Messages in this thread Patch in this message | | | Subject | Re: [Resend PATCH 2/6] mm/memcg: remove useless check on page->mem_cgroup | From | Alex Shi <> | Date | Wed, 12 Aug 2020 11:25:53 +0800 |
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在 2020/8/11 下午9:56, Michal Hocko 写道: > On Tue 11-08-20 20:54:18, Alex Shi wrote: >> >From beeac61119ab39b1869c520c0f272fb8bab93765 Mon Sep 17 00:00:00 2001 >> From: Alex Shi <alex.shi@linux.alibaba.com> >> Date: Wed, 5 Aug 2020 21:02:30 +0800 >> Subject: [PATCH 2/6] memcg: bail out early from swap accounting when memcg is >> disabled>> >> If we disabled memcg by cgroup_disable=memory, the swap charges are >> still called. Let's return from the funcs earlier. > They are not, are they? page->memcg will be NULL and so the charge is > skipped and that will trigger a warning with your current ordering.
Hi Michal,
Thanks for comment! Looks like we both agree the memcg wasn't charged, but funcs just are called. :)
> > Let me repeat again. Either you put it first in the series and argue > that we can bail out early or keep the ordering then this makes sure the > warning doesn't trigger. >
Is the following commit log fine?
Thanks! Alex
From 999b0fe5fc65865c3b59ff28500d45572a4a9570 Mon Sep 17 00:00:00 2001 From: Alex Shi <alex.shi@linux.alibaba.com> Date: Wed, 5 Aug 2020 21:02:30 +0800 Subject: [PATCH 2/6] mm/memcg: bail out early from swap accounting when memcg is disabled
If we disabled memcg by cgroup_disable=memory, page->memcg will be NULL and so the charge is skipped and that will trigger a warning like below. Let's return from the funcs earlier.
---[ end trace f1f34bfc3b32ed2f ]--- anon flags:0x5005b48008000d(locked|uptodate|dirty|swapbacked) raw: 005005b48008000d dead000000000100 dead000000000122 ffff8897c7c76ad1 raw: 0000000000000022 0000000000000000 0000000200000000 0000000000000000 page dumped because: VM_WARN_ON_ONCE_PAGE(!memcg)
Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com> Reviewed-by: Roman Gushchin <guro@fb.com> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: cgroups@vger.kernel.org Cc: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org --- mm/memcontrol.c | 6 ++++++ 1 file changed, 6 insertions(+)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 299382fc55a9..419cf565f40b 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -7098,6 +7098,9 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry) VM_BUG_ON_PAGE(PageLRU(page), page); VM_BUG_ON_PAGE(page_count(page), page); + if (mem_cgroup_disabled()) + return; + if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) return; @@ -7163,6 +7166,9 @@ int mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry) struct mem_cgroup *memcg; unsigned short oldid; + if (mem_cgroup_disabled()) + return 0; + if (!cgroup_subsys_on_dfl(memory_cgrp_subsys)) return 0; -- 1.8.3.1
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