On 7/30/21 3:53 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). 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: Vlastimil Babka <vbabka@xxxxxxx> > @@ -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; Does this part actually logically belong more to your previous patch that optimized the deferred timeouts? > 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; >
