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authorOmar Sandoval <osandov@fb.com>2018-09-22 02:44:34 +0300
committerJens Axboe <axboe@kernel.dk>2018-09-22 05:26:59 +0300
commitb57e99b4b8b0ebdf9707424e7ddc0c392bdc5fe6 (patch)
tree403679b552a10c8258d4375c561421b367504781 /block/blk-core.c
parentd611aaf336b2e8e81f98490eabf7b92889b15319 (diff)
downloadlinux-b57e99b4b8b0ebdf9707424e7ddc0c392bdc5fe6.tar.xz
block: use nanosecond resolution for iostat
Klaus Kusche reported that the I/O busy time in /proc/diskstats was not updating properly on 4.18. This is because we started using ktime to track elapsed time, and we convert nanoseconds to jiffies when we update the partition counter. However, this gets rounded down, so any I/Os that take less than a jiffy are not accounted for. Previously in this case, the value of jiffies would sometimes increment while we were doing I/O, so at least some I/Os were accounted for. Let's convert the stats to use nanoseconds internally. We still report milliseconds as before, now more accurately than ever. The value is still truncated to 32 bits for backwards compatibility. Fixes: 522a777566f5 ("block: consolidate struct request timestamp fields") Cc: stable@vger.kernel.org Reported-by: Klaus Kusche <klaus.kusche@computerix.info> Signed-off-by: Omar Sandoval <osandov@fb.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/blk-core.c')
-rw-r--r--block/blk-core.c4
1 files changed, 1 insertions, 3 deletions
diff --git a/block/blk-core.c b/block/blk-core.c
index 4dbc93f43b38..cff0a60ee200 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -2733,17 +2733,15 @@ void blk_account_io_done(struct request *req, u64 now)
* containing request is enough.
*/
if (blk_do_io_stat(req) && !(req->rq_flags & RQF_FLUSH_SEQ)) {
- unsigned long duration;
const int sgrp = op_stat_group(req_op(req));
struct hd_struct *part;
int cpu;
- duration = nsecs_to_jiffies(now - req->start_time_ns);
cpu = part_stat_lock();
part = req->part;
part_stat_inc(cpu, part, ios[sgrp]);
- part_stat_add(cpu, part, ticks[sgrp], duration);
+ part_stat_add(cpu, part, nsecs[sgrp], now - req->start_time_ns);
part_round_stats(req->q, cpu, part);
part_dec_in_flight(req->q, part, rq_data_dir(req));