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Add caveat to kinfo_getvmmap(3) explaining high CPU utilisation.

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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
This commit is contained in:
Sevan Janiyan 2017-08-18 16:42:58 +00:00
parent 0b4060b073
commit 242afab281
1 changed files with 8 additions and 1 deletions
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9
lib/libutil/kinfo_getvmmap.3
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@ -25,7 +25,7 @@
.\" .\"
.\" $FreeBSD$ .\" $FreeBSD$
.\" .\"
.Dd May 27, 2015 .Dd August 18, 2017
.Dt KINFO_GETVMMAP 3 .Dt KINFO_GETVMMAP 3
.Os .Os
.Sh NAME .Sh NAME
@ -58,6 +58,13 @@ with the
mib. mib.
While the kernel returns a packed structure, this function expands the While the kernel returns a packed structure, this function expands the
data into a fixed record format. 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 .Sh RETURN VALUES
On success the On success the
.Fn kinfo_getvmmap .Fn kinfo_getvmmap