Date: Thu, 20 Sep 2012 11:56:15 -0400 (EDT) From: Ben Wilber <ben@desync.com> To: FreeBSD-gnats-submit@FreeBSD.org Subject: kern/171811: [patch] rctl(8) cputime is too high Message-ID: <20120920155615.0B46B2D92@exile.desync.com> Resent-Message-ID: <201209201600.q8KG0NQM037081@freefall.freebsd.org>
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>Number: 171811
>Category: kern
>Synopsis: [patch] rctl(8) cputime is too high
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Thu Sep 20 16:00:22 UTC 2012
>Closed-Date:
>Last-Modified:
>Originator: Ben Wilber
>Release: FreeBSD 10.0-CURRENT amd64
>Organization:
>Environment:
System: FreeBSD exile 10.0-CURRENT FreeBSD 10.0-CURRENT #1 r240178M: Thu Sep 6 19:25:33 EDT 2012 bw@exodus:/usr/obj/usr/src/sys/COMRADE amd64
>Description:
rctl's idea of cputime is unreasonably high with lots of process turnover.
>How-To-Repeat:
# jail -c command=sh
jail# while true; do id > /dev/null; done
meanwhile:
# dtrace -n 'rusage:add-cred/args[0]->cr_prison->pr_id != 0 && args[1] == 0/{printf("%d: jail %d cputime %d", pid, args[0]->cr_prison->pr_id, args[2])}'
5 57139 rusage:add-cred 37375: jail 5 cputime 124211
5 57139 rusage:add-cred 37375: jail 5 cputime 6330
5 57139 rusage:add-cred 37375: jail 5 cputime 51237828
5 57139 rusage:add-cred 37375: jail 5 cputime 173602
5 57139 rusage:add-cred 37375: jail 5 cputime 6834680
(...)
>Fix:
Attached patch seems to help.
--- kern_racct.diff begins here ---
Index: kern_racct.c
===================================================================
diff --git a/head/sys/kern/kern_racct.c b/head/sys/kern/kern_racct.c
--- a/head/sys/kern/kern_racct.c (revision 240705)
+++ b/head/sys/kern/kern_racct.c (working copy)
@@ -607,7 +607,9 @@
/*
* We don't need to calculate rux, proc_reap() has already done this.
*/
+ PROC_SLOCK(p);
runtime = cputick2usec(p->p_rux.rux_runtime);
+ PROC_SUNLOCK(p);
#ifdef notyet
KASSERT(runtime >= p->p_prev_runtime, ("runtime < p_prev_runtime"));
#else
--- kern_racct.diff ends here ---
>Release-Note:
>Audit-Trail:
>Unformatted:
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