| Message ID | 1415194550-121498-1-git-send-email-hare@suse.de (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Delegated to: | Mike Snitzer |
| Headers | show |
On Wed, Nov 05 2014 at 8:35am -0500, Hannes Reinecke <hare@suse.de> wrote: > When creating new devices dm_sync_table() calls > synchronize_rcu_expedited(), causing _all_ pending > RCU pointers to be flushed. This causes a latency > overhead especially noticeable when creating lots > of devices. > And all of this is pointless as there are no old > maps to be disconnected, and hence no stale pointers > which would need to be cleared up. > > Signed-off-by: Hannes Reinecke <hare@suse.de> Looks good, I'll get it staged for 3.19 (will need to be rebased on the linux-dm.git 'dm-for-3.19' branch given the suspend related refactoring there, but I'll take care of it as needed). -- dm-devel mailing list dm-devel@redhat.com https://www.redhat.com/mailman/listinfo/dm-devel
On Wed, 5 Nov 2014, Hannes Reinecke wrote: > When creating new devices dm_sync_table() calls > synchronize_rcu_expedited(), causing _all_ pending > RCU pointers to be flushed. This causes a latency > overhead especially noticeable when creating lots > of devices. > And all of this is pointless as there are no old > maps to be disconnected, and hence no stale pointers > which would need to be cleared up. > > Signed-off-by: Hannes Reinecke <hare@suse.de> Reviewed-by: Mikulas Patocka <mpatocka@redhat.com> > --- > drivers/md/dm.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/drivers/md/dm.c b/drivers/md/dm.c > index 58f3927..2c2c6cf 100644 > --- a/drivers/md/dm.c > +++ b/drivers/md/dm.c > @@ -2341,7 +2341,8 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t, > set_bit(DMF_MERGE_IS_OPTIONAL, &md->flags); > else > clear_bit(DMF_MERGE_IS_OPTIONAL, &md->flags); > - dm_sync_table(md); > + if (old_map) > + dm_sync_table(md); > > return old_map; > } > @@ -2782,7 +2783,8 @@ int dm_suspend(struct mapped_device *md, unsigned suspend_flags) > * flush_workqueue(md->wq). > */ > set_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags); > - synchronize_srcu(&md->io_barrier); > + if (map) > + synchronize_srcu(&md->io_barrier); > > /* > * Stop md->queue before flushing md->wq in case request-based > @@ -2802,7 +2804,8 @@ int dm_suspend(struct mapped_device *md, unsigned suspend_flags) > > if (noflush) > clear_bit(DMF_NOFLUSH_SUSPENDING, &md->flags); > - synchronize_srcu(&md->io_barrier); > + if (map) > + synchronize_srcu(&md->io_barrier); > > /* were we interrupted ? */ > if (r < 0) { > -- > 1.8.5.2 > > -- > dm-devel mailing list > dm-devel@redhat.com > https://www.redhat.com/mailman/listinfo/dm-devel > -- dm-devel mailing list dm-devel@redhat.com https://www.redhat.com/mailman/listinfo/dm-devel
diff --git a/drivers/md/dm.c b/drivers/md/dm.c index 58f3927..2c2c6cf 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -2341,7 +2341,8 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t, set_bit(DMF_MERGE_IS_OPTIONAL, &md->flags); else clear_bit(DMF_MERGE_IS_OPTIONAL, &md->flags); - dm_sync_table(md); + if (old_map) + dm_sync_table(md); return old_map; } @@ -2782,7 +2783,8 @@ int dm_suspend(struct mapped_device *md, unsigned suspend_flags) * flush_workqueue(md->wq). */ set_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags); - synchronize_srcu(&md->io_barrier); + if (map) + synchronize_srcu(&md->io_barrier); /* * Stop md->queue before flushing md->wq in case request-based @@ -2802,7 +2804,8 @@ int dm_suspend(struct mapped_device *md, unsigned suspend_flags) if (noflush) clear_bit(DMF_NOFLUSH_SUSPENDING, &md->flags); - synchronize_srcu(&md->io_barrier); + if (map) + synchronize_srcu(&md->io_barrier); /* were we interrupted ? */ if (r < 0) {
When creating new devices dm_sync_table() calls synchronize_rcu_expedited(), causing _all_ pending RCU pointers to be flushed. This causes a latency overhead especially noticeable when creating lots of devices. And all of this is pointless as there are no old maps to be disconnected, and hence no stale pointers which would need to be cleared up. Signed-off-by: Hannes Reinecke <hare@suse.de> --- drivers/md/dm.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)