On 16.06.23 11:21, lipeifeng@xxxxxxxx wrote:
>> From: lipeifeng <lipeifeng@xxxxxxxx>
>>
>> Some of shrinkers during shrink_slab would enter synchronous-wait due
>> to lock or other reasons, which would causes kswapd or direct_reclaim
>> to be blocked.
>>
>> This patch export shrink_slab so that it can be called in drivers
>> which can shrink memory independently.
>>
>> Signed-off-by: lipeifeng <lipeifeng@xxxxxxxx>
>> ---
>> mm/vmscan.c | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/mm/vmscan.c b/mm/vmscan.c index
>> 6d0cd2840cf0..2e54fa52e7ec 100644
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -1043,7 +1043,7 @@ static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid,
>> *
>> * Returns the number of reclaimed slab objects.
>> */
>> -static unsigned long shrink_slab(gfp_t gfp_mask, int nid,
>> +unsigned long shrink_slab(gfp_t gfp_mask, int nid,
>> struct mem_cgroup *memcg,
>> int priority)
>> {
>> @@ -1087,6 +1087,7 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid,
>> cond_resched();
>> return freed;
>> }
>> +EXPORT_SYMBOL_GPL(shrink_slab);
>>
>> static unsigned long drop_slab_node(int nid)
>> {
>
>It feels like something we don't want arbitrary drivers to call.
>
>Unrelated to that, this better be sent along with actual driver usage.
Hi Sir：
Virtually, we have implemented async shrink_slabd isolated from kswapd and direct_reclaim.
The goal above it is to avoid the sync-wait in kswapd or direct_reclaim due to some shrinkers.
But the async shrink_slabd was only applied to mobile products so that I didn't make sure any
risk in other products. For the above reasons, I wanna merge the patch to export shrink_slab
and the patch of drivers would be considered to be pushed if I check all the risks.
Some informal code files of driver are attached for your reference.
-----邮件原件-----
发件人: David Hildenbrand <david@xxxxxxxxxx>
发送时间: 2023年6月16日 17:43
收件人: 李培锋(wink) <lipeifeng@xxxxxxxx>; akpm@xxxxxxxxxxxxxxxxxxxx
抄送: linux-mm@xxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; surenb@xxxxxxxxxx; gregkh@xxxxxxxxxx
主题: Re: [PATCH] mm: vmscan: export func:shrink_slab
On 16.06.23 11:21, lipeifeng@xxxxxxxx wrote:
> From: lipeifeng <lipeifeng@xxxxxxxx>
>
> Some of shrinkers during shrink_slab would enter synchronous-wait due
> to lock or other reasons, which would causes kswapd or direct_reclaim
> to be blocked.
>
> This patch export shrink_slab so that it can be called in drivers
> which can shrink memory independently.
>
> Signed-off-by: lipeifeng <lipeifeng@xxxxxxxx>
> ---
> mm/vmscan.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c index
> 6d0cd2840cf0..2e54fa52e7ec 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1043,7 +1043,7 @@ static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid,
> *
> * Returns the number of reclaimed slab objects.
> */
> -static unsigned long shrink_slab(gfp_t gfp_mask, int nid,
> +unsigned long shrink_slab(gfp_t gfp_mask, int nid,
> struct mem_cgroup *memcg,
> int priority)
> {
> @@ -1087,6 +1087,7 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid,
> cond_resched();
> return freed;
> }
> +EXPORT_SYMBOL_GPL(shrink_slab);
>
> static unsigned long drop_slab_node(int nid)
> {
It feels like something we don't want arbitrary drivers to call.
Unrelated to that, this better be sent along with actual driver usage.
--
Cheers,
David / dhildenb
// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2020-2022 Oplus. All rights reserved.
