docs: proc.rst: meminfo: briefly describe gaps in memory accounting

Add a paragraph that explains that it may happen that the counters in /proc/meminfo do not add up to the overall memory usage. Link: https://lkml.kernel.org/r/[email protected] Signed-off-by: Mike Rapoport <[email protected]> Acked-by: Michal Hocko <[email protected]> Reviewed-by: Matthew Wilcox (Oracle) <[email protected]> Acked-by: Vlastimil Babka <[email protected]> Cc: Jonathan Corbet <[email protected]> Cc: Alexey Dobriyan <[email protected]> Cc: Eric Dumazet <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
niw · Jul 1, 2021 · 8d719af · 8d719af
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commit 8d719af
Showing 1 changed file with 9 additions and 2 deletions.
diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
@@ -933,8 +933,15 @@ meminfo
 ~~~~~~~
 
 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.  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.  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.
+
+The following is from a 16GB PIII, which has highmem enabled.
+You may not have all of these fields.
 
 ::