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Date: Mon, 14 Jun 2021 20:27:21 +0530
From: Charan Teja Kalla <charante@...eaurora.org>
To: akpm@...ux-foundation.org, vbabka@...e.cz, nigupta@...dia.com,
hannes@...xchg.org, corbet@....net, mcgrof@...nel.org,
keescook@...omium.org, yzaikin@...gle.com, aarcange@...hat.com,
cl@...ux.com, xi.fengfei@....com, mchehab+huawei@...nel.org,
andrew.a.klychkov@...il.com, dave.hansen@...ux.intel.com,
bhe@...hat.com, iamjoonsoo.kim@....com, mateusznosek0@...il.com,
sh_def@....com, vinmenon@...eaurora.org
Cc: linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-mm@...ck.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v3 1/2] mm: compaction: support triggering of proactive
compaction by user
Just another ping to have your comments.
Thanks in advance!!
On 6/7/2021 4:08 PM, Charan Teja Kalla wrote:
> A gentle ping.
>
> --Charan
>
> On 5/31/2021 4:24 PM, Charan Teja Reddy wrote:
>> The proactive compaction[1] gets triggered for every 500msec and run
>> compaction on the node for COMPACTION_HPAGE_ORDER (usually order-9)
>> pages based on the value set to sysctl.compaction_proactiveness.
>> Triggering the compaction for every 500msec in search of
>> COMPACTION_HPAGE_ORDER pages is not needed for all applications,
>> especially on the embedded system usecases which may have few MB's of
>> RAM. Enabling the proactive compaction in its state will endup in
>> running almost always on such systems.
>>
>> Other side, proactive compaction can still be very much useful for
>> getting a set of higher order pages in some controllable
>> manner(controlled by using the sysctl.compaction_proactiveness). Thus on
>> systems where enabling the proactive compaction always may proove not
>> required, can trigger the same from user space on write to its sysctl
>> interface. As an example, say app launcher decide to launch the memory
>> heavy application which can be launched fast if it gets more higher
>> order pages thus launcher can prepare the system in advance by
>> triggering the proactive compaction from userspace.
>>
>> This triggering of proactive compaction is done on a write to
>> sysctl.compaction_proactiveness by user.
>>
>> [1]https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit?id=facdaa917c4d5a376d09d25865f5a863f906234a
>>
>> Signed-off-by: Charan Teja Reddy <charante@...eaurora.org>
>> ---
>> changes in V2:
>> - https://lore.kernel.org/patchwork/patch/1431283/
>>
>> changes in V1:
>> - https://lore.kernel.org/lkml/1619098678-8501-1-git-send-email-charante@codeaurora.org/
>>
>> Documentation/admin-guide/sysctl/vm.rst | 3 ++-
>> include/linux/compaction.h | 2 ++
>> include/linux/mmzone.h | 1 +
>> kernel/sysctl.c | 2 +-
>> mm/compaction.c | 44 ++++++++++++++++++++++++++++++---
>> 5 files changed, 47 insertions(+), 5 deletions(-)
>>
>> diff --git a/Documentation/admin-guide/sysctl/vm.rst b/Documentation/admin-guide/sysctl/vm.rst
>> index 586cd4b..5e8097d 100644
>> --- a/Documentation/admin-guide/sysctl/vm.rst
>> +++ b/Documentation/admin-guide/sysctl/vm.rst
>> @@ -126,7 +126,8 @@ compaction_proactiveness
>>
>> This tunable takes a value in the range [0, 100] with a default value of
>> 20. This tunable determines how aggressively compaction is done in the
>> -background. Setting it to 0 disables proactive compaction.
>> +background. On write of non zero value to this tunable will immediately
>> +trigger the proactive compaction. Setting it to 0 disables proactive compaction.
