+CC linux-api On 5/18/21 3:37 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@xxxxxxxxxxxxxx> Cancelling all current sleeps immediately when the controlling variable changes doesn't sound wrong to me. A question below: > --- > changes in V2: > - remove /proc interface trigger for proactive compaction > - Intention is same that add a way to trigger proactive compaction by user. > > changes in V1: > - https://lore.kernel.org/lkml/1619098678-8501-1-git-send-email-charante@xxxxxxxxxxxxxx/ > > include/linux/compaction.h | 2 ++ > include/linux/mmzone.h | 1 + > kernel/sysctl.c | 2 +- > mm/compaction.c | 35 ++++++++++++++++++++++++++++++++--- > 4 files changed, 36 insertions(+), 4 deletions(-) > > 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..9056693 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); > @@ -2919,7 +2945,7 @@ static int kcompactd(void *p) > > if (proactive_defer) { > proactive_defer--; > - continue; > + goto loop; I don't understand this part. If we kick kcompactd from the sysctl handler because we are changing proactiveness, shouldn't we also discard any accumulated defer score? > } > prev_score = fragmentation_score_node(pgdat); > proactive_compact_node(pgdat); > @@ -2931,6 +2957,9 @@ static int kcompactd(void *p) > proactive_defer = score < prev_score ? > 0 : 1 << COMPACT_MAX_DEFER_SHIFT; > } > +loop: > + if (pgdat->proactive_compact_trigger) > + pgdat->proactive_compact_trigger = false; > } > > return 0; >
