Messages in this thread | | | From | Shakeel Butt <> | Date | Thu, 22 Apr 2021 11:51:53 -0700 | Subject | Re: [RFC] mm/vmscan.c: avoid possible long latency caused by too_many_isolated() |
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On Thu, Apr 22, 2021 at 10:13 AM Yu Zhao <yuzhao@google.com> wrote: > [...] > spin_lock_irq(&lruvec->lru_lock); > @@ -3302,6 +3252,7 @@ static bool throttle_direct_reclaim(gfp_t gfp_mask, struct zonelist *zonelist, > unsigned long try_to_free_pages(struct zonelist *zonelist, int order, > gfp_t gfp_mask, nodemask_t *nodemask) > { > + int nr_cpus; > unsigned long nr_reclaimed; > struct scan_control sc = { > .nr_to_reclaim = SWAP_CLUSTER_MAX, > @@ -3334,8 +3285,17 @@ unsigned long try_to_free_pages(struct zonelist *zonelist, int order, > set_task_reclaim_state(current, &sc.reclaim_state); > trace_mm_vmscan_direct_reclaim_begin(order, sc.gfp_mask); > > + nr_cpus = current_is_kswapd() ? 0 : num_online_cpus();
kswapd does not call this function (directly or indirectly).
> + while (nr_cpus && !atomic_add_unless(&pgdat->nr_reclaimers, 1, nr_cpus)) {
At most nr_nodes * nr_cpus direct reclaimers are allowed?
> + if (schedule_timeout_killable(HZ / 10))
trace_mm_vmscan_direct_reclaim_end() and set_task_reclaim_state(NULL)?
> + return SWAP_CLUSTER_MAX; > + } > + > nr_reclaimed = do_try_to_free_pages(zonelist, &sc); > > + if (nr_cpus) > + atomic_dec(&pgdat->nr_reclaimers); > + > trace_mm_vmscan_direct_reclaim_end(nr_reclaimed); > set_task_reclaim_state(current, NULL);
BTW I think this approach needs to be more sophisticated. What if a direct reclaimer within the reclaim is scheduled away and is out of CPU quota?
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