On Tue, Apr 20, 2021 at 02:24:30PM +0100, Matthew Wilcox wrote: > On Tue, Apr 20, 2021 at 03:13:54PM +0300, Mike Rapoport wrote: > > Add a paragraph that explains that it may happen that the counters in > > /proc/meminfo do not add up to the overall memory usage. > > ... that is, the sum may be lower because memory is allocated for other > purposes that is not reported here, right? > > Is it ever possible for it to be higher? Maybe due to a race when > sampling the counters? > > > Provides information about distribution and utilization of memory. This > > -varies by architecture and compile options. The following is from a > > -16GB PIII, which has highmem enabled. You may not have all of these fields. > > +varies by architecture and compile options. Please note that it may happen > > +that the memory accounted here does not add up to the overall memory usage > > +and the difference for some workloads can be substantial. In many cases there > > +are other means to find out additional memory using subsystem specific > > +interfaces, for instance /proc/net/sockstat for TCP memory allocations. > > How about just: > > +varies by architecture and compile options. The memory reported here > +may not add up to the overall memory usage and the difference for some > +workloads can be substantial. [...] I like this. I also for adding a sentence about overlap in the counters: +varies by architecture and compile options. Some of the counters reported +here overlap. The memory reported by the non overlapping counters may not +add up to the overall memory usage and the difference for some workloads can be substantial. [...] > But I'd like to be a bit more explicit about the reason, hence my question > above to be sure I understand. > > It's also not entirely clear which of the fields in meminfo can be > usefully summed. VmallocTotal is larger than MemTotal, for example. > But I know that KernelStack is allocated through vmalloc these days, > and I don't know whether VmallocUsed includes KernelStack or whether I > can sum them. Similarly, is Mlocked a subset of Unevictable? > > There is some attempt at explaining how these numbers fit together, but > it's outdated, and doesn't include Mlocked, Unevictable or KernelStack Fixing the outdated docs and adding more detailed explanation is obviously welcome, but it's beyond the scope of the current patch. -- Sincerely yours, Mike.
