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[71.184.117.43]) by smtp.gmail.com with ESMTPSA id b4sm13161136qtp.63.2020.06.21.16.53.24 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 21 Jun 2020 16:53:24 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable From: Qian Cai Mime-Version: 1.0 (1.0) Subject: Re: [PATCH v6 00/19] The new cgroup slab memory controller Date: Sun, 21 Jun 2020 19:53:23 -0400 Message-Id: <7DEA68BC-3B9A-46FA-8103-AE6B72324591@lca.pw> References: <20200621233429.GA293939@carbon.DHCP.thefacebook.com> Cc: Andrew Morton , Christoph Lameter , Johannes Weiner , Michal Hocko , Shakeel Butt , linux-mm@kvack.org, Vlastimil Babka , kernel-team@fb.com, linux-kernel@vger.kernel.org, catalin.marinas@arm.com In-Reply-To: <20200621233429.GA293939@carbon.DHCP.thefacebook.com> To: Roman Gushchin X-Mailer: iPhone Mail (17F80) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Jun 21, 2020, at 7:34 PM, Roman Gushchin wrote: >=20 > My wild guess is that kmemleak is getting confused by modifying the lowest= > bit of page->mem_cgroup/obhj_cgroups pointer: >=20 > struct page { > ... > union { > struct mem_cgroup *mem_cgroup; > struct obj_cgroup **obj_cgroups; > }; > ... > } >=20 > We're using the lowest bit to distinguish between a "normal" mem_cgroup > pointer and a vector of obj_cgroup pointers. >=20 > This pointer to obj_cgroup vector is saved only here, so if we're modifyin= g > the address, I guess it's what makes kmemleak think that there is a leak. >=20 > Or do you have a real leak? The point is that we can=E2=80=99t have a patchset in the current form to to= tally render kmemleak useless with so many even false positives. Anyway, this is rather easy to reproduce where I am able to reproduce on mul= tiple bare-metal machines by just booting it. # echo scan > /sys/kernel/debug/kmemleak # cat /sys/kernel/debug/kmemleak=