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authorPaolo Valente <paolo.valente@linaro.org>2019-03-12 11:59:31 +0300
committerJens Axboe <axboe@kernel.dk>2019-04-01 17:15:40 +0300
commit7074f076ff153021f408229b0ce63063dde9a400 (patch)
tree692007553290b883af2a141ca72890621089fbf8 /block/bfq-iosched.c
parent8cacc5ab3eacf5284bc9b0d7d5b85b748a338104 (diff)
downloadlinux-7074f076ff153021f408229b0ce63063dde9a400.tar.xz
block, bfq: do not tag totally seeky queues as soft rt
Sync random I/O is likely to be confused with soft real-time I/O, because it is characterized by limited throughput and apparently isochronous arrival pattern. To avoid false positives, this commits prevents bfq_queues containing only random (seeky) I/O from being tagged as soft real-time. Tested-by: Holger Hoffstätte <holger@applied-asynchrony.com> Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/bfq-iosched.c')
-rw-r--r--block/bfq-iosched.c14
1 files changed, 14 insertions, 0 deletions
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index b957e9db87d8..7044da0b1c52 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -242,6 +242,14 @@ static struct kmem_cache *bfq_pool;
blk_rq_sectors(rq) < BFQQ_SECT_THR_NONROT))
#define BFQQ_CLOSE_THR (sector_t)(8 * 1024)
#define BFQQ_SEEKY(bfqq) (hweight32(bfqq->seek_history) > 19)
+/*
+ * Sync random I/O is likely to be confused with soft real-time I/O,
+ * because it is characterized by limited throughput and apparently
+ * isochronous arrival pattern. To avoid false positives, queues
+ * containing only random (seeky) I/O are prevented from being tagged
+ * as soft real-time.
+ */
+#define BFQQ_TOTALLY_SEEKY(bfqq) (bfqq->seek_history & -1)
/* Min number of samples required to perform peak-rate update */
#define BFQ_RATE_MIN_SAMPLES 32
@@ -1622,6 +1630,7 @@ static void bfq_bfqq_handle_idle_busy_switch(struct bfq_data *bfqd,
*/
in_burst = bfq_bfqq_in_large_burst(bfqq);
soft_rt = bfqd->bfq_wr_max_softrt_rate > 0 &&
+ !BFQQ_TOTALLY_SEEKY(bfqq) &&
!in_burst &&
time_is_before_jiffies(bfqq->soft_rt_next_start) &&
bfqq->dispatched == 0;
@@ -4816,6 +4825,11 @@ bfq_update_io_seektime(struct bfq_data *bfqd, struct bfq_queue *bfqq,
{
bfqq->seek_history <<= 1;
bfqq->seek_history |= BFQ_RQ_SEEKY(bfqd, bfqq->last_request_pos, rq);
+
+ if (bfqq->wr_coeff > 1 &&
+ bfqq->wr_cur_max_time == bfqd->bfq_wr_rt_max_time &&
+ BFQQ_TOTALLY_SEEKY(bfqq))
+ bfq_bfqq_end_wr(bfqq);
}
static void bfq_update_has_short_ttime(struct bfq_data *bfqd,