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AJvYcCUKH7qzowQtJ/i3u/JIg0mHhpZrTv/YQAvTL5gQ0pBc1ubrkXLC4e0vu5u/NnSud1NWBQo8EgAbvQ==@kvack.org X-Gm-Message-State: AOJu0YyglqnnBECvYQFcP5QDOUSYYhloy/NQaKVpgYRtYTt6JnrO0CCa 4D47b0DAHenOgt896rEdd9hrytsQ4fmIo8A4I+NEjDiQRkSvbvPrLj4O+X0BHNh8oL8EoEtkKlW ZVcFhYsUd6qQozfTHadnMJhviH1+uX8RcEbGGAjB/07Gt+3dqBwI9 X-Google-Smtp-Source: AGHT+IEo6Q/3tFGZj8m8ATzcp9PmqvulcLtNoRpqubB5FMK6mvuYFDL5YqQ75170LA2WrLnXhPk/u+ryx/fs3sK5EZc= X-Received: by 2002:a05:6102:3ec5:b0:48f:463c:2fbd with SMTP id ada2fe7eead31-49743943122mr2196881137.2.1723502576522; Mon, 12 Aug 2024 15:42:56 -0700 (PDT) MIME-Version: 1.0 References: <20240811041703.2775153-1-yuzhao@google.com> In-Reply-To: From: Yu Zhao Date: Mon, 12 Aug 2024 16:42:19 -0600 Message-ID: Subject: Re: [PATCH mm-unstable v1] mm/hugetlb_vmemmap: batch HVO work when demoting To: Muchun Song Cc: Andrew Morton , Linux Memory Management List , linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: hybbqxquid7krnjrtghqgmebhfniztz4 X-Rspamd-Queue-Id: C0D2EA0003 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1723502577-965646 X-HE-Meta: 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 hMqc76SO r5praz3De49lTocnRPbRZ1MZb7FBoESRXUOpU+kuVdrBGBNAQZqPgjg5hgvbIWnX1Yl9NM1COQqVOA6tRx1tq4sVDFGK5TO09FuDuZucyI+l9eNrQDI7lcdXjCzV2dWM8jsdXxERiGnwrnXgbGc3L/rxJV3L2H8X/lQZp0AoPurmjXjgXUolJALBqmmebbMzfop/Caa/jZBpnGbRH+gqzEpYHyaw1dJrHXqaPU5e8KWjWEv6MerMMI0mp48DsbNJxg4jYsyN5eAUtTKhDz2ESCzOBzQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, 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 Mon, Aug 12, 2024 at 3:40=E2=80=AFAM Muchun Song = wrote: > > > > > On Aug 11, 2024, at 12:17, Yu Zhao wrote: > > > > Batch the HVO work, including de-HVO of the source and HVO of the > > destination hugeTLB folios, to speed up demotion. > > > > After commit bd225530a4c7 ("mm/hugetlb_vmemmap: fix race with > > speculative PFN walkers"), each request of HVO or de-HVO, batched or > > not, invokes synchronize_rcu() once. For example, when not batched, > > demoting one 1GB hugeTLB folio to 512 2MB hugeTLB folios invokes > > synchronize_rcu() 513 times (1 de-HVO plus 512 HVO requests), whereas > > when batched, only twice (1 de-HVO plus 1 HVO request). And > > performance between the two cases are significantly different, e.g., > > echo 2048kB >/sys/kernel/mm/hugepages/hugepages-1048576kB/demote_size > > time echo 100 >/sys/kernel/mm/hugepages/hugepages-1048576kB/demote > > > > Before this patch: > > real 8m58.158s > > user 0m0.009s > > sys 0m5.900s > > > > After this patch: > > real 0m0.900s > > user 0m0.000s > > sys 0m0.851s > > > > Fixes: bd225530a4c7 ("mm/hugetlb_vmemmap: fix race with speculative PFN= walkers") > > Signed-off-by: Yu Zhao > > Reviewed-by: Muchun Song Thanks! I forgot to mention (in the commit message) that: This patch changes the behavior of the `demote` interface when de-HVO fails. Before, the interface aborts immediately upon failure; now, it tries to finish an entire batch, meaning it can make extra progress if the rest of the batch contains folios that do not need to de-HVO. Will post v2 to fix this.