT); if (time_after(timeout, maxt)) timeout = maxt; @@ -129,7 +147,7 @@ void blk_add_timer(struct request *req) * than an existing one, modify the timer. Round up to next nearest * second. */ - expiry = blk_rq_timeout(round_jiffies_up(expiry)); + expiry = blk_rq_timeout(blk_round_jiffies(expiry)); if (!timer_pending(&q->timeout) || time_before(expiry, q->timeout.expires)) { |