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Date: Sat, 22 Jun 2024 00:58:10 -0300
From: Leonardo Bras <leobras@...hat.com>
To: Johannes Weiner <hannes@...xchg.org>,
Michal Hocko <mhocko@...nel.org>,
Roman Gushchin <roman.gushchin@...ux.dev>,
Shakeel Butt <shakeel.butt@...ux.dev>,
Muchun Song <muchun.song@...ux.dev>,
Andrew Morton <akpm@...ux-foundation.org>,
Christoph Lameter <cl@...ux.com>,
Pekka Enberg <penberg@...nel.org>,
David Rientjes <rientjes@...gle.com>,
Joonsoo Kim <iamjoonsoo.kim@....com>,
Vlastimil Babka <vbabka@...e.cz>,
Hyeonggon Yoo <42.hyeyoo@...il.com>,
Leonardo Bras <leobras@...hat.com>,
Thomas Gleixner <tglx@...utronix.de>,
Marcelo Tosatti <mtosatti@...hat.com>
Cc: linux-kernel@...r.kernel.org,
cgroups@...r.kernel.org,
linux-mm@...ck.org
Subject: [RFC PATCH v1 2/4] swap: apply new queue_percpu_work_on() interface
Make use of the new qpw_{un,}lock*() and queue_percpu_work_on()
interface to improve performance & latency on PREEMTP_RT kernels.
For functions that may be scheduled in a different cpu, replace
local_{un,}lock*() by qpw_{un,}lock*(), and replace schedule_work_on() by
queue_percpu_work_on(). The same happens for flush_work() and
flush_percpu_work().
The change requires allocation of qpw_structs instead of a work_structs,
and changing parameters of a few functions to include the cpu parameter.
This should bring no relevant performance impact on non-RT kernels:
For functions that may be scheduled in a different cpu, the local_*lock's
this_cpu_ptr() becomes a per_cpu_ptr(smp_processor_id()).
Signed-off-by: Leonardo Bras <leobras@...hat.com>
---
mm/swap.c | 26 +++++++++++++-------------
1 file changed, 13 insertions(+), 13 deletions(-)
diff --git a/mm/swap.c b/mm/swap.c
index 67786cb77130..c1a61b7cd71a 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -28,21 +28,21 @@
#include <linux/memremap.h>
#include <linux/percpu.h>
#include <linux/cpu.h>
#include <linux/notifier.h>
#include <linux/backing-dev.h>
#include <linux/memcontrol.h>
#include <linux/gfp.h>
#include <linux/uio.h>
#include <linux/hugetlb.h>
#include <linux/page_idle.h>
-#include <linux/local_lock.h>
+#include <linux/qpw.h>
#include <linux/buffer_head.h>
#include "internal.h"
#define CREATE_TRACE_POINTS
#include <trace/events/pagemap.h>
/* How many pages do we try to swap or page in/out together? As a power of 2 */
int page_cluster;
const int page_cluster_max = 31;
@@ -758,45 +758,45 @@ void lru_add_drain(void)
local_unlock(&cpu_fbatches.lock);
mlock_drain_local();
}
/*
* It's called from per-cpu workqueue context in SMP case so
* lru_add_drain_cpu and invalidate_bh_lrus_cpu should run on
* the same cpu. It shouldn't be a problem in !SMP case since
* the core is only one and the locks will disable preemption.
*/
-static void lru_add_and_bh_lrus_drain(void)
+static void lru_add_and_bh_lrus_drain(int cpu)
{
- local_lock(&cpu_fbatches.lock);
- lru_add_drain_cpu(smp_processor_id());
- local_unlock(&cpu_fbatches.lock);
+ qpw_lock(&cpu_fbatches.lock, cpu);
+ lru_add_drain_cpu(cpu);
+ qpw_unlock(&cpu_fbatches.lock, cpu);
invalidate_bh_lrus_cpu();
mlock_drain_local();
}
void lru_add_drain_cpu_zone(struct zone *zone)
{
local_lock(&cpu_fbatches.lock);
lru_add_drain_cpu(smp_processor_id());
drain_local_pages(zone);
local_unlock(&cpu_fbatches.lock);
mlock_drain_local();
}
#ifdef CONFIG_SMP
-static DEFINE_PER_CPU(struct work_struct, lru_add_drain_work);
+static DEFINE_PER_CPU(struct qpw_struct, lru_add_drain_qpw);
-static void lru_add_drain_per_cpu(struct work_struct *dummy)
+static void lru_add_drain_per_cpu(struct work_struct *w)
{
- lru_add_and_bh_lrus_drain();
+ lru_add_and_bh_lrus_drain(qpw_get_cpu(w));
}
static bool cpu_needs_drain(unsigned int cpu)
{
struct cpu_fbatches *fbatches = &per_cpu(cpu_fbatches, cpu);
/* Check these in order of likelihood that they're not zero */
return folio_batch_count(&fbatches->lru_add) ||
data_race(folio_batch_count(&per_cpu(lru_rotate.fbatch, cpu))) ||
folio_batch_count(&fbatches->lru_deactivate_file) ||
@@ -882,31 +882,31 @@ static inline void __lru_add_drain_all(bool force_all_cpus)
*
* If the paired barrier is done at any later step, e.g. after the
* loop, CPU #x will just exit at (C) and miss flushing out all of its
* added pages.
*/
WRITE_ONCE(lru_drain_gen, lru_drain_gen + 1);
smp_mb();
cpumask_clear(&has_work);
for_each_online_cpu(cpu) {
- struct work_struct *work = &per_cpu(lru_add_drain_work, cpu);
+ struct qpw_struct *qpw = &per_cpu(lru_add_drain_qpw, cpu);
if (cpu_needs_drain(cpu)) {
- INIT_WORK(work, lru_add_drain_per_cpu);
- queue_work_on(cpu, mm_percpu_wq, work);
+ INIT_QPW(qpw, lru_add_drain_per_cpu, cpu);
+ queue_percpu_work_on(cpu, mm_percpu_wq, qpw);
__cpumask_set_cpu(cpu, &has_work);
}
}
for_each_cpu(cpu, &has_work)
- flush_work(&per_cpu(lru_add_drain_work, cpu));
+ flush_percpu_work(&per_cpu(lru_add_drain_qpw, cpu));
done:
mutex_unlock(&lock);
}
void lru_add_drain_all(void)
{
__lru_add_drain_all(false);
}
#else
@@ -939,21 +939,21 @@ void lru_cache_disable(void)
*
* Since v5.1 kernel, synchronize_rcu() is guaranteed to wait on
* preempt_disable() regions of code. So any CPU which sees
* lru_disable_count = 0 will have exited the critical
* section when synchronize_rcu() returns.
*/
synchronize_rcu_expedited();
#ifdef CONFIG_SMP
__lru_add_drain_all(true);
#else
- lru_add_and_bh_lrus_drain();
+ lru_add_and_bh_lrus_drain(smp_processor_id());
#endif
}
/**
* folios_put_refs - Reduce the reference count on a batch of folios.
* @folios: The folios.
* @refs: The number of refs to subtract from each folio.
*
* Like folio_put(), but for a batch of folios. This is more efficient
* than writing the loop yourself as it will optimise the locks which need
--
2.45.2
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