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Tue, 30 Jan 2024 01:46:28 -0800 (PST) MIME-Version: 1.0 References: <20240129054551.57728-1-ioworker0@gmail.com> In-Reply-To: From: Lance Yang Date: Tue, 30 Jan 2024 17:46:17 +0800 Message-ID: Subject: Re: [PATCH 1/1] mm/khugepaged: bypassing unnecessary scans with MMF_DISABLE_THP check To: Michal Hocko Cc: akpm@linux-foundation.org, zokeefe@google.com, david@redhat.com, songmuchun@bytedance.com, shy828301@gmail.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-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 7AD9380006 X-Stat-Signature: kiojfcs7h3htwsg3ru6sx3x1rijkprw1 X-HE-Tag: 1706607989-635231 X-HE-Meta: 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 BnHLzpJZ biEDhGB7FRZmDcempwBjtUGdJY+YXFSddElXDhmW50ihN/PNzuDudtrN87J3E9nJFvejuEBPoThOkN/SNIRw9r3oUwPUHB75WAeAwJzI/q3U/gJEg1JgM40DekU1YY0+7ps+7IPeJMP447oR1Xa1Egp2NsU+eQMsGMdIT+BmzE1poF7o6GeRn6A8VulcY3XSXDynpmMkx9Dx6Zs8eu2gXxgoBaRrJJD//spvQ8rJXEcuSDRAYC5KJlcHc4QextXy7DXX/TlkGLtwBSw5LGBwS/SYZ091AocsSNaam4VszLgFBm/vXwltKPQFjUEwBXGuJQ+lJ0/vi+1FuoYkm3vGkjb+BApWrEPd3IEpZZufOdwVVrZ1C7+/WARmXeFvh6aoNvcS+ECUB9L2xD05esZ+kHH8JhtjWz+TBFhH09nWhA03N6rx6yI7Nn+ay5QgBxq/qMCXKweLzybxPidoyCSo9ZbcZJlEtUxY10ZvCPUg2a1ykZcM= X-Bogosity: Ham, tests=bogofilter, spamicity=0.022818, 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, Jan 30, 2024 at 5:35=E2=80=AFPM Michal Hocko wrot= e: > > 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