Messages in this thread | | | Date | Tue, 31 Jul 2012 09:52:30 +0900 | From | Yoshihiro YUNOMAE <> | Subject | Re: Re: Re: [RFC PATCH 0/6] virtio-trace: Support virtio-trace |
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Hi Amit,
Sorry for the late reply.
(2012/07/27 18:43), Amit Shah wrote: > On (Fri) 27 Jul 2012 [17:55:11], Yoshihiro YUNOMAE wrote: >> Hi Amit, >> >> Thank you for commenting on our work. >> >> (2012/07/26 20:35), Amit Shah wrote: >>> On (Tue) 24 Jul 2012 [11:36:57], Yoshihiro YUNOMAE wrote: >>
[...]
>>>> >>>> ***Just enhancement ideas*** >>>> - Support for trace-cmd >>>> - Support for 9pfs protocol >>>> - Support for non-blocking mode in QEMU >>> >>> There were patches long back (by me) to make chardevs non-blocking but >>> they didn't make it upstream. Fedora carries them, if you want to try >>> out. Though we want to converge on a reasonable solution that's >>> acceptable upstream as well. Just that no one's working on it >>> currently. Any help here will be appreciated. >> >> Thanks! In this case, since a guest will stop to run when host reads >> trace data of the guest, char device is needed to add a non-blocking >> mode. I'll read your patch series. Is the latest version 8? >> http://lists.gnu.org/archive/html/qemu-devel/2010-12/msg00035.html > > I suppose the latest version on-list is what you quote above. The > objections to the patch series are mentioned in Anthony's mails.
I'll check the mails.
> Hans maintains a rebased version of the patches in his tree at > > http://cgit.freedesktop.org/~jwrdegoede/qemu/ > > those patches are included in Fedora's qemu-kvm, so you can try that > out if it improves performance for you.
Thanks. I'll check those patches.
>>>> - Make "vhost-serial" >>> >>> I need to