Thanks Vlastimil for your inputs!! On 6/16/2021 5:29 PM, Vlastimil Babka wrote: >> 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> >> --- >> changes in V2: > You forgot to also summarize the changes. Please do in next version. Sure. Will take care this in the next version. > >> */ >> 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; > I don't like the new variable. I wish we could do without it. I understand this > is added to ignore proactive_defer. > We could instead expose proactive_defer in pgdat and reset it to 0 before wakeup > (instead being a thread variable in kcompactd). But that would be racy with the > decreases done by kcompactd. > But I like the patch 2/2 and the idea could be extended to proactive_defer > handling. If there's no proactive_defer, timeout is > HPAGE_FRAG_CHECK_INTERVAL_MSEC. If kcompactd decides to defer, timeout would be > HPAGE_FRAG_CHECK_INTERVAL_MSEC << COMPACT_MAX_DEFER_SHIFT. Thus, no more waking > up just to decrease proactive_defer, we can then get rid of the counter. On > writing new proactiveness just wake up and that's it, regardless of which > timeout there was at the moment. I think we can get rid off 'proactive_defer' thread variable with the timeout approach you suggested. But it is still requires to have one additional variable 'proactive_compact_trigger', which main purpose is to decide if the kcompactd wakeup is for proactive compaction or not. Please see below code: if (wait_event_freezable_timeout() && !proactive_compact_trigger) { // do the non-proactive work continue } // do the proactive work ................. Thus I feel that on writing new proactiveness, it is required to do wakeup_kcomppactd() + set a flag that this wakeup is for proactive work. Am I failed to get your point here? > The only change is, if we get woken up to do non-proactive work, by > wakeup_kcompactd(), the proactive_defer value would be now be effectively lost. > I think it's OK as wakeup_kcompactd() means the condition of the zone changed > substantionally anyway and carrying on with previous defer makes not much sense. > What do you think? Agree. > >> + 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; -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project
