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Subject[PATCH 4/7 V2] workqueue: reuse the current per-node pwq when its attrs unchanged
Date
If the cpuamsk is changed, it is possible that only a part of the per-node
pwq is affected. This can happen when the user changes the cpumask of
a workqueue or the low level cpumask.

So we try to reuse the current per-node pwq when its attrs unchanged.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
---
kernel/workqueue.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 0fa352d..24e5fe4 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -3552,6 +3552,7 @@ apply_wqattrs_prepare(struct workqueue_struct *wq,
{
struct apply_wqattrs_ctx *ctx;
struct workqueue_attrs *new_attrs, *tmp_attrs;
+ struct pool_workqueue *pwq;
int node;

lockdep_assert_held(&wq_pool_mutex);
@@ -3592,9 +3593,14 @@ apply_wqattrs_prepare(struct workqueue_struct *wq,

for_each_node(node) {
if (wq_calc_node_cpumask(new_attrs, node, -1, tmp_attrs->cpumask)) {
- ctx->pwq_tbl[node] = alloc_unbound_pwq(wq, tmp_attrs);
- if (!ctx->pwq_tbl[node])
+ pwq = unbound_pwq_by_node(wq, node);
+ if (pwq && wqattrs_equal(tmp_attrs, pwq->pool->attrs))
+ pwq = get_pwq_unlocked(pwq);
+ else
+ pwq = alloc_unbound_pwq(wq, tmp_attrs);
+ if (!pwq)
goto out_free;
+ ctx->pwq_tbl[node] = pwq;
} else {
ctx->dfl_pwq->refcnt++;
ctx->pwq_tbl[node] = ctx->dfl_pwq;
@@ -3739,7 +3745,6 @@ static void wq_update_unbound_numa(struct workqueue_struct *wq, int cpu,
cpumask = target_attrs->cpumask;

copy_workqueue_attrs(target_attrs, wq->unbound_attrs);
- pwq = unbound_pwq_by_node(wq, node);

/*
* Let's determine what needs to be done. If the target cpumask is
@@ -3748,6 +3753,7 @@ static void wq_update_unbound_numa(struct workqueue_struct *wq, int cpu,
* equals the default pwq's, the default pwq should be used.
*/
if (wq_calc_node_cpumask(wq->dfl_pwq->pool->attrs, node, cpu_off, cpumask)) {
+ pwq = unbound_pwq_by_node(wq, node);
if (cpumask_equal(cpumask, pwq->pool->attrs->cpumask))
return;
} else {
--
2.1.0


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