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authorMikulas Patocka <mpatocka@redhat.com>2018-12-06 11:41:19 -0500
committerJens Axboe <axboe@kernel.dk>2018-12-10 08:30:37 -0700
commit5b18b5a737600fd20ba2045f320d5926ebbf341a (patch)
treefe35e150bf36785dfe3ed8c845e3b043e56f9f90 /block/genhd.c
parent112f158f66cbe25fd561a5dfe9c3826e06abf757 (diff)
downloadlwn-5b18b5a737600fd20ba2045f320d5926ebbf341a.tar.gz
lwn-5b18b5a737600fd20ba2045f320d5926ebbf341a.zip
block: delete part_round_stats and switch to less precise counting
We want to convert to per-cpu in_flight counters. The function part_round_stats needs the in_flight counter every jiffy, it would be too costly to sum all the percpu variables every jiffy, so it must be deleted. part_round_stats is used to calculate two counters - time_in_queue and io_ticks. time_in_queue can be calculated without part_round_stats, by adding the duration of the I/O when the I/O ends (the value is almost as exact as the previously calculated value, except that time for in-progress I/Os is not counted). io_ticks can be approximated by increasing the value when I/O is started or ended and the jiffies value has changed. If the I/Os take less than a jiffy, the value is as exact as the previously calculated value. If the I/Os take more than a jiffy, io_ticks can drift behind the previously calculated value. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/genhd.c')
-rw-r--r--block/genhd.c3
1 files changed, 0 insertions, 3 deletions
diff --git a/block/genhd.c b/block/genhd.c
index 2fe00cf32b93..cdf174d7d329 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1337,9 +1337,6 @@ static int diskstats_show(struct seq_file *seqf, void *v)
disk_part_iter_init(&piter, gp, DISK_PITER_INCL_EMPTY_PART0);
while ((hd = disk_part_iter_next(&piter))) {
- part_stat_lock();
- part_round_stats(gp->queue, hd);
- part_stat_unlock();
part_in_flight(gp->queue, hd, inflight);
seq_printf(seqf, "%4d %7d %s "
"%lu %lu %lu %u "