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| author | Mike Snitzer <snitzer@redhat.com> | 2017-02-16 23:57:17 -0500 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-03-12 00:41:44 -0500 |
| commit | b7f874eedc9308a43b0d29e2a12f848be724fca7 (patch) | |
| tree | b7f00e19006f3709066058abf7ea6bb83322a744 /drivers/md/dm-raid.c | |
| parent | bad6c16b81b68d81e95ada246649dacc3cdd5e1d (diff) | |
dm round robin: revert "use percpu 'repeat_count' and 'current_path'"
commit 37a098e9d10db6e2efc05fe61e3a6ff2e9802c53 upstream.
The sloppy nature of lockless access to percpu pointers
(s->current_path) in rr_select_path(), from multiple threads, is
causing some paths to used more than others -- which results in less
IO performance being observed.
Revert these upstream commits to restore truly symmetric round-robin
IO submission in DM multipath:
b0b477c dm round robin: use percpu 'repeat_count' and 'current_path'
802934b dm round robin: do not use this_cpu_ptr() without having preemption disabled
There is no benefit to all this complexity if repeat_count = 1 (which is
the recommended default).
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/md/dm-raid.c')
0 files changed, 0 insertions, 0 deletions