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Tue, 30 Jan 2024 16:37:31 -0800 (PST) MIME-Version: 1.0 References: <20240129054551.57728-1-ioworker0@gmail.com> In-Reply-To: From: Lance Yang Date: Wed, 31 Jan 2024 08:37:20 +0800 Message-ID: Subject: Re: [PATCH 1/1] mm/khugepaged: bypassing unnecessary scans with MMF_DISABLE_THP check To: Michal Hocko , "Zach O'Keefe" , Yang Shi Cc: akpm@linux-foundation.org, david@redhat.com, songmuchun@bytedance.com, peterx@redhat.com, minchan@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 16C9DA0014 X-Stat-Signature: kw4na1eo57i7zwzxocfqp458y4cuakqm X-Rspam-User: X-HE-Tag: 1706661451-949607 X-HE-Meta: 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 tDYnBRkV IJXuAJ5kOL/uB38Y2zkoPHe5lRYaizOfT7TQkgGJ9k/PfOoqbRiuGpS6qI3u8nq/lKOewEifx6j/ZT6pH+fWuYrZnBvDTD53DoLHlXePv6nciaoxLnv1BYbPMFwZQE2YC0IGzHlN7y4QZ3URBR6d2rHjmIrQWAvAmzwtVDPH2plu+bJpQmqHLSuEtCO1NX8OTySfyyNARO6nP4Dru/CiijKl3VtUalpyIYrj4eXeVutEh0NGtCu9OKjLORnCsakgkogjG7OKhCXCNmFU/cxiY5OrpdHN62F6fGerPv2QPHjuBv+KgvVCcrTStazvKqHYAkgNBIXSOoPoiPr5ghkjP5JGv4o+qOdTb6Q42Ttq22JqL0YgE8QV/eEAz1UPHzyhHxJP1CYDrb8YMU60bnG5JngOLnXAJXX41cwCXCXoVODhjc4kvNDmmovmkqPBSvwiXcc2nS2DZAr8od68F1AYPrA1CdaQKbkVlRHFkKnrii2kaiUc= X-Bogosity: Ham, tests=bogofilter, spamicity=0.028913, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hey Zach and Yang, Could I start a new version? Thanks, Lance On Tue, Jan 30, 2024 at 5:46=E2=80=AFPM Lance Yang wr= ote: > > On Tue, Jan 30, 2024 at 5:35=E2=80=AFPM Michal Hocko wr= ote: > > > > On Tue 30-01-24 11:08:10, Lance Yang wrote: > > > On Tue, Jan 30, 2024 at 10:12=E2=80=AFAM Lance Yang wrote: > > > > > > > > Hey Michal, > > > > > > > > Thanks for taking time to review! > > > > > > > > On some servers within our company, we deploy a > > > > daemon responsible for monitoring and updating > > > > local applications. Some applications prefer not to > > > > use THP, so the daemon calls prctl to disable THP > > > > before fork/exec. Conversely, for other applications, > > > > the daemon calls prctl to enable THP before fork/exec. > > > > > > > > Ideally, the daemon should invoke prctl after the fork, > > > > but its current implementation follows the described > > > > approach. > > > > > > In the Go standard library, there is no direct encapsulation > > > of the fork system call. Instead, fork and execve are > > > combined into one through syscall.ForkExec. > > > > OK, this is an important detail. Something that should be a part > > of the chnagelog. It is also important to note that this is not > > a correctness issue but rather an optimization to save expensive > > checks on each VMA when userspace cannot prctl itself before spawning > > into the new process. > > Thanks for pointing that out! > > I'll include it in the changelog. Good to know it's an optimization > rather than a correctness issue. > > Thanks, > Lance > > > -- > > Michal Hocko > > SUSE Labs