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AJvYcCVYaRETn0ntFK0X83S4T3JrzyCzWm7lJrUfG0yNUwQE99/azFKrdjj7CS61ECnEQd6zFHubIv9K53Z7GUXJPON5b44= X-Gm-Message-State: AOJu0Yx4sfayp4j4wuJpd4qkSoSFLzIbdrnIY2z/pSl5Sdj9OUl3cgc3 m5ZK9XAqqYaAuhnh07ilEoVEQ1IqDklQouNh8ucf6Zs/Yayu2ouxCQD8MFoUui8aiDqUdXUw1B3 JpOnQRLczdEMrudopG4fC7P5Vfd4= X-Google-Smtp-Source: AGHT+IHIYR2VNeV0CMUYrwAssvNkO0tVtLB8DEASlbj+pqDLr1t588ZSLuDD8V4HNCwTzJuXO/biUv1YPhBj0gUyLO8= X-Received: by 2002:a05:6102:512c:b0:493:2177:9811 with SMTP id ada2fe7eead31-4945be08629mr15836873137.14.1722895786397; Mon, 05 Aug 2024 15:09:46 -0700 (PDT) MIME-Version: 1.0 References: <20240805160754.1081-1-justinjiang@vivo.com> In-Reply-To: <20240805160754.1081-1-justinjiang@vivo.com> From: Barry Song <21cnbao@gmail.com> Date: Tue, 6 Aug 2024 10:09:35 +1200 Message-ID: Subject: Re: [PATCH] mm: swap: mTHP frees entries as a whole To: Zhiguo Jiang Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Chris Li , opensource.kernel@vivo.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 8E01B40003 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: ucypzu8p3944ofy8fmwwhr7uc5pbg5x9 X-HE-Tag: 1722895787-480557 X-HE-Meta: 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 WC2kAhSV 1u9ZxX0XjZndJ8129nbZoxnVwMPazpmi3G2K6MoOzUdMcUnAvXn8gtEcuhOgNZJQrmH5ZrL2mQ8FxQU1on4wBFXOdTK4m4BKhX5R3SKp5NuzJg1mw9SxyKZ/z4D4ydqBy3eTC9Z8G/DyT5WM0PZgdTyqPocGAWNJmsEg1cDcrKLD9C2nOc1oyRuXdSd9c+79S4P5p5gnNi25anCBy65hFPw3m+kr1745h92INL+W1ghb372khkqZG81HGatlREyNURapW+Hf/JNE+OAWjcUUvVk0gyX2Om1/Y4DCxF3k9m9FsNJPI2X9GeFGbn0gAZxqpotJHn9Xgqgh8f6IBqWPxYcDdoPAx0qgM5V5U/UcIozjhSeVO8c7jXXjlw44kfAMvKA5uHGp42mWKY/vERzMXptICi5aPGB1N5DJZSxv7aYpFyDykz5A2r078Gg== 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 Tue, Aug 6, 2024 at 4:08=E2=80=AFAM Zhiguo Jiang = wrote: > > Support mTHP's attempt to free swap entries as a whole, which can avoid > frequent swap_info locking for every individual entry in > swapcache_free_entries(). When the swap_map count values corresponding > to all contiguous entries are all zero excluding SWAP_HAS_CACHE, the > entries will be freed directly by skippping percpu swp_slots caches. > No, this isn't quite good. Please review the work done by Chris and Kairui[= 1]; they have handled it better. On a different note, I have a patch that can handle zap_pte_range() for swap entries in batches[2][3]. [1] https://lore.kernel.org/linux-mm/20240730-swap-allocator-v5-5-cb9c148b9= 297@kernel.org/ [2] https://lore.kernel.org/linux-mm/20240803091118.84274-1-21cnbao@gmail.c= om/ [3] https://lore.kernel.org/linux-mm/CAGsJ_4wPnQqKOHx6iQcwO8bQzoBXKr2qY2AgS= xMwTQCj3-8YWw@mail.gmail.com/ > Signed-off-by: Zhiguo Jiang > --- > mm/swapfile.c | 61 +++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 61 insertions(+) > > diff --git a/mm/swapfile.c b/mm/swapfile.c > index ea023fc25d08..829fb4cfb6ec > --- a/mm/swapfile.c > +++ b/mm/swapfile.c > @@ -1493,6 +1493,58 @@ static void swap_entry_range_free(struct swap_info= _struct *p, swp_entry_t entry, > swap_range_free(p, offset, nr_pages); > } > > +/* > + * Free the contiguous swap entries as a whole, caller have to > + * ensure all entries belong to the same folio. > + */ > +static void swap_entry_range_check_and_free(struct swap_info_struct *p, > + swp_entry_t entry, int nr, bool *any_on= ly_cache) > +{ > + const unsigned long start_offset =3D swp_offset(entry); > + const unsigned long end_offset =3D start_offset + nr; > + unsigned long offset; > + DECLARE_BITMAP(to_free, SWAPFILE_CLUSTER) =3D { 0 }; > + struct swap_cluster_info *ci; > + int i =3D 0, nr_setbits =3D 0; > + unsigned char count; > + > + /* > + * Free and check swap_map count values corresponding to all cont= iguous > + * entries in the whole folio range. > + */ > + WARN_ON_ONCE(nr > SWAPFILE_CLUSTER); > + ci =3D lock_cluster_or_swap_info(p, start_offset); > + for (offset =3D start_offset; offset < end_offset; offset++, i++)= { > + if (data_race(p->swap_map[offset])) { > + count =3D __swap_entry_free_locked(p, offset, 1); > + if (!count) { > + bitmap_set(to_free, i, 1); > + nr_setbits++; > + } else if (count =3D=3D SWAP_HAS_CACHE) { > + *any_only_cache =3D true; > + } > + } else { > + WARN_ON_ONCE(1); > + } > + } > + unlock_cluster_or_swap_info(p, ci); > + > + /* > + * If the swap_map count values corresponding to all contiguous e= ntries are > + * all zero excluding SWAP_HAS_CACHE, the entries will be freed d= irectly by > + * skippping percpu swp_slots caches, which can avoid frequent sw= ap_info > + * locking for every individual entry. > + */ > + if (nr > 1 && nr_setbits =3D=3D nr) { > + spin_lock(&p->lock); > + swap_entry_range_free(p, entry, nr); > + spin_unlock(&p->lock); > + } else { > + for_each_set_bit(i, to_free, SWAPFILE_CLUSTER) > + free_swap_slot(swp_entry(p->type, start_offset + = i)); > + } > +} > + > static void cluster_swap_free_nr(struct swap_info_struct *sis, > unsigned long offset, int nr_pages, > unsigned char usage) > @@ -1808,6 +1860,14 @@ void free_swap_and_cache_nr(swp_entry_t entry, int= nr) > if (WARN_ON(end_offset > si->max)) > goto out; > > + /* > + * Try to free all contiguous entries about mTHP as a whole. > + */ > + if (IS_ENABLED(CONFIG_THP_SWAP) && nr > 1) { > + swap_entry_range_check_and_free(si, entry, nr, &any_only_= cache); > + goto free_cache; > + } > + > /* > * First free all entries in the range. > */ > @@ -1821,6 +1881,7 @@ void free_swap_and_cache_nr(swp_entry_t entry, int = nr) > } > } > > +free_cache: > /* > * Short-circuit the below loop if none of the entries had their > * reference drop to zero. > -- > 2.39.0 >