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AJvYcCVS8zV021JIfF26yFb46lJVpX122rvU3ECNLs16QG64vRTK28YBBpr3N4IHfxEOTCro7aQ5ibWWOSkSDaac0G4GHhU= X-Gm-Message-State: AOJu0YwhfOiLEOil2UT51aMTkR8H0QIdW+nlLEQLqEAXjbOC+14odFgF HNZUEv7E8LO/LqNf7crUhYNorKCSO7fnmrP/nzX5fuwdjQ5XBJk7AGlpvtLy7lxYYosaSX7Xdxr kd7FEf3OLC3gt9cR+HfSHpTA6V60= X-Google-Smtp-Source: AGHT+IGZiyqVnGzeLuwRRcGJ0RsP/nv30kjzkOKbWuJEbCEc2gzNhlwSqQreoayCLtVYURajcgaVCsgUGjjhMnTdOp4= X-Received: by 2002:a81:9945:0:b0:607:d9fb:5144 with SMTP id q66-20020a819945000000b00607d9fb5144mr18703425ywg.13.1708593131796; Thu, 22 Feb 2024 01:12:11 -0800 (PST) MIME-Version: 1.0 References: <20240129054551.57728-1-ioworker0@gmail.com> <84fc211a-075d-44c7-a4c3-698931b6dc7c@redhat.com> In-Reply-To: <84fc211a-075d-44c7-a4c3-698931b6dc7c@redhat.com> From: Lance Yang Date: Thu, 22 Feb 2024 17:12:00 +0800 Message-ID: Subject: Re: [PATCH 1/1] mm/khugepaged: bypassing unnecessary scans with MMF_DISABLE_THP check To: David Hildenbrand Cc: akpm@linux-foundation.org, mhocko@suse.com, zokeefe@google.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-Rspamd-Queue-Id: 61741C0002 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: 3e7sbw7ykujrto81aq543h89hh4wzte7 X-HE-Tag: 1708593134-206603 X-HE-Meta: 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 b5B7pSpA Wr3btZpfTjfUxl/rN+5ypfGl6NsbwYnrOiP30UOsCslzuDCDMx4HKE8ORvvGgpwEkTX5oDcm+yWFA+1mu+XMAw7B74HwMCrlyjdXCdQUFOXTvdjnrLku6n3tiIE2w9Ry1rUHXHXJq++eZfDyLHRlW/J0W5T7GYpFub4qAkw3bfU8F4fV9vK6gb6RyOJmuEjwVRkl+TEkmacuHKkcKZQIIAZ0bQxFr69huItBDlFbcndmbnNUEIOiXvYFaX4mWtODd5KMgYO4JsfTjJVslZLCzxMejPR3qF6/iQvyEVXTKEJQe6phYLZAuyl0gqi19LlMjJD7M/s7HtR+w8ZsvbSkPAFmnAtcglVZZ8IWN2Egz9Ye/xAI5l2JpgNs6KESeFlNeI91TKG+WJsI1C9Ib+j1rIW8UWQ/IOVVkEM5nk0CTbIr65Pc= X-Bogosity: Ham, tests=bogofilter, spamicity=0.135709, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Thanks, David! On Thu, Feb 22, 2024 at 4:51=E2=80=AFPM David Hildenbrand wrote: > > On 22.02.24 08:51, Lance Yang wrote: > > Hey, > > > > On an Intel Core i5 CPU, the time taken by > > khugepaged to scan the address space of > > the process, which has been set with the > > MMF_DISABLE_THP flag after being added > > to the mm_slots list, is as follows (shorter is better): > > > > VMA Count | Old | New | Change > > --------------------------------------- > > 50 | 23us | 9us | -60.9% > > 100 | 32us | 9us | -71.9% > > 200 | 44us | 9us | -79.5% > > 400 | 75us | 9us | -88.0% > > 800 | 98us | 9us | -90.8% > > > > IIUC, once the count of VMAs for the process > > exceeds page_to_scan, khugepaged needs to > > wait for scan_sleep_millisecs ms before scanning > > the next process. IMO, unnecessary scans could > > actually be skipped with a very inexpensive > > mm->flags check in this case. > > FWIW > > Acked-by: David Hildenbrand > > -- > Cheers, > > David / dhildenb >