I noticed that statm's "shared" field doesn't match the sum of all the
"shared" entries in smaps [1].
The kernel docs explain that statm's "shared" field is "number of
pages that are shared (i.e. backed by a file)" [2]. smaps appears to
call a page shared if it's mapped by at least two processes, which
explains this discrepancy.
I'm not a kernel hacker, but it appears to me they do mean "i.e." and
not "e.g." in the statm description: In
fs/proc/task_mmu.c::task_statm, I see
*shared = get_mm_counter(mm, MM_FILEPAGES);
Here's a patch which updates the man page to match the (hopefully
correct) kernel docs.
Subject: [PATCH] proc.5: statm's "shared" field refers to pages backed by
files.
---
man5/proc.5 | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/man5/proc.5 b/man5/proc.5
index 88af7c5..855a2e0 100644
--- a/man5/proc.5
+++ b/man5/proc.5
@@ -947,7 +947,7 @@ size total program size
(same as VmSize in \fI/proc/[pid]/status\fP)
resident resident set size
(same as VmRSS in \fI/proc/[pid]/status\fP)
-share shared pages (from shared mappings)
+share shared pages (i.e., backed by a file)
text text (code)
.\" (not including libs; broken, includes data segment)
lib library (unused in Linux 2.6)
--
1.7.10.4
I've also attached the patch in case gmail messes it up somehow.
-Justin
[1] https://bugzilla.mozilla.org/show_bug.cgi?id=807181
[2] http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=blob;f=Documentation/filesystems/proc.txt;h=a1793d670cd01bd374eddf54ffdfc768504291ff;hb=HEAD
Attachment:
0001-proc.5-statm-s-shared-field-refers-to-pages-backed-b.patch
Description: Binary data
