Hi Steven, Thank you for reviewing my patches. Sorry for the late reply.
(2013/08/21 1:00), Steven Rostedt wrote:
On Mon, 19 Aug 2013 18:46:20 +0900 Yoshihiro YUNOMAE <yoshihiro.yunomae...@hitachi.com> wrote:d) merge feature of trace data of multiple guests and a host in chronological order Current trace-cmd cannot merge trace data of multiple guests and a host in chronological order. If an user wants to analyze an I/O delay problem of a guest, the user will want to check trace data of all guests and the host in a file. However, trace-cmd does not support a merge feature yet, the user must make a merging script. So, trace-cmd had better support a merge feature for multiple files for virtualization.This is incorrect. trace-cmd already has a merge feature for multiple machines. If you have two boxes that are in sync by ntp, you can do the following: On box1: trace-cmd record --date -o trace-box1.dat -e all ping box2 On box2: trace-cmd record --date -o trace-box2.dat -e all ping box1 And then copy over trace-box2.dat to box1 and run trace-cmd report -i trace-box1.dat -i trace-box2.dat And you will see a merge. I just did this on two of my boxes called ixf and bxtest and here's a partial output: trace-bxtest.dat: trace-cmd-1348 [003] 1377013771.682807: sys_enter: NR 2 (22e2b00, 241, 1a4, 1a, 4361ac, 3) trace-bxtest.dat: trace-cmd-1348 [003] 1377013771.682808: sys_enter_open: filename: 0x022e2b00, flags: 0x00000241, mode: 0x000001a4 trace-ixf.dat: <idle>-0 [002] 1377013771.682808: hrtimer_cancel: hrtimer=0xffff880002110820 trace-ixf.dat: <idle>-0 [002] 1377013771.682808: hrtimer_expire_entry: hrtimer=0xffff880002110820 now=673528250850 function=tick_sched_timer/0x0 trace-bxtest.dat: trace-cmd-1348 [003] 1377013771.682809: kmem_cache_alloc: (getname_flags+0x37) call_site=ffffffff8117b797 ptr=0xffff8800d38c0000 bytes_req=4096 bytes_alloc=4096 gfp_flags=GFP_KERNELGFP_NOTRACK The --date option is used because the two machines are not in sync with the trace time stamp. What the date option does, is to sync the timestamp up with the gettimeofday and the output reports that. This allows the two boxes to report information that is relatively close to how the two interacted.
Oh, I didn't know the --date option. As you mentioned, we can merge trace data in chronological order by using --date option if the times of those machines are synchronized by NTP.
If the guest and the host have the same clock, then the --date option is not needed and the two should be able to be merged normally.
No, we can not assure that the guest and the host have the same clock even if it is running on the same physical machine, because both kernel doesn't share it, there is some difference between them. So, we still need time synchronizing guest-host by NTP and --date option. However, there are cases that times of those machines cannot be synchronized. For example, although multiple users can run guests on virtualization environments (e.g. multi-tenant cloud hosting), there are no guarantee that they use the same NTP server. Moreover, even if the times are synchronized, trace data cannot exactly be merged because the NTP-synchronized time granularity may not be enough fine for sorting guest-host switching events.
Also, I haven't released it yet (will soon), but trace-cmd handles multiple buffers too. That is, with the multiple buffers that ftrace has, it will create and read from them as well as report them.
Is it commit ID d56f30679f9811a91ed471c8e081cc7ffbed1e62? We can download the feature from your git repository.
I'll finish my testing on all the latest features of trace-cmd I have and push it out later today. I'll also take a look at the rest of your patches.
Thank you! Yoshihiro YUNOMAE -- Yoshihiro YUNOMAE Software Platform Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: yoshihiro.yunomae...@hitachi.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
