From mboxrd@z Thu Jan 1 00:00:00 1970 From: compudj@krystal.dyndns.org (Mathieu Desnoyers) Date: Wed, 3 Nov 2010 11:13:37 -0400 Subject: [ltt-dev] Problem on combine kernel trace and userspace trace. In-Reply-To: References: Message-ID: <20101103151336.GA17967@Krystal> * Sam Liao (phyomh at gmail.com) wrote: > Hi, > > I'm trying to combine the kernel trace and userspace trace, and it > seems that the > the userspace events can not be recognized to the right process with the kernel > events. I'm not sure if this is a problem of timestamp between kernel > and userspace. > > Here is the environment I'm using: > ---- > Linux Trace Toolkit Visualizer 0.12.35-20082010 > linux kernel 2.6.34.6 > ust-0.4. ( I update the clock to use clock_gettime). If you are on x86 or powerpc, using the clock source that does not use clock_gettime would directly read the timestamp counter value, which should work. Make sure your architecture (on x86) has synchronized contant TSCs. LTTng complains about using a work-around in dmesg if it is not the case. If lttng uses the workaround on x86, then there is currently no mean to gather synchronized ust-lttng traces. As Julien said, we're currently working on a vdso solution to make this all work. Thanks, Mathieu > ---- > > Is there anything I missed? Also I'm thinking about one problem, if > ust using clock_gettime to > get the nonseconds timestamp which is actually the timestamp that the user > application is doing the clock_gettime system call instead the > userspace event, how ust > deal with such difference and get this fixed when trace combination? > > Thanks, > -Sam > > _______________________________________________ > ltt-dev mailing list > ltt-dev at lists.casi.polymtl.ca > http://lists.casi.polymtl.ca/cgi-bin/mailman/listinfo/ltt-dev > -- Mathieu Desnoyers Operating System Efficiency R&D Consultant EfficiOS Inc. http://www.efficios.com