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copied!<p>My understanding is as follows.<br> And I agree these numbers are hard to understand and showing inconsistent values.</p> <ul> <li><p>MemTotal</p> <pre><code>= MemFree + Active + Inactive + Slab + PageTables + VmallocUsed + X (X : alloc_pages() (get_free_pages(), etc)) </code></pre> <p>But recent kernel's vmallocused value could be wrong. This is because it counts VM_xxx regions like VM_IOREMAP, VM_MAP,... other than VM_ALLOC area. </p> <p>VM_IOREMAP region can be mapping memory which can be outside of kernel's memory management, so the formula above can be not precise, or completely wrong.</p> <p>You can either do:</p> <ul> <li>Check /proc/vmallocinfo to sort out all the entries and filter by yourself, </li> <li>Modify fs/proc/mmu.c: get_vmalloc_info() to count regions only when if(vma->flags & VM_ALLOC)</li> </ul></li> <li><p>Active + Inactive</p> <pre><code> = Buffers + Cached + SwapCached + AnonPages </code></pre></li> <li><p>AnonPages</p> <pre><code> = /proc/*/task/*/smaps anonymous area all sum (anonymous: no name|[heap]|/dev/zero|/dev/shm/*|[stack]) </code></pre> <p>Although I haven't been able to match these numbers. See <a href="https://stackoverflow.com/questions/6885107/want-to-make-smaps-output-anonymous-region-sum-and-proc-meminfo-anonpages-to-mat">here</a> and help me if you have any clue.</p></li> <li><p>Total PageCache</p> <pre><code> = Buffers + Cached + SwapCached </code></pre></li> <li><p>Slab</p> <pre><code> = SReclaimable + SUnreclaim </code></pre></li> </ul>

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