On Fri, Jul 30, 2021 at 07:23:27PM +0530, 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). So, 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> Acked-by: Rafael Aquini <aquini@xxxxxxxxxx> > --- > Changes in V5: > -- Avoid unnecessary wakeup of proactive compaction when it is disabled. > -- No changes in the logic of triggering the proactive compaction. > > Changes in V4: > -- Changed the code as the 'proactive_defer' counter is removed. > -- No changes in the logic of triggering the proactive compaction. > -- https://lore.kernel.org/patchwork/patch/1448777/ > > Changes in V3: > -- Fixed review comments from Valstimil and others. > -- https://lore.kernel.org/patchwork/patch/1438211/ > > Changes in V2: > -- remove /proc/../proactive_compact_memory interface trigger for proactive compaction > -- Intention is same that add a way to trigger proactive compaction by user. > -- https://lore.kernel.org/patchwork/patch/1431283/ > > changes in V1: > -- Created the new /proc/sys/vm/proactive_compact_memory in > interface to trigger proactive compaction from user > -- https://lore.kernel.org/lkml/1619098678-8501-1-git-send-email-charante@xxxxxxxxxxxxxx/ > > Documentation/admin-guide/sysctl/vm.rst | 3 ++- > include/linux/compaction.h | 2 ++ > include/linux/mmzone.h | 1 + > kernel/sysctl.c | 2 +- > mm/compaction.c | 38 +++++++++++++++++++++++++++++++-- > 5 files changed, 42 insertions(+), 4 deletions(-) > > diff --git a/Documentation/admin-guide/sysctl/vm.rst b/Documentation/admin-guide/sysctl/vm.rst > index 003d5cc..b526cf6 100644 > --- a/Documentation/admin-guide/sysctl/vm.rst > +++ b/Documentation/admin-guide/sysctl/vm.rst > @@ -118,7 +118,8 @@ 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 c24098c..34bce35 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 4610750..6a1d79d 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -853,6 +853,7 @@ 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 82d6ff6..65bc6f7 100644 > --- a/kernel/sysctl.c > +++ b/kernel/sysctl.c > @@ -2871,7 +2871,7 @@ 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 f984ad0..fbc60f9 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -2700,6 +2700,30 @@ 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 > @@ -2744,7 +2768,8 @@ 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) > @@ -2895,9 +2920,16 @@ static int kcompactd(void *p) > while (!kthread_should_stop()) { > unsigned long pflags; > > + /* > + * Avoid the unnecessary wakeup for proactive compaction > + * when it is disabled. > + */ > + if (!sysctl_compaction_proactiveness) > + timeout = MAX_SCHEDULE_TIMEOUT; > trace_mm_compaction_kcompactd_sleep(pgdat->node_id); > if (wait_event_freezable_timeout(pgdat->kcompactd_wait, > - kcompactd_work_requested(pgdat), timeout)) { > + kcompactd_work_requested(pgdat), timeout) && > + !pgdat->proactive_compact_trigger) { > > psi_memstall_enter(&pflags); > kcompactd_do_work(pgdat); > @@ -2932,6 +2964,8 @@ static int kcompactd(void *p) > timeout = > default_timeout << COMPACT_MAX_DEFER_SHIFT; > } > + if (unlikely(pgdat->proactive_compact_trigger)) > + pgdat->proactive_compact_trigger = false; > } > > return 0; > -- > QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a > member of the Code Aurora Forum, hosted by The Linux Foundation > >
