{"id":142,"date":"2023-03-01T02:54:54","date_gmt":"2023-03-01T02:54:54","guid":{"rendered":"http:\/\/example.com\/?p=134"},"modified":"2023-03-01T02:54:54","modified_gmt":"2023-03-01T02:54:54","slug":"134-mmap-read-only","status":"publish","type":"post","link":"https:\/\/w2.geleleger.nl\/rhcuk-134-mmap-read-only-esknvp\/","title":{"rendered":"Mmap Read Only"},"content":{"rendered":"<div class=\"387480d42754320bb6f0e83bf7886d44\" data-index=\"1\" style=\"float: none; margin:10px 0 10px 0; text-align:center;\">\n<script type=\"text\/javascript\">\r\n\tatOptions = {\r\n\t\t'key' : '4a1f1119f949a4af74d56b8a3af8b867',\r\n\t\t'format' : 'iframe',\r\n\t\t'height' : 250,\r\n\t\t'width' : 300,\r\n\t\t'params' : {}\r\n\t};\r\n\tdocument.write('<scr' + 'ipt type=\"text\/javascript\" src=\"http' + (location.protocol === 'https:' ? 's' : '') + ':\/\/bleedingofficecontagion.com\/4a1f1119f949a4af74d56b8a3af8b867\/invoke.js\"><\/scr' + 'ipt>');\r\n<\/script>\n<\/div>\n\n<p><strong>Mmap Read Only<\/strong>. <strong>Memory mapping only works on entire pages of memory. for mapping must be page-aligned, and length values will be rounded up. If mode == &#39;w+&#39; then shape must also be specified. &#39;c&#39; Copy-on-write: assignments affect data in memory, but changes are not saved to disk. The use case is a bunch of processes that have access to some read-only data in a shared mmap backed array. A simple mmap () readonly example Problem: You want to use mmap () from sys\/stat.h POSIX header to map a file for reading (not writing). mmap () creates a new mapping in the virtual address space of the calling process. The file on disk is read-only. The starting address for the new mapping is specified in addr. This performance improvement can be even bigger when reading a larger file.<\/strong><\/p>\n<p><figure> \t\t<img decoding=\"async\" src=\"https:\/\/image.slidesharecdn.com\/mmap-160426081701\/95\/linux-mmap-ioremap-introduction-12-638.jpg?cb=1461658652\" alt=\"Linux MMAP &amp; Ioremap introduction\" style=\"width: 100%; padding: 5px; background-color: grey;\"><figcaption>Linux MMAP &amp; Ioremap introduction (David Douglas)<\/figcaption><\/figure>\n<p> \t \t<strong>Mmap Read Only<\/strong>. <strong>Use od -CX or hexdump to see the actual contents. The portion of the file beyond end-of-file is assumed to be zero by the traditional file access APIs such as read(), readv(), write(), writev(), and ftruncate(). The system may clear a partial page, or whole pages allocated beyond end-of-file.. You can&#39;t find any simple bare example on the internet. If mode == &#39;w+&#39; then shape must also be specified. &#39;c&#39; Copy-on-write: assignments affect data in memory, but changes are not saved to disk.<\/strong> Mmap Read Only. <\/p>\n<h3>Memory-mapped files allow for multiple processes to share read-only access to a common file.<\/h3>\n<p>The use case is a bunch of processes that have access to some read-only data in a shared mmap backed array.