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[36.231.187.194]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-b31f118ea01sm4658390a12.5.2025.06.21.17.44.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 21 Jun 2025 17:44:50 -0700 (PDT) From: Nick Huang To: alexs@kernel.org Cc: si.yanteng@linux.dev, dzm91@hust.edu.cn, corbet@lwn.net, akpm@linux-foundation.org, wangkefeng.wang@huawei.com, vishal.moola@gmail.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, david@redhat.com, linux-mm@kvack.org, Nick Huang Subject: [PATCH] mm/balloon_compaction: update Chinese docs for movable_ops Date: Sun, 22 Jun 2025 08:42:47 +0800 Message-ID: <20250622004249.9083-1-sef1548@gmail.com> X-Mailer: git-send-email 2.48.1 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 97DE918000A X-Stat-Signature: sx6u7s1yzobppqrrz1eg9ipr1icikz41 X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1750553092-759289 X-HE-Meta: U2FsdGVkX1/szB1OWRwebDvmQNWjw/42+AIU0y8hYlYCGjFZ4WUEw/hbcF9FPrYLP+xAb5N7S8lWC4EFb8tLlY2ilrbu/r7fcUsUXUSmgnUoSCicDd3IZjFen7+tSipGTvFwwUiS9c60nLXWlu9lYE+PoyD+kygE0oy5ZQU2CB9cIuCDXs3kujCZ7WLHqZDMFAWH3cuK+21HG2l1VIK7Hec+3XMy0FDK+qciHMHAuvHB3m4yhskPIUunryDom03V/hDQHHGrjdPQ0gB2JvRxt/s1J9r0bavRBPn7Xj/Ue2AI3FYaeqdpvkxh3rc/LIvtbaO+8lu1mTZVAtNRraDzHtfbPvAT4UgBbEvNTzW+eU2iUaTseMWsjus7OC+pe3GqSTzOufXEO9XHtVla+hDfYcDcKtenGv4V4au5JEAjnCIECjSx1R0FlEYSmkSDA7MSsiuk58uC8c90hF55PbV5LKScXzS7LLtMPiv+DSLGYBrS9C/hrhnfC5H89d/YuWqfI0TBIkfq6R/e9iL/8QkAsMGmDSjZotHQhCA/blHFvgIKoh8MmpPq2I5SgrWE5Q/iux2XfI9MgQUjv4mTBGBKkk0zicrUUxvooqbEzJi5r8dOI5LopCDdXkJ9fCWFewSq6Gi+Oq7KLrkP6B2oqXQcLkXOFcvD+cd3g01SHCwzyKHcPbUmP4UI1mt6mZF6/gRCb9UOZzsXxTVt2cyr2BAi2QMoTq+UXTOrjmtOpEfjfO2CLMheFNUw9fiSoM9Y+3dXLDfr6pbxutSU5FeMOnTTQX4GB+8Leoo1a+DVCZ0YrmDYRnnNYhSkyVhxeQE4NAfXjniQCmXx1JBVg3tPc6scfeg4e/B0g2bG5BXLGfXwZ4JllkGjDflfe6siquK8fXQGSuWRxwEnFALOqyEkjRRgMoBzMFvMRW4QpZMYLMW5IGtQEitiFM1bv1Bj85sIZZhh3GyMllWIC9d3KXiTD8/ 14xXsi0k 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 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: Remove Non-LRU Page Migration and Add Movable_ops Page Migration Reference: https://lore.kernel.org/all/20250618174014.1168640-28-david@redhat.com/ --- .../translations/zh_CN/mm/page_migration.rst | 88 +++---------------- 1 file changed, 10 insertions(+), 78 deletions(-) diff --git a/Documentation/translations/zh_CN/mm/page_migration.rst b/Documentation/translations/zh_CN/mm/page_migration.rst index 8c8461c6cb9f..e4f03228dbd9 100644 --- a/Documentation/translations/zh_CN/mm/page_migration.rst +++ b/Documentation/translations/zh_CN/mm/page_migration.rst @@ -114,91 +114,23 @@ migrate_pages()对它的页面列表进行了多次处理。如果当时对一 18. 新的页面被移到LRU中，可以被交换器等再次扫描。 -非LRU页面迁移 +movable_ops 页面迁移 ============= -尽管迁移最初的目的是为了减少NUMA的内存访问延迟，但压缩也使用迁移来创建高阶页面。 +选定的特定类型且非 folio 的页面（例如 memory balloon 或 zsmalloc 分配的页面）可以借助 movable_ops 迁移框架实现页面迁移。 -目前实现的问题是，它被设计为只迁移*LRU*页。然而，有一些潜在的非LRU页面可以在驱动中 -被迁移，例如，zsmalloc，virtio-balloon页面。 +struct movable_operations 提供了与页面类型相关的回调函数，用于隔离、迁移以及将页面放回。 -对于virtio-balloon页面，迁移代码路径的某些部分已经被钩住，并添加了virtio-balloon -的特定函数来拦截迁移逻辑。这对一个驱动来说太特殊了，所以其他想让自己的页面可移动的驱 -动就必须在迁移路径中添加自己的特定钩子。 +一旦页面被标记为具有 movable_ops，在页面被释放回 buddy 系统之前，不应更改其状态。这包括不得更改或清除页面类型，也不得更改或清除 PG_movable_ops 页面标志。 -为了克服这个问题，VM支持非LRU页面迁移，它为非LRU可移动页面提供了通用函数，而在迁移 -路径中没有特定的驱动程序钩子。 +目前，任意驱动程序尚无法直接使用此框架，因为使用该机制需满足以下条件： -如果一个驱动程序想让它的页面可移动，它应该定义三个函数，这些函数是 -struct address_space_operations的函数指针。 +(a) 页面类型； +(b) 在 page_has_movable_ops() 中根据页面类型标示这些页面可能具有 movable_ops； +(c) 在 page_has_movable_ops() 中根据页面类型返回对应的 movable_ops； +(d) 不得将 PG_movable_ops 和 PG_movable_ops_isolated 页面标志用于其他用途。 -1. ``bool (*isolate_page) (struct page *page, isolate_mode_t mode);`` - - VM对驱动的isolate_page()函数的期望是，如果驱动成功隔离了该页，则返回*true*。 - 返回true后，VM会将该页标记为PG_isolated，这样多个CPU的并发隔离就会跳过该 - 页进行隔离。如果驱动程序不能隔离该页，它应该返回*false*。 - - 一旦页面被成功隔离，VM就会使用page.lru字段，因此驱动程序不应期望保留这些字段的值。 - -2. ``int (*migratepage) (struct address_space *mapping,`` -| ``struct page *newpage, struct page *oldpage, enum migrate_mode);`` - - 隔离后，虚拟机用隔离的页面调用驱动的migratepage()。migratepage()的功能是将旧页 - 的内容移动到新页，并设置struct page newpage的字段。请记住，如果你成功迁移了旧页 - 并返回MIGRATEPAGE_SUCCESS，你应该通过page_lock下的__ClearPageMovable()向虚 - 拟机表明旧页不再可移动。如果驱动暂时不能迁移该页，驱动可以返回-EAGAIN。在-EAGAIN - 时，VM会在短时间内重试页面迁移，因为VM将-EAGAIN理解为 "临时迁移失败"。在返回除 - -EAGAIN以外的任何错误时，VM将放弃页面迁移而不重试。 - - 在migratepage()函数中，驱动程序不应该接触page.lru字段。 - -3. ``void (*putback_page)(struct page *);`` - - 如果在隔离页上迁移失败，VM应该将隔离页返回给驱动，因此VM用隔离页调用驱动的 - putback_page()。在这个函数中，驱动应该把隔离页放回自己的数据结构中。 - -非LRU可移动页标志 - - 有两个页面标志用于支持非LRU可移动页面。 - - * PG_movable - - 驱动应该使用下面的函数来使页面在page_lock下可移动。:: - - void __SetPageMovable(struct page *page, struct address_space *mapping) - - 它需要address_space的参数来注册将被VM调用的migration family函数。确切地说， - PG_movable不是struct page的一个真正的标志。相反，VM复用了page->mapping的低 - 位来表示它:: - - #define PAGE_MAPPING_MOVABLE 0x2 - page->mapping = page->mapping | PAGE_MAPPING_MOVABLE; - - 所以驱动不应该直接访问page->mapping。相反，驱动应该使用page_mapping()，它可 - 以在页面锁下屏蔽掉page->mapping的低2位，从而获得正确的struct address_space。 - - 对于非LRU可移动页面的测试，VM支持__PageMovable()函数。然而，它并不能保证识别 - 非LRU可移动页面，因为page->mapping字段与struct page中的其他变量是统一的。如 - 果驱动程序在被虚拟机隔离后释放了页面，尽管page->mapping设置了PAGE_MAPPING_MOVABLE， - 但它并没有一个稳定的值（看看__ClearPageMovable）。但是__PageMovable()在页 - 面被隔离后，无论页面是LRU还是非LRU可移动的，调用它开销都很低，因为LRU页面在 - page->mapping中不可能有PAGE_MAPPING_MOVABLE设置。在用pfn扫描中的lock_page() - 进行更大开销的检查来选择受害者之前，它也很适合只是瞥一眼来测试非LRU可移动的页面。 - - 为了保证非LRU的可移动页面，VM提供了PageMovable()函数。与__PageMovable()不 - 同，PageMovable()在lock_page()下验证page->mapping和 - mapping->a_ops->isolate_page。lock_page()可以防止突然破坏page->mapping。 - - 使用__SetPageMovable()的驱动应该在释放页面之前通过page_lock()下的 - __ClearMovablePage()清除该标志。 - - * PG_isolated - - 为了防止几个CPU同时进行隔离，VM在lock_page()下将隔离的页面标记为PG_isolated。 - 因此，如果一个CPU遇到PG_isolated非LRU可移动页面，它可以跳过它。驱动程序不需要 - 操作这个标志，因为VM会自动设置/清除它。请记住，如果驱动程序看到PG_isolated页， - 这意味着该页已经被VM隔离，所以它不应该碰page.lru字段。PG_isolated标志与 - PG_reclaim标志是同义的，所以驱动程序不应该为自己的目的使用PG_isolated。 +例如: Balloon 驱动程序可以通过核心内核提供的 balloon-compaction 框架使用该机制。 监测迁移 ======== -- 2.48.1