On Thu, 29 Nov 2018, Mike Snitzer wrote: > On Tue, Nov 27 2018 at 7:42pm -0500, > Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote: > > > Now when part_round_stats is gone, we can switch to per-cpu in-flight > > counters. > > > > We use the local-atomic type local_t, so that if part_inc_in_flight or > > part_dec_in_flight is reentrantly called from an interrupt, the value will > > be correct. > > > > The other counters could be corrupted due to reentrant interrupt, but the > > corruption only results in slight counter skew - the in_flight counter > > must be exact, so it needs local_t. > > > > Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx> > > > > --- > > block/bio.c | 4 ++-- > > block/blk-core.c | 4 ++-- > > block/blk-merge.c | 2 +- > > block/genhd.c | 47 +++++++++++++++++++++++++++++++++++------------ > > drivers/md/dm.c | 4 +--- > > include/linux/genhd.h | 7 ++++--- > > 6 files changed, 45 insertions(+), 23 deletions(-) > > > ... > > Index: linux-block/drivers/md/dm.c > > =================================================================== > > --- linux-block.orig/drivers/md/dm.c 2018-11-28 00:09:59.000000000 +0100 > > +++ linux-block/drivers/md/dm.c 2018-11-28 00:09:59.000000000 +0100 > > @@ -663,8 +663,7 @@ static void start_io_acct(struct dm_io * > > generic_start_io_acct(md->queue, bio_op(bio), bio_sectors(bio), > > &dm_disk(md)->part0); > > > > - atomic_set(&dm_disk(md)->part0.in_flight[rw], > > - atomic_inc_return(&md->pending[rw])); > > + atomic_inc(&md->pending[rw]); > > > > if (unlikely(dm_stats_used(&md->stats))) > > dm_stats_account_io(&md->stats, bio_data_dir(bio), > > @@ -693,7 +692,6 @@ static void end_io_acct(struct dm_io *io > > * a flush. > > */ > > pending = atomic_dec_return(&md->pending[rw]); > > - atomic_set(&dm_disk(md)->part0.in_flight[rw], pending); > > pending += atomic_read(&md->pending[rw^0x1]); > > > > /* nudge anyone waiting on suspend queue */ > > > > > These dm.c hunks conflict with changes from you that I already staged in > dm-4.21, see: > > https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-4.21&id=b5616f7a11592cc74860f4ec3e3c4fba6688eefa > https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-4.21&id=78f95b53c203c969bbe6b86e405f7a891a43b6be > > I'd really like to get away from DM maintaining its own ->pending > counters. > > Mike I know. It depends on whether Jens takes these patches or not. If he doesn't take them, dm will use percpu counters on its own and it will return zero in the "/sys/block/dm-*/inflight" file. Mikulas