<\/p>\n<div style=\"display: grid;grid-template-columns: auto auto auto; background: #eee; \">\n<div style=\"padding: 1em;\"> \t\t        <a href=\"https:\/\/www.detroitseniorsolution.org\/app\/uploads\/2021\/05\/mmapplacematweb-2048x1365.jpg\"><img decoding=\"async\" src=\"https:\/\/www.detroitseniorsolution.org\/app\/uploads\/2021\/05\/mmapplacematweb-2048x1365.jpg\" onerror=\"this.onerror=null;this.src='https:\/\/tse1.mm.bing.net\/th?id=OIP.562GXobA7Nwq5KcqvUZ6fgHaE7&amp;pid=Api';\" style=\"width:100%;margin-top: 8px;vertical-align: middle;\"><\/a> \t\t        <\/p>\n<p>MMAP | Agency Program | Detroit Area Agency on Aging<\/p>\n<\/p><\/div>\n<div style=\"padding: 1em;\"> \t\t        <a href=\"https:\/\/programmer.group\/images\/article\/c5d663c457be8c65ad9b84755581aa0a.jpg\"><img decoding=\"async\" src=\"https:\/\/programmer.group\/images\/article\/c5d663c457be8c65ad9b84755581aa0a.jpg\" onerror=\"this.onerror=null;this.src='https:\/\/tse4.mm.bing.net\/th?id=OIP.V-daizl7_kb7uEua0Mjb6wHaFY&amp;pid=Api';\" style=\"width:100%;margin-top: 8px;vertical-align: middle;\"><\/a> \t\t        <\/p>\n<p>[original] vma\/malloc\/mmap for Linux memory management | LaptrinhX<\/p>\n<\/p><\/div>\n<div style=\"padding: 1em;\"> \t\t        <a href=\"https:\/\/www.sublimetext.com\/screenshots\/use_mmap_with_care\/2.png\"><img decoding=\"async\" src=\"https:\/\/www.sublimetext.com\/screenshots\/use_mmap_with_care\/2.png\" onerror=\"this.onerror=null;this.src='https:\/\/tse4.mm.bing.net\/th?id=OIP.BLjqQn5uqmF-9mUcy7dkqwHaNl&amp;pid=Api';\" style=\"width:100%;margin-top: 8px;vertical-align: middle;\"><\/a> \t\t        <\/p>\n<p>Use mmap With Care &#8211; News &#8211; Sublime HQ<\/p>\n<\/p><\/div>\n<\/p><\/div>\n<div style=\"display: grid;grid-template-columns: auto auto auto; background: #eee; \">\n<div style=\"padding: 1em;\"> \t\t        <a href=\"https:\/\/i1.rgstatic.net\/publication\/268982806_Throughput_Benchmarks_mmap_versus_read\/links\/547d18290cf2cfe203c200eb\/largepreview.png\"><img decoding=\"async\" src=\"https:\/\/i1.rgstatic.net\/publication\/268982806_Throughput_Benchmarks_mmap_versus_read\/links\/547d18290cf2cfe203c200eb\/largepreview.png\" onerror=\"this.onerror=null;this.src='https:\/\/tse1.mm.bing.net\/th?id=OIP.F9Sr9A6GhB-GGiEAZLWm3gHaJl&amp;pid=Api';\" style=\"width:100%;margin-top: 8px;vertical-align: middle;\"><\/a> \t\t        <\/p>\n<p>(PDF) Throughput Benchmarks: mmap versus read<\/p>\n<\/p><\/div>\n<div style=\"padding: 1em;\"> \t\t        <a href=\"https:\/\/www.isunshare.com\/images\/article\/powerpoint-password\/unlock-read-only-powerpoint-presentation\/mark-as-final.jpg\"><img decoding=\"async\" src=\"https:\/\/www.isunshare.com\/images\/article\/powerpoint-password\/unlock-read-only-powerpoint-presentation\/mark-as-final.jpg\" onerror=\"this.onerror=null;this.src='https:\/\/tse4.mm.bing.net\/th?id=OIP.O-a59T7_Zoie6m2vYjxz3AHaDr&amp;pid=Api';\" style=\"width:100%;margin-top: 8px;vertical-align: middle;\"><\/a> \t\t        <\/p>\n<p>How to Unlock Read Only PowerPoint Presentation<\/p>\n<\/p><\/div>\n<div style=\"padding: 1em;\"> \t\t        <a href=\"http:\/\/tracertool.readthedocs.io\/en\/latest\/_images\/mmap2.jpg\"><img decoding=\"async\" src=\"http:\/\/tracertool.readthedocs.io\/en\/latest\/_images\/mmap2.jpg\" onerror=\"this.onerror=null;this.src='https:\/\/tse4.mm.bing.net\/th?id=OIP.y94MUw02VGhPRSZlORlsYQHaHU&amp;pid=Api';\" style=\"width:100%;margin-top: 8px;vertical-align: middle;\"><\/a> \t\t        <\/p>\n<p>mmap \u2014 tracer