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Fri, 15 Dec 2023 00:33:57 -0800 (PST) MIME-Version: 1.0 References: <20231215074619.173787-1-aravinda.prasad@intel.com> In-Reply-To: <20231215074619.173787-1-aravinda.prasad@intel.com> From: Yu Zhao Date: Fri, 15 Dec 2023 01:33:18 -0700 Message-ID: Subject: Re: mm/DAMON: Profiling enhancements for DAMON To: Aravinda Prasad Cc: damon@lists.linux.dev, linux-mm@kvack.org, sj@kernel.org, linux-kernel@vger.kernel.org, s2322819@ed.ac.uk, sandeep4.kumar@intel.com, ying.huang@intel.com, dave.hansen@intel.com, dan.j.williams@intel.com, sreenivas.subramoney@intel.com, antti.kervinen@intel.com, alexander.kanevskiy@intel.com, Alan Nair , Juergen Gross , Ryan Roberts Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: CD2FA180016 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: rcxb595s6s19trzfmjukfks113x44eou X-HE-Tag: 1702629238-481618 X-HE-Meta: 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 zk757y/x THY6+hwoQuGNQ3lIFxtnqkUTsyKdigjKUOhS8RqF/uGZR0XO/q09d6Z6qRJ9CKhwUll99kM299ZfJO0qddQUlTq83R3SVfljvCMGVpYQAPo+ocJKJVauMCeAtzZ0K/GMBQyzIIgZH7bRDgsXZsmKTWZxl1ECpzWxKgKKoT+DWGZJM6DrU985pmnay73fMp78w+sTwIym5fmg/OBNPLOIZeMUdWiKpfOL10bKfw8b/7AC9q8nM00sckLvVYQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.201106, 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 Fri, Dec 15, 2023 at 12:42=E2=80=AFAM Aravinda Prasad wrote: ... > This patch proposes profiling different levels of the application=E2=80= =99s > page table tree to detect whether a region is accessed or not. This > patch is based on the observation that, when the accessed bit for a > page is set, the accessed bits at the higher levels of the page table > tree (PMD/PUD/PGD) corresponding to the path of the page table walk > are also set. Hence, it is efficient to check the accessed bits at > the higher levels of the page table tree to detect whether a region > is accessed or not. This patch can crash on Xen. See commit 4aaf269c768d("mm: introduce arch_has_hw_nonleaf_pmd_young()") MGLRU already does this in the correct way. See mm/vmscan.c. This patch also can cause USER DATA CORRUPTION. See commit c11d34fa139e ("mm/damon/ops-common: atomically test and clear young on ptes and pmds"). The quality of your patch makes me very much doubt the quality of your paper, especially your results on Google's kstaled and MGLRU in table 6.2.