On Tue, Mar 07, 2017 at 02:17:51PM +0100, Michal Hocko wrote: > From: Michal Hocko <[email protected]> > > We currently have 2 specific WQ_RECLAIM workqueues in the mm code. > vmstat_wq for updating pcp stats and lru_add_drain_wq dedicated to drain > per cpu lru caches. This seems more than necessary because both can run > on a single WQ. Both do not block on locks requiring a memory allocation > nor perform any allocations themselves. We will save one rescuer thread > this way. > > On the other hand drain_all_pages() queues work on the system wq which > doesn't have rescuer and so this depend on memory allocation (when all > workers are stuck allocating and new ones cannot be created). This is > not critical as there should be somebody invoking the OOM killer (e.g. > the forking worker) and get the situation unstuck and eventually > performs the draining. Quite annoying though. This worker should be > using WQ_RECLAIM as well. We can reuse the same one as for lru draining > and vmstat. > > Changes since v1 > - rename vmstat_wq to mm_percpu_wq - per Mel > - make sure we are not trying to enqueue anything while the WQ hasn't > been intialized yet. This shouldn't happen because the initialization > is done from an init code but some init section might be triggering > those paths indirectly so just warn and skip the draining in that case > per Vlastimil > - do not propagate error from setup_vmstat to keep the previous behavior > per Mel > > Suggested-by: Tetsuo Handa <[email protected]> > Signed-off-by: Michal Hocko <[email protected]>
Acked-by: Mel Gorman <[email protected]> > +struct workqueue_struct *mm_percpu_wq; > + > static int __init setup_vmstat(void) > { > -#ifdef CONFIG_SMP > - int ret; > + int ret __maybe_unused; > > + mm_percpu_wq = alloc_workqueue("vmstat", WQ_FREEZABLE|WQ_MEM_RECLAIM, > 0); > + > +#ifdef CONFIG_SMP > ret = cpuhp_setup_state_nocalls(CPUHP_MM_VMSTAT_DEAD, "mm/vmstat:dead", > NULL, vmstat_cpu_dead); > if (ret < 0) Should the workqueue also have been renamed to mm_percpu_wq? -- Mel Gorman SUSE Labs
