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Tsirkin" , Michal Hocko , Muchun Song , "Aneesh Kumar K.V" , Tejun Heo References: <563d1eef-b780-835a-ebf0-88ae111b20c2@redhat.com> <65a1946f-dbf9-5767-5b51-9c1b786051d1@redhat.com> <5f196069-8b98-0ad3-55e8-19af03d715cd@oracle.com> <312246f4-4e5f-1425-1bc2-1b356db0fbad@oracle.com> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: <0012e70b-3b48-df81-1dbd-29bd37e5b7e8@redhat.com> Date: Wed, 21 Oct 2020 14:42:04 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.3.1 MIME-Version: 1.0 In-Reply-To: <312246f4-4e5f-1425-1bc2-1b356db0fbad@oracle.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 21.10.20 05:35, Mike Kravetz wrote: > On 10/20/20 6:38 AM, David Hildenbrand wrote: >> >> I'm bisecting the warning right now. Looks like it was introduced in v5.7. > So bisecting nailed it down to one of 353b2de42e84 mm/hugetlb.c: clean code by removing unnecessary initialization a9b3f867404b hugetlb: support file_region coalescing again 08cf9faf7558 hugetlb_cgroup: support noreserve mappings 075a61d07a8e hugetlb_cgroup: add accounting for shared mappings 0db9d74ed884 hugetlb: disable region_add file_region coalescing e9fe92ae0cd2 hugetlb_cgroup: add reservation accounting for private mappings 9808895e1a44 mm/hugetlb_cgroup: fix hugetlb_cgroup migration 1adc4d419aa2 hugetlb_cgroup: add interface for charge/uncharge hugetlb reservations cdc2fcfea79b hugetlb_cgroup: add hugetlb_cgroup reservation counter So seems to be broken right from the beginning of charge/uncharge/reservations. Not a surpise when looking at your fixes :) > I found the following bugs in the cgroup reservation accounting. The ones > in region_del are pretty obvious as the number of pages to uncharge would > always be zero. The one on alloc_huge_page needs racing code to expose. > > With these fixes, my testing is showing consistent/correct results for > hugetlb reservation cgroup accounting. > > It would be good if Mina (at least) would look these over. Would also > be interesting to know if these fixes address the bug seen with the qemu > use case. I strongly suspect it will. Compiling, will reply in half an our or so with the result. > > I'm still doing more testing and code inspection to look for other issues. When sending, can you make sure to credit Michal P.? Thanks! Reported-by: Michal Privoznik > > From 861bcd7d0443f18a5fed3c3ddc5f1c71e78c4ef4 Mon Sep 17 00:00:00 2001 > From: Mike Kravetz > Date: Tue, 20 Oct 2020 20:21:42 -0700 > Subject: [PATCH] hugetlb_cgroup: fix reservation accounting > > Signed-off-by: Mike Kravetz > --- > mm/hugetlb.c | 15 +++++++++------ > 1 file changed, 9 insertions(+), 6 deletions(-) > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index 67fc6383995b..c92366313780 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -685,17 +685,17 @@ static long region_del(struct resv_map *resv, long f, long t) > } > > if (f <= rg->from) { /* Trim beginning of region */ > - del += t - rg->from; > - rg->from = t; > - > hugetlb_cgroup_uncharge_file_region(resv, rg, > t - rg->from); > - } else { /* Trim end of region */ > - del += rg->to - f; > - rg->to = f; > > + del += t - rg->from; > + rg->from = t; > + } else { /* Trim end of region */ > hugetlb_cgroup_uncharge_file_region(resv, rg, > rg->to - f); > + > + del += rg->to - f; > + rg->to = f; Those two look very correct to me. You could keep computing "del" before the uncharge, similar to the /* Remove entire region */ case. > } > } > > @@ -2454,6 +2454,9 @@ struct page *alloc_huge_page(struct vm_area_struct *vma, > > rsv_adjust = hugepage_subpool_put_pages(spool, 1); > hugetlb_acct_memory(h, -rsv_adjust); > + if (deferred_reserve) > + hugetlb_cgroup_uncharge_page_rsvd(hstate_index(h), > + That looks correct to me as well. > } > return page; > > Thanks for debugging! -- Thanks, David / dhildenb