Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750979AbZCTI2Z (ORCPT ); Fri, 20 Mar 2009 04:28:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753524AbZCTI2M (ORCPT ); Fri, 20 Mar 2009 04:28:12 -0400 Received: from fxip-0047f.externet.hu ([88.209.222.127]:51094 "EHLO pomaz-ex.szeredi.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752823AbZCTI2L (ORCPT ); Fri, 20 Mar 2009 04:28:11 -0400 To: peterz@infradead.org CC: miklos@szeredi.hu, roland@redhat.com, efault@gmx.de, rjw@sisk.pl, jdike@addtoit.com, mingo@elte.hu, user-mode-linux-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org In-reply-to: <1237537169.24626.29.camel@twins> (message from Peter Zijlstra on Fri, 20 Mar 2009 09:19:29 +0100) Subject: Re: [patch] fix uml slowness caused by ptrace preemption bug on host References: <1237537169.24626.29.camel@twins> Message-Id: From: Miklos Szeredi Date: Fri, 20 Mar 2009 09:27:10 +0100 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1080 Lines: 29 On Fri, 20 Mar 2009, Peter Zijlstra wrote: > On Thu, 2009-03-19 at 23:23 +0100, Miklos Szeredi wrote: > > > > This patch solves this by not scheduling on preempt_enable() after > > ptrace_stop() has woken up the tracer. > > Nice,.. however did you find this? Ftrace helped a lot, it's a really cool tool :). I had to patch it with this, otherwise the timestamps would be totally off: diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index bd38c5c..557c2dd 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -108,7 +108,7 @@ u64 ring_buffer_time_stamp(int cpu) preempt_disable_notrace(); /* shift to debug/test normalization and TIME_EXTENTS */ - time = sched_clock() << DEBUG_SHIFT; + time = cpu_clock(cpu) << DEBUG_SHIFT; preempt_enable_no_resched_notrace(); return time; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/