*/
#define pr_fmt(fmt) "shrink_async: " fmt
#include <linux/module.h>
#include <trace/hooks/vmscan.h>
#include <linux/swap.h>
#include <linux/proc_fs.h>
#include <linux/gfp.h>
#include <linux/types.h>
#include <linux/cpufreq.h>
#include <linux/freezer.h>
#include <linux/wait.h>
#define SHRINK_SLABD_NAME "kshrink_slabd"
extern unsigned long shrink_slab(gfp_t gfp_mask, int nid,
struct mem_cgroup *memcg,
int priority);
static int kshrink_slabd_pid;
static struct task_struct *shrink_slabd_tsk = NULL;
static bool async_shrink_slabd_setup = false;
wait_queue_head_t shrink_slabd_wait;
struct async_slabd_parameter {
struct mem_cgroup *shrink_slabd_memcg;
gfp_t shrink_slabd_gfp_mask;
atomic_t shrink_slabd_runnable;
int shrink_slabd_nid;
int priority;
} asp;
static struct reclaim_state async_reclaim_state = {
.reclaimed_slab = 0,
};
static bool is_shrink_slabd_task(struct task_struct *tsk)
{
return tsk->pid == kshrink_slabd_pid;
}
bool wakeup_shrink_slabd(gfp_t gfp_mask, int nid,
struct mem_cgroup *memcg,
int priority)
{
if (unlikely(!async_shrink_slabd_setup))
return false;
if (atomic_read(&(asp.shrink_slabd_runnable)) == 1)
return true;
current->reclaim_state = &async_reclaim_state;
asp.shrink_slabd_gfp_mask = gfp_mask;
asp.shrink_slabd_nid = nid;
asp.shrink_slabd_memcg = memcg;
asp.priority = priority;
atomic_set(&(asp.shrink_slabd_runnable), 1);
wake_up_interruptible(&shrink_slabd_wait);
return true;
}
void set_async_slabd_cpus(void)
{
struct cpumask mask;
struct cpumask *cpumask = &mask;
pg_data_t *pgdat = NODE_DATA(0);
unsigned int cpu = 0, cpufreq_max_tmp = 0;
struct cpufreq_policy *policy_max;
static bool set_slabd_cpus_success = false;
if (unlikely(!async_shrink_slabd_setup))
return;
if (likely(set_slabd_cpus_success))
return;
for_each_possible_cpu(cpu) {
struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
if (policy == NULL)
continue;
if (policy->cpuinfo.max_freq >= cpufreq_max_tmp) {
cpufreq_max_tmp = policy->cpuinfo.max_freq;
policy_max = policy;
}
}
cpumask_copy(cpumask, cpumask_of_node(pgdat->node_id));
cpumask_andnot(cpumask, cpumask, policy_max->related_cpus);
if (!cpumask_empty(cpumask)) {
set_cpus_allowed_ptr(shrink_slabd_tsk, cpumask);
set_slabd_cpus_success = true;
}
}
static int kshrink_slabd_func(void *p)
{
struct mem_cgroup *memcg;
gfp_t gfp_mask;
int nid, priority;
/*
* Tell the memory management that we're a "memory allocator",
* and that if we need more memory we should get access to it
* regardless (see "__alloc_pages()"). "kswapd" should
* never get caught in the normal page freeing logic.
*
* (Kswapd normally doesn't need memory anyway, but sometimes
* you need a small amount of memory in order to be able to
* page out something else, and this flag essentially protects
* us from recursively trying to free more memory as we're
* trying to free the first piece of memory in the first place).
*/
current->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
set_freezable();
current->reclaim_state = &async_reclaim_state;
asp.shrink_slabd_gfp_mask = 0;
asp.shrink_slabd_nid = 0;
asp.shrink_slabd_memcg = NULL;
atomic_set(&(asp.shrink_slabd_runnable), 0);
asp.priority = 0;
while (!kthread_should_stop()) {
wait_event_freezable(shrink_slabd_wait,
(atomic_read(&(asp.shrink_slabd_runnable)) == 1));
set_async_slabd_cpus();
nid = asp.shrink_slabd_nid;
gfp_mask = asp.shrink_slabd_gfp_mask;
priority = asp.priority;
memcg = asp.shrink_slabd_memcg;
shrink_slab(gfp_mask, nid, memcg, priority);
atomic_set(&(asp.shrink_slabd_runnable), 0);
}
current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD);
current->reclaim_state = NULL;
return 0;
}
static void should_shrink_async(void *data, gfp_t gfp_mask, int nid,
struct mem_cgroup *memcg, int priority, bool *bypass)
{
if (unlikely(!async_shrink_slabd_setup)) {
*bypass = false;
return;
}
if (is_shrink_slabd_task(current)) {
*bypass = false;
} else {
*bypass = true;
wakeup_shrink_slabd(gfp_mask, nid, memcg, priority);
}
}
static int register_shrink_async_vendor_hooks(void)
{
int ret = 0;
ret = register_trace_android_vh_shrink_slab_bypass(should_shrink_async, NULL);
if (ret != 0) {
pr_err("register_trace_android_vh_shrink_slab_bypass failed! ret=%d\n", ret);
goto out;
}
out:
return ret;
}
static void unregister_shrink_async_vendor_hooks(void)
{
unregister_trace_android_vh_shrink_slab_bypass(should_shrink_async, NULL);
return;
}
static int __init shrink_async_init(void)
{
int ret = 0;
ret = register_shrink_async_vendor_hooks();
if (ret != 0)
return ret;
init_waitqueue_head(&shrink_slabd_wait);
shrink_slabd_tsk = kthread_run(kshrink_slabd_func, NULL, SHRINK_SLABD_NAME);
if (IS_ERR_OR_NULL(shrink_slabd_tsk)) {
pr_err("Failed to start shrink_slabd on node 0\n");
ret = PTR_ERR(shrink_slabd_tsk);
shrink_slabd_tsk = NULL;
return ret;
}
kshrink_slabd_pid = shrink_slabd_tsk->pid;
async_shrink_slabd_setup = true;
pr_info("kshrink_async succeed!\n");
return 0;
}
static void __exit shrink_async_exit(void)
{
unregister_shrink_async_vendor_hooks();
pr_info("shrink_async exit succeed!\n");
return;
}
module_init(shrink_async_init);
module_exit(shrink_async_exit);
MODULE_LICENSE("GPL v2");
