Thanks Vlastimil!! On 7/30/2021 7:36 PM, Vlastimil Babka 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> Thanks for the tag here. > >> @@ -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? IMO, it won't fit there. Reason is that when user writes sysctl_compaction_proactiveness = 0, it will goes to sleep with MAX_SCHEDULE_TIMEOUT. Say now user writes non-zero value to sysctl_compaction_proactiveness then no condition is there to wake it up for proactive compaction, means, it will still be in sleep with MAX_SCHEDULE_TIMEOUT. Thus this logic is put in this patch, where, proactive compaction work will be scheduled immediately on switch of proactiveness value from zero to a non-zero. > -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project
