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Re: [Xen-devel] [PATCH 1/5] xentrace_format: print timestamps in nanoseconds


  • To: Andrii Anisov <andrii_anisov@xxxxxxxx>, Andrii Anisov <andrii.anisov@xxxxxxxxx>, <xen-devel@xxxxxxxxxxxxx>
  • From: George Dunlap <george.dunlap@xxxxxxxxxx>
  • Date: Tue, 11 Sep 2018 11:44:26 +0100
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  • Cc: George Dunlap <george.dunlap@xxxxxxxxxxxxx>, Wei Liu <wei.liu2@xxxxxxxxxx>, Ian Jackson <ian.jackson@xxxxxxxxxxxxx>, Dario Faggioli <dfaggioli@xxxxxxxx>
  • Delivery-date: Tue, 11 Sep 2018 10:44:34 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
  • Openpgp: preference=signencrypt

On 09/11/2018 11:32 AM, Andrii Anisov wrote:
> Hello George,
> 
> 
> On 11.09.18 13:15, George Dunlap wrote:
>>>           if mhz:
>>> -            tsc = tsc / (mhz*1000000.0)
>>> +            tsc = tsc * 1000.0 / mhz
>> Why do you prefer this?
> I'm playing with scheduling from one hand, so time stamps in seconds
> does not give understanding about what's going on.
> From other hand I'm quite confused about how useful timestamps in
> seconds could be for traces. As per my understanding, tracer should be
> useful for debugging some rapidly changing processes.

Oh, sorry -- I missed the point of this patch.

---
xentrace_format: print timestamps in nanoseconds

...rather than seconds.  Having timestamps for rapidly-occurring events
in nanoseconds makes it easier to understand what's going on.

While here, document the -c option.
---

What I do in xenalyze is to have the timestamps in seconds, but always
print down to the nanosecond.  (For this I actually break cpu cycles
into s and ns separately, and then print "%u.%09u".)

But this is also fine with me.

 -George

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