linux-kernel - Re: [accounting regression since rc1] scheduler updates

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20070821112529.GB648@elte.hu>
Date:	Tue, 21 Aug 2007 13:25:29 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Christian Borntraeger <borntraeger@...ibm.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Jan Glauber <jang@...ux.vnet.ibm.com>,
	heiko.carstens@...ibm.com, Paul Mackerras <paulus@...ba.org>
Subject: Re: [accounting regression since rc1]  scheduler updates


* Christian Borntraeger <borntraeger@...ibm.com> wrote:

> Am Montag, 20. August 2007 schrieb Ingo Molnar:
> > could you send that precise sched_clock() patch? It should be an order 
> > of magnitude simpler than the high-precision stime/utime tracking you 
> > already do, and it's needed for quality scheduling anyway.
> 
> I have a question about that. I just played with sched_clock, and even 
> when I intentionally slow down sched_clock by a factor of 2, my cpu 
> bound process gets 100 % in top. If this is intentional, I dont 
> understand how a virtualized sched_clock would fix the accounting 
> change?

could you try the patch below, does it work any better?

	Ingo

---
 kernel/sched.c |    9 +++++++++
 1 file changed, 9 insertions(+)

Index: linux/kernel/sched.c
===================================================================
--- linux.orig/kernel/sched.c
+++ linux/kernel/sched.c
@@ -333,6 +333,14 @@ static void __update_rq_clock(struct rq 
 #ifdef CONFIG_SCHED_DEBUG
 	WARN_ON_ONCE(cpu_of(rq) != smp_processor_id());
 #endif
+#ifdef CONFIG_VIRT_CPU_ACCOUNTING
+	/*
+	 * Trust sched_clock on s390:
+	 */
+	if (unlikely(delta > rq->clock_max_delta))
+		rq->clock_max_delta = delta;
+	clock += delta;
+#else
 	/*
 	 * Protect against sched_clock() occasionally going backwards:
 	 */
@@ -355,6 +363,7 @@ static void __update_rq_clock(struct rq 
 			clock += delta;
 		}
 	}
+#endif
 
 	rq->prev_clock_raw = now;
 	rq->clock = clock;
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/