Date: Fri, 3 Mar 2017 20:57:40 +0000 (UTC) From: Mark Johnston <markj@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r314625 - head/sys/kern Message-ID: <201703032057.v23KveoK075973@repo.freebsd.org>
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Author: markj Date: Fri Mar 3 20:57:40 2017 New Revision: 314625 URL: https://svnweb.freebsd.org/changeset/base/314625 Log: Fix a ticks comparison in sched_pctcpu_update(). We may fail to reset the %CPU tracking window if a thread does not run for over half of the ticks rollover period, resulting in a bogus %CPU value for the thread until ticks fully rolls over. Handle this by comparing the unsigned difference ticks - ts_ltick with SCHED_TICK_TARG instead. Reviewed by: cem, jeff MFC after: 1 week Sponsored by: Dell EMC Isilon Modified: head/sys/kern/sched_ule.c Modified: head/sys/kern/sched_ule.c ============================================================================== --- head/sys/kern/sched_ule.c Fri Mar 3 20:51:57 2017 (r314624) +++ head/sys/kern/sched_ule.c Fri Mar 3 20:57:40 2017 (r314625) @@ -1662,7 +1662,11 @@ sched_pctcpu_update(struct td_sched *ts, { int t = ticks; - if (t - ts->ts_ltick >= SCHED_TICK_TARG) { + /* + * The signed difference may be negative if the thread hasn't run for + * over half of the ticks rollover period. + */ + if ((u_int)(t - ts->ts_ltick) >= SCHED_TICK_TARG) { ts->ts_ticks = 0; ts->ts_ftick = t - SCHED_TICK_TARG; } else if (t - ts->ts_ftick >= SCHED_TICK_MAX) {
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