]> git.baikalelectronics.ru Git - kernel.git/commit
drm/i915: Do not sync RCU during shrinking
authorJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Wed, 10 May 2017 11:00:40 +0000 (14:00 +0300)
committerJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Thu, 11 May 2017 12:58:23 +0000 (15:58 +0300)
commit84ffe0cdaf1df692454e413e4835d131c688f7e9
tree92d55e3acb1738d8a8653581ee5b6ba775b2d754
parent5b1aff8ac1d3bd6412b9fb2b11065f9719a58b40
drm/i915: Do not sync RCU during shrinking

Due to the complex dependencies between workqueues and RCU, which
are not easily detected by lockdep, do not synchronize RCU during
shrinking.

On low-on-memory systems (mem=1G for example), the RCU sync leads
to all system workqueus freezing and unrelated lockdep splats are
displayed according to reports. GIT bisecting done by J. R.
Okajima points to the commit where RCU syncing was extended.

RCU sync gains us very little benefit in real life scenarios
where the amount of memory used by object backing storage is
dominant over the metadata under RCU, so drop it altogether.

 " Yeeeaah, if core could just, go ahead and reclaim RCU
   queues, that'd be great. "

  - Chris Wilson, 2016 (3695f0bffa8f)

v2: More information to commit message.
v3: Remove "grep _rcu_" escapee from i915_gem_shrink_all (Andrea)

Fixes: af5ca7ef6760 ("drm/i915: Don't call synchronize_rcu_expedited under struct_mutex")
Suggested-by: Chris Wilson <chris@chris-wilson.co.uk>
Reported-by: J. R. Okajima <hooanon05g@gmail.com>
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Tested-by: Hugh Dickins <hughd@google.com>
Tested-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: J. R. Okajima <hooanon05g@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: <stable@vger.kernel.org> # v4.11+
Link: http://patchwork.freedesktop.org/patch/msgid/1494414040-11160-1-git-send-email-joonas.lahtinen@linux.intel.com
drivers/gpu/drm/i915/i915_gem_shrinker.c