workqueue: update sysfs interface to reflect NUMA awareness and a kernel param to disable NUMA affinity

Unbound workqueues are now NUMA aware.  Let's add some control knobs
and update sysfs interface accordingly.

* Add kernel param workqueue.numa_disable which disables NUMA affinity
  globally.

* Replace sysfs file "pool_id" with "pool_ids" which contain
  node:pool_id pairs.  This change is userland-visible but "pool_id"
  hasn't seen a release yet, so this is okay.

* Add a new sysf files "numa" which can toggle NUMA affinity on
  individual workqueues.  This is implemented as attrs->no_numa whichn
  is special in that it isn't part of a pool's attributes.  It only
  affects how apply_workqueue_attrs() picks which pools to use.

After "pool_ids" change, first_pwq() doesn't have any user left.
Removed.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 4609e81dbc37..c75ea0b8ec59 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3222,6 +3222,15 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                         or other driver-specific files in the
                         Documentation/watchdog/ directory.
 
+        workqueue.disable_numa
+                        By default, all work items queued to unbound
+                        workqueues are affine to the NUMA nodes they're
+                        issued on, which results in better behavior in
+                        general.  If NUMA affinity needs to be disabled for
+                        whatever reason, this option can be used.  Note
+                        that this also can be controlled per-workqueue for
+                        workqueues visible under /sys/bus/workqueue/.
+
         x2apic_phys     [X86-64,APIC] Use x2apic physical mode instead of
                         default x2apic cluster mode on platforms
                         supporting x2apic.