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From: Sevan Janiyan <sevan@FreeBSD.org>
Date: Fri, 18 Aug 2017 16:42:58 +0000 (UTC)
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Subject: svn commit: r322665 - head/lib/libutil
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Author: sevan (doc committer)
Date: Fri Aug 18 16:42:58 2017
New Revision: 322665
URL: https://svnweb.freebsd.org/changeset/base/322665

Log:
  Add caveat to kinfo_getvmmap(3) explaining high CPU utilisation.
  Based on kib's reply on https://lists.freebsd.org/pipermail/freebsd-hackers/2016-July/049710.html
  
  PR:		210904
  Submitted by:	Yuri Victorovich <yuri AT rawbw DOT com>
  Reviewed by:	jilles
  Approved by:	bcr (mentor)
  MFC after:	5 days
  Differential Revision:	https://reviews.freebsd.org/D12004

Modified:
  head/lib/libutil/kinfo_getvmmap.3

Modified: head/lib/libutil/kinfo_getvmmap.3
==============================================================================
--- head/lib/libutil/kinfo_getvmmap.3	Fri Aug 18 16:38:33 2017	(r322664)
+++ head/lib/libutil/kinfo_getvmmap.3	Fri Aug 18 16:42:58 2017	(r322665)
@@ -25,7 +25,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd May 27, 2015
+.Dd August 18, 2017
 .Dt KINFO_GETVMMAP 3
 .Os
 .Sh NAME
@@ -58,6 +58,13 @@ with the
 mib.
 While the kernel returns a packed structure, this function expands the
 data into a fixed record format.
+.Sh CAVEAT
+.Fn kinfo_getvmmap
+calls can cause significant CPU consumption because calculating the residency
+counts requires iterating over all memory pages of the process.
+Setting the sysctl variable
+.Va kern.proc_vmmap_skip_resident_count
+to 1 prevents this calculation.
 .Sh RETURN VALUES
 On success the
 .Fn kinfo_getvmmap