>>
>> Note that compaction has a non-trivial system-wide impact as pages
>> belonging to different processes are moved around, which could also lead
>> diff --git a/include/linux/compaction.h b/include/linux/compaction.h
>> index 4221888..04d5d9f 100644
>> --- a/include/linux/compaction.h
>> +++ b/include/linux/compaction.h
>> @@ -84,6 +84,8 @@ static inline unsigned long compact_gap(unsigned int order)
>> extern unsigned int sysctl_compaction_proactiveness;
>> extern int sysctl_compaction_handler(struct ctl_table *table, int write,
>> void *buffer, size_t *length, loff_t *ppos);
>> +extern int compaction_proactiveness_sysctl_handler(struct ctl_table *table,
>> + int write, void *buffer, size_t *length, loff_t *ppos);
>> extern int sysctl_extfrag_threshold;
>> extern int sysctl_compact_unevictable_allowed;
>>
>> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
>> index 0d53eba..9455809 100644
>> --- a/include/linux/mmzone.h
>> +++ b/include/linux/mmzone.h
>> @@ -815,6 +815,7 @@ typedef struct pglist_data {
>> enum zone_type kcompactd_highest_zoneidx;
>> wait_queue_head_t kcompactd_wait;
>> struct task_struct *kcompactd;
>> + bool proactive_compact_trigger;
>> #endif
>> /*
>> * This is a per-node reserve of pages that are not available
>> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
>> index 14edf84..bed2fad 100644
>> --- a/kernel/sysctl.c
>> +++ b/kernel/sysctl.c
>> @@ -2840,7 +2840,7 @@ static struct ctl_table vm_table[] = {
>> .data = &sysctl_compaction_proactiveness,
>> .maxlen = sizeof(sysctl_compaction_proactiveness),
>> .mode = 0644,
>> - .proc_handler = proc_dointvec_minmax,
>> + .proc_handler = compaction_proactiveness_sysctl_handler,
>> .extra1 = SYSCTL_ZERO,
>> .extra2 = &one_hundred,
>> },
>> diff --git a/mm/compaction.c b/mm/compaction.c
>> index 84fde27..197e203 100644
>> --- a/mm/compaction.c
>> +++ b/mm/compaction.c
>> @@ -2708,6 +2708,30 @@ static void compact_nodes(void)
>> */
>> unsigned int __read_mostly sysctl_compaction_proactiveness = 20;
>>
>> +int compaction_proactiveness_sysctl_handler(struct ctl_table *table, int write,
>> + void *buffer, size_t *length, loff_t *ppos)
>> +{
>> + int rc, nid;
>> +
>> + rc = proc_dointvec_minmax(table, write, buffer, length, ppos);
>> + if (rc)
>> + return rc;
>> +
>> + if (write && sysctl_compaction_proactiveness) {
>> + for_each_online_node(nid) {
>> + pg_data_t *pgdat = NODE_DATA(nid);
>> +
>> + if (pgdat->proactive_compact_trigger)
>> + continue;
>> +
>> + pgdat->proactive_compact_trigger = true;
>> + wake_up_interruptible(&pgdat->kcompactd_wait);
>> + }
>> + }
>> +
>> + return 0;
>> +}
>> +
>> /*
>> * This is the entry point for compacting all nodes via
>> * /proc/sys/vm/compact_memory
>> @@ -2752,7 +2776,8 @@ void compaction_unregister_node(struct node *node)
>>
>> static inline bool kcompactd_work_requested(pg_data_t *pgdat)
>> {
>> - return pgdat->kcompactd_max_order > 0 || kthread_should_stop();
>> + return pgdat->kcompactd_max_order > 0 || kthread_should_stop() ||
>> + pgdat->proactive_compact_trigger;
>> }
>>
>> static bool kcompactd_node_suitable(pg_data_t *pgdat)
>> @@ -2905,7 +2930,8 @@ static int kcompactd(void *p)
>> trace_mm_compaction_kcompactd_sleep(pgdat->node_id);
>> if (wait_event_freezable_timeout(pgdat->kcompactd_wait,
>> kcompactd_work_requested(pgdat),
>> - msecs_to_jiffies(HPAGE_FRAG_CHECK_INTERVAL_MSEC))) {
>> + msecs_to_jiffies(HPAGE_FRAG_CHECK_INTERVAL_MSEC)) &&
>> + !pgdat->proactive_compact_trigger) {
>>
>> psi_memstall_enter(&pflags);
>> kcompactd_do_work(pgdat);
>> @@ -2917,10 +2943,20 @@ static int kcompactd(void *p)
>> if (should_proactive_compact_node(pgdat)) {
>> unsigned int prev_score, score;
>>
>> - if (proactive_defer) {
>> + /*
>> + * On wakeup of proactive compaction by sysctl
>> + * write, ignore the accumulated defer score.
>> + * Anyway, if the proactive compaction didn't
>> + * make any progress for the new value, it will
>> + * be further deferred by 2^COMPACT_MAX_DEFER_SHIFT
>> + * times.
>> + */
>> + if (proactive_defer &&
>> + !pgdat->proactive_compact_trigger) {
>> proactive_defer--;
>> continue;
>> }
>> +
>> prev_score = fragmentation_score_node(pgdat);
>> proactive_compact_node(pgdat);
>> score = fragmentation_score_node(pgdat);
>> @@ -2931,6 +2967,8 @@ static int kcompactd(void *p)
>> proactive_defer = score < prev_score ?
>> 0 : 1 << COMPACT_MAX_DEFER_SHIFT;
>> }
>> + if (pgdat->proactive_compact_trigger)
>> + pgdat->proactive_compact_trigger = false;
>> }
>>
>> return 0;
>>
>
--
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