From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ua0-f200.google.com (mail-ua0-f200.google.com [209.85.217.200]) by kanga.kvack.org (Postfix) with ESMTP id AAC386B0388 for ; Tue, 14 Mar 2017 19:07:40 -0400 (EDT) Received: by mail-ua0-f200.google.com with SMTP id u81so166672uau.6 for ; Tue, 14 Mar 2017 16:07:40 -0700 (PDT) Received: from mail-ua0-x244.google.com (mail-ua0-x244.google.com. [2607:f8b0:400c:c08::244]) by mx.google.com with ESMTPS id l192si32927vka.165.2017.03.14.16.07.39 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 14 Mar 2017 16:07:39 -0700 (PDT) Received: by mail-ua0-x244.google.com with SMTP id f54so63881uaa.0 for ; Tue, 14 Mar 2017 16:07:39 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20170313095836.GI31518@dhcp22.suse.cz> References: <20170307131751.24936-1-mhocko@kernel.org> <20170313095836.GI31518@dhcp22.suse.cz> From: Yang Li Date: Tue, 14 Mar 2017 18:07:38 -0500 Message-ID: Subject: Re: [PATCH] mm: move pcp and lru-pcp drainging into single wq Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Andrew Morton , Tetsuo Handa , Vlastimil Babka , Mel Gorman , linux-mm@kvack.org, LKML , Li Yang , "linux-arm-kernel@lists.infradead.org" On Mon, Mar 13, 2017 at 4:58 AM, Michal Hocko wrote: > On Fri 10-03-17 17:31:56, Yang Li wrote: >> On Tue, Mar 7, 2017 at 7:17 AM, Michal Hocko wrote: >> > From: Michal Hocko >> > >> > 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 >> >> So what's the plan if this really happens? Shall we put the >> initialization of the mm_percpu_wq earlier? > > yes > >> Or if it is really harmless we can probably remove the warnings. > > Yeah, it is harmless but if we can move it earlier then it would be > prefferable to fix this. > >> >> I'm seeing this on arm64 with a linux-next tree: > [...] >> [ 0.279000] [] drain_all_pages+0x244/0x25c >> [ 0.279065] [] start_isolate_page_range+0x14c/0x1f0 >> [ 0.279137] [] alloc_contig_range+0xec/0x354 >> [ 0.279203] [] cma_alloc+0x100/0x1fc >> [ 0.279263] [] dma_alloc_from_contiguous+0x3c/0x44 >> [ 0.279336] [] atomic_pool_init+0x7c/0x208 >> [ 0.279399] [] arm64_dma_init+0x44/0x4c >> [ 0.279461] [] do_one_initcall+0x38/0x128 >> [ 0.279525] [] kernel_init_freeable+0x1a0/0x240 >> [ 0.279596] [] kernel_init+0x10/0xfc >> [ 0.279654] [] ret_from_fork+0x10/0x20 > > The following should address this. I didn't get to test it yet though. > --- > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 21ee5503c702..8362dca071cb 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -32,6 +32,8 @@ struct user_struct; > struct writeback_control; > struct bdi_writeback; > > +void init_mm_internals(void); > + > #ifndef CONFIG_NEED_MULTIPLE_NODES /* Don't use mapnrs, do it properly */ > extern unsigned long max_mapnr; > > diff --git a/init/main.c b/init/main.c > index 51aa8f336819..c72d35250e84 100644 > --- a/init/main.c > +++ b/init/main.c > @@ -1023,6 +1023,8 @@ static noinline void __init kernel_init_freeable(void) > > workqueue_init(); > > + init_mm_internals(); > + > do_pre_smp_initcalls(); > lockup_detector_init(); > > diff --git a/mm/vmstat.c b/mm/vmstat.c > index 4bbc775f9d08..d0871fc1aeca 100644 > --- a/mm/vmstat.c > +++ b/mm/vmstat.c > @@ -1762,7 +1762,7 @@ static int vmstat_cpu_dead(unsigned int cpu) > > struct workqueue_struct *mm_percpu_wq; > > -static int __init setup_vmstat(void) > +void __init init_mm_internals(void) > { > int ret __maybe_unused; > > @@ -1792,9 +1792,7 @@ static int __init setup_vmstat(void) > proc_create("vmstat", S_IRUGO, NULL, &proc_vmstat_file_operations); > proc_create("zoneinfo", S_IRUGO, NULL, &proc_zoneinfo_file_operations); > #endif > - return 0; > } > -module_init(setup_vmstat) > > #if defined(CONFIG_DEBUG_FS) && defined(CONFIG_COMPACTION) I did a test on arm64. This do fix the warnings. Regards, Leo -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org