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Tue, 28 Nov 2023 16:31:03 -0800 (PST) MIME-Version: 1.0 References: <20231128204938.1453583-1-pasha.tatashin@soleen.com> <20231128235214.GD1312390@ziepe.ca> <20231129002826.GG1312390@ziepe.ca> In-Reply-To: <20231129002826.GG1312390@ziepe.ca> From: Yosry Ahmed Date: Tue, 28 Nov 2023 16:30:27 -0800 Message-ID: Subject: Re: [PATCH 00/16] IOMMU memory observability To: Jason Gunthorpe Cc: Pasha Tatashin , akpm@linux-foundation.org, alex.williamson@redhat.com, alim.akhtar@samsung.com, alyssa@rosenzweig.io, asahi@lists.linux.dev, baolu.lu@linux.intel.com, bhelgaas@google.com, cgroups@vger.kernel.org, corbet@lwn.net, david@redhat.com, dwmw2@infradead.org, hannes@cmpxchg.org, heiko@sntech.de, iommu@lists.linux.dev, jasowang@redhat.com, jernej.skrabec@gmail.com, jonathanh@nvidia.com, joro@8bytes.org, kevin.tian@intel.com, krzysztof.kozlowski@linaro.org, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-rockchip@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-sunxi@lists.linux.dev, linux-tegra@vger.kernel.org, lizefan.x@bytedance.com, marcan@marcan.st, mhiramat@kernel.org, mst@redhat.com, m.szyprowski@samsung.com, netdev@vger.kernel.org, paulmck@kernel.org, rdunlap@infradead.org, robin.murphy@arm.com, samuel@sholland.org, suravee.suthikulpanit@amd.com, sven@svenpeter.dev, thierry.reding@gmail.com, tj@kernel.org, tomas.mudrunka@gmail.com, vdumpa@nvidia.com, virtualization@lists.linux.dev, wens@csie.org, will@kernel.org, yu-cheng.yu@intel.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: F082D120015 X-Rspam-User: X-Stat-Signature: fhmyc75xjipi17fog77qfs1shht7ras7 X-Rspamd-Server: rspam03 X-HE-Tag: 1701217864-937195 X-HE-Meta: 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 BxfnSPwe rsWLHGvYIeN+EQm2zCBeveOqZfvxGN8NzGh7tj19mm8iL4J8CC4s/vbvAFgR2gsVlIZkXcFifmI9pvntVnidzzo/MCzSeTA+T3CSjjkZiCWVPvdy5onqkjOnO9nInR+fVa3nH0hzbT9MuRmpMwu/nh+X2576KKgTontoIAhhxQhoKG1Ygjw73FZWmaEVwXgjq7raGt6cgLoEGsetpYBjd6S2jlX91IY85xeBx0H60aGAKYANZRuo4e0qK7KvU7w/HHtHUeuRunGZttz/vwB1Tu/47bKShfehk7oTByBd0cTnzss4hof3VfNX3n8ARjo3fMYuFbIIm37nMonXM9GpwLRRyORiFFzpmdaiu X-Bogosity: Ham, tests=bogofilter, spamicity=0.000002, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Nov 28, 2023 at 4:28=E2=80=AFPM Jason Gunthorpe wrot= e: > > On Tue, Nov 28, 2023 at 04:25:03PM -0800, Yosry Ahmed wrote: > > > > > Right, but as I mention above, if userspace starts depending on thi= s > > > > equation, we won't be able to add any more classes of "secondary" p= age > > > > tables to SecPageTables. I'd like to avoid that if possible. We can= do > > > > the subtraction in the kernel. > > > > > > What Sean had suggested was that SecPageTables was always intended to > > > account all the non-primary mmu memory used by page tables. If this i= s > > > the case we shouldn't be trying to break it apart into finer > > > counters. These are big picture counters, not detailed allocation by > > > owner counters. > > > > Right, I agree with that, but if SecPageTables includes page tables > > from multiple sources, and it is observed to be suspiciously high, the > > logical next step is to try to find the culprit, right? > > You can make that case already, if it is high wouldn't you want to > find the exact VMM process that was making it high? > > It is a sign of fire, not a detailed debug tool. Fair enough. We can always add separate counters later if needed, potentially under KVM stats to get more fine-grained details as you mentioned. I am only worried about users subtracting the iommu-only counter to get a KVM counter. We should at least document that SecPageTables may be expanded to include other sources later to avoid that. > > Jason