documentation<\/p>\n<\/p><\/div>\n<\/p><\/div>\n<div style=\"display: grid;grid-template-columns: auto auto auto; background: #eee; \">\n<div style=\"padding: 1em;\"> \t\t        <a href=\"https:\/\/i.gyazo.com\/f54984e9b04ab3af9755b8c3cb279011.png\"><img decoding=\"async\" src=\"https:\/\/i.gyazo.com\/f54984e9b04ab3af9755b8c3cb279011.png\" onerror=\"this.onerror=null;this.src='https:\/\/tse3.mm.bing.net\/th?id=OIP.9UmE6bBKs6-XVbjDyyeQEQHaA1&amp;pid=Api';\" style=\"width:100%;margin-top: 8px;vertical-align: middle;\"><\/a> \t\t        <\/p>\n<p>Solved 4 [15 points.] Read the manual pages on the open) and | Chegg.com<\/p>\n<\/p><\/div>\n<div style=\"padding: 1em;\"> \t\t        <a href=\"http:\/\/nineright.github.io\/images\/mmap\/linux_vm_space.jpg\"><img decoding=\"async\" src=\"http:\/\/nineright.github.io\/images\/mmap\/linux_vm_space.jpg\" onerror=\"this.onerror=null;this.src='https:\/\/tse4.mm.bing.net\/th?id=OIP.urYQRGY2ZBfP_GHwqRC2tgHaFE&amp;pid=Api';\" style=\"width:100%;margin-top: 8px;vertical-align: middle;\"><\/a> \t\t        <\/p>\n<p>mmap\u4e0eread write\u7684\u5bf9\u6bd4<\/p>\n<\/p><\/div>\n<div style=\"padding: 1em;\"> \t\t        <a href=\"https:\/\/cc.sj-cdn.net\/instructor\/1cnmfl366xu4e-guru\/courses\/1zl1mmyll8rv9\/promo-image.1597695965.png\"><img decoding=\"async\" src=\"https:\/\/cc.sj-cdn.net\/instructor\/1cnmfl366xu4e-guru\/courses\/1zl1mmyll8rv9\/promo-image.1597695965.png\" onerror=\"this.onerror=null;this.src='https:\/\/tse2.mm.bing.net\/th?id=OIP.c-tllOoE18FuJXUVQEUemgHaEa&amp;pid=Api';\" style=\"width:100%;margin-top: 8px;vertical-align: middle;\"><\/a> \t\t        <\/p>\n<p>Read-Only 201<\/p>\n<\/p><\/div>\n<\/p><\/div>\n<div style=\"display: grid;grid-template-columns: auto auto auto; background: #eee; \">\n<div style=\"padding: 1em;\"> \t\t        <a href=\"https:\/\/www.researchgate.net\/publication\/303086480\/figure\/download\/fig3\/AS:398472801996803@1472014727835\/Prevalence-of-MMAP-reads-and-methods-A-MMAP-rates-for-reads-from-mRNA-seq-and-sRNA-seq.png\"><img decoding=\"async\" src=\"https:\/\/www.researchgate.net\/publication\/303086480\/figure\/download\/fig3\/AS:398472801996803@1472014727835\/Prevalence-of-MMAP-reads-and-methods-A-MMAP-rates-for-reads-from-mRNA-seq-and-sRNA-seq.png\" onerror=\"this.onerror=null;this.src='https:\/\/tse2.mm.bing.net\/th?id=OIP.N3lZAs1aCW2Lf8qrj6nv6QHaHg&amp;pid=Api';\" style=\"width:100%;margin-top: 8px;vertical-align: middle;\"><\/a> \t\t        <\/p>\n<p>Prevalence of MMAP reads and methods. (A) MMAP rates for reads from &#8230;<\/p>\n<\/p><\/div>\n<div style=\"padding: 1em;\"> \t\t        <a href=\"https:\/\/img-blog.csdnimg.cn\/20200531161853810.png?x-oss-process=image\/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L1NDX2tpbmc=,size_16,color_FFFFFF,t_70\"><img decoding=\"async\" src=\"https:\/\/img-blog.csdnimg.cn\/20200531161853810.png?x-oss-process=image\/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L1NDX2tpbmc=,size_16,color_FFFFFF,t_70\" onerror=\"this.onerror=null;this.src='https:\/\/tse3.mm.bing.net\/th?id=OIP.AOv-9roUJtJWL4U7NUKq5QHaCr&amp;pid=Api';\" style=\"width:100%;margin-top: 8px;vertical-align: middle;\"><\/a> \t\t        <\/p>\n<p>\u4f7f\u7528mmap\u533f\u540d\u6620\u5c04\u65f6\u51fa\u73b0\u7684\u5b8f\u672a\u5b9a\u4e49___use_misc_Cheney\u8fb0\u661f\u7684\u535a\u5ba2-CSDN\u535a\u5ba2<\/p>\n<\/p><\/div>\n<div style=\"padding: 1em;\"> \t\t        <a href=\"https:\/\/linuxhint.com\/wp-content\/uploads\/2020\/07\/5-13.jpg\"><img decoding=\"async\" src=\"https:\/\/linuxhint.com\/wp-content\/uploads\/2020\/07\/5-13.jpg\" onerror=\"this.onerror=null;this.src='https:\/\/tse2.mm.bing.net\/th?id=OIP.nUG_rdosPDISVyQl1kYeZAHaCc&amp;pid=Api';\" style=\"width:100%;margin-top: 8px;vertical-align: middle;\"><\/a> \t\t        <\/p>\n<p>How to use mmap function in C language?<\/p>\n<\/p><\/div>\n<\/p><\/div>\n<p><strong>Mmap Read Only<\/strong>. <strong>If mode == &#39;w+&#39; then shape must also be specified. &#39;c&#39; Copy-on-write: assignments affect data in memory, but changes are not saved to disk. As such, only one copy of the file needs to be loaded into physical memory, even if there are thousands of programs running. As a straightforward example, the C standard library (glibc.so) is mapped into all processes running C programs. This example C program illustrates the use of mmap to map a file which has been opened read-only to memory. Memory mapping only works on entire pages of memory. for mapping must be page-aligned, and length values will be rounded up.<\/p>\n<p><\/strong> Mmap Read Only.<\/p>\n<div class=\"387480d42754320bb6f0e83bf7886d44\" data-index=\"2\" style=\"float: none; margin:10px 0 10px 0; text-align:center;\">\n<script type=\"text\/javascript\">\r\n\tatOptions = {\r\n\t\t'key' : '4a1f1119f949a4af74d56b8a3af8b867',\r\n\t\t'format' : 'iframe',\r\n\t\t'height' : 250,\r\n\t\t'width' : 300,\r\n\t\t'params' : {}\r\n\t};\r\n\tdocument.write('<scr' + 'ipt type=\"text\/javascript\" src=\"http' + (location.protocol === 'https:' ? 's' : '') + ':\/\/bleedingofficecontagion.com\/4a1f1119f949a4af74d56b8a3af8b867\/invoke.js\"><\/scr' + 'ipt>');\r\n<\/script>\n<\/div>\n\n<div style=\"font-size: 0px; height: 0px; line-height: 0px; margin: 0; padding: 0; clear: both;\"><\/div>","protected":false},"excerpt":{"rendered":"<p>Mmap Read Only. Memory mapping only works on entire pages of memory. for mapping must be page-aligned, and length values will be rounded up. If mode == &#39;w+&#39; then shape must also be specified. &#39;c&#39; Copy-on-write: assignments affect data in memory, but changes are not saved to disk. The use case is a bunch of&#8230;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/w2.geleleger.nl\/wp-json\/wp\/v2\/posts\/142"}],"collection":[{"href":"https:\/\/w2.geleleger.nl\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/w2.geleleger.nl\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/w2.geleleger.nl\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/w2.geleleger.nl\/wp-json\/wp\/v2\/comments?post=142"}],"version-history":[{"count":0,"href":"https:\/\/w2.geleleger.nl\/wp-json\/wp\/v2\/posts\/142\/revisions"}],"wp:attachment":[{"href":"https:\/\/w2.geleleger.nl\/wp-json\/wp\/v2\/media?parent=142"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/w2.geleleger.nl\/wp-json\/wp\/v2\/categories?post=142"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/w2.geleleger.nl\/wp-json\/wp\/v2\/tags?post=142"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}