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[111.250.2.155]) by smtp.gmail.com with ESMTPSA id 8-20020a17090a174800b001c7d8b160f0sm10526637pjm.51.2022.03.28.02.59.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 28 Mar 2022 02:59:23 -0700 (PDT) From: Yanteng Si X-Google-Original-From: Yanteng Si To: corbet@lwn.net, alexs@kernel.org, seakeel@gmail.com Cc: Yanteng Si , chenhuacai@kernel.org, jiaxun.yang@flygoat.com, linux-doc@vger.kernel.org, Yanteng Si Subject: [PATCH v3 12/12] docs/zh_CN: add vm zsmalloc translation Date: Mon, 28 Mar 2022 17:59:54 +0800 Message-Id: <6c59cb90bd1ba8e7042c8c587887dbe34e524d99.1648458742.git.siyanteng@loongson.cn> X-Mailer: git-send-email 2.27.0 In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org From: Yanteng Si Translate .../vm/zsmalloc.rst into Chinese. Signed-off-by: Yanteng Si Reviewed-by: Alex Shi --- Documentation/translations/zh_CN/vm/index.rst | 2 +- .../translations/zh_CN/vm/zsmalloc.rst | 78 +++++++++++++++++++ 2 files changed, 79 insertions(+), 1 deletion(-) create mode 100644 Documentation/translations/zh_CN/vm/zsmalloc.rst diff --git a/Documentation/translations/zh_CN/vm/index.rst b/Documentation/translations/zh_CN/vm/index.rst index e28d0e919bfe..c7148125e659 100644 --- a/Documentation/translations/zh_CN/vm/index.rst +++ b/Documentation/translations/zh_CN/vm/index.rst @@ -38,6 +38,7 @@ TODO:待引用文档集被翻译完毕后请及时修改此处） remap_file_pages split_page_table_lock z3fold + zsmalloc TODOLIST: * arch_pgtable_helpers @@ -50,4 +51,3 @@ TODOLIST: * transhuge * unevictable-lru * vmalloced-kernel-stacks -* zsmalloc diff --git a/Documentation/translations/zh_CN/vm/zsmalloc.rst b/Documentation/translations/zh_CN/vm/zsmalloc.rst new file mode 100644 index 000000000000..29e9c70a8eb6 --- /dev/null +++ b/Documentation/translations/zh_CN/vm/zsmalloc.rst @@ -0,0 +1,78 @@ +:Original: Documentation/vm/zs_malloc.rst + +:翻译: + + 司延腾 Yanteng Si + +:校译: + +======== +zsmalloc +======== + +这个分配器是为与zram一起使用而设计的。因此，该分配器应该在低内存条件下工作良好。特别是， +它从未尝试过higher order页面的分配，这在内存压力下很可能会失败。另一方面，如果我们只 +是使用单（0-order）页，它将遭受非常高的碎片化 - 任何大小为PAGE_SIZE/2或更大的对象将 +占据整个页面。这是其前身（xvmalloc）的主要问题之一。 + +为了克服这些问题，zsmalloc分配了一堆0-order页面，并使用各种"struct page"字段将它 +们链接起来。这些链接的页面作为一个单一的higher order页面，即一个对象可以跨越0-order +页面的边界。代码将这些链接的页面作为一个实体，称为zspage。 + +为了简单起见，zsmalloc只能分配大小不超过PAGE_SIZE的对象，因为这满足了所有当前用户的 +要求（在最坏的情况下，页面是不可压缩的，因此以"原样"即未压缩的形式存储）。对于大于这 +个大小的分配请求，会返回失败（见zs_malloc）。 + +此外，zs_malloc()并不返回一个可重复引用的指针。相反，它返回一个不透明的句柄（无符号 +长），它编码了被分配对象的实际位置。这种间接性的原因是zsmalloc并不保持zspages的永久 +映射，因为这在32位系统上会导致问题，因为内核空间映射的VA区域非常小。因此，在使用分配 +的内存之前，对象必须使用zs_map_object()进行映射以获得一个可用的指针，随后使用 +zs_unmap_object()解除映射。 + +stat +==== + +通过CONFIG_ZSMALLOC_STAT，我们可以通过 ``/sys/kernel/debug/zsmalloc/`` +看到zsmalloc内部信息。下面是一个统计输出的例子。:: + + # cat /sys/kernel/debug/zsmalloc/zram0/classes + + class size almost_full almost_empty obj_allocated obj_used pages_used pages_per_zspage + ... + ... + 9 176 0 1 186 129 8 4 + 10 192 1 0 2880 2872 135 3 + 11 208 0 1 819 795 42 2 + 12 224 0 1 219 159 12 4 + ... + ... + + +class + 索引 +size + zspage存储对象大小 +almost_empty + ZS_ALMOST_EMPTY zspage的数量（见下文）。 +almost_full + ZS_ALMOST_FULL zspage的数量(见下图) +obj_allocated + 已分配对象的数量 +obj_used + 分配给用户的对象的数量 +pages_used + 为该类分配的页数 +pages_per_zspage + 组成一个zspage的0-order页面的数量 + +当n <= N / f时，我们将一个zspage分配给ZS_ALMOST_EMPTYfullness组，其中 + +* n = 已分配对象的数量 +* N = zspage可以存储的对象总数 +* f = fullness_threshold_frac(即，目前是4个) + +同样地，我们将zspage分配给: + +* ZS_ALMOST_FULL when n > N / f +* ZS_EMPTY when n == 0 +* ZS_FULL when n == N -- 2.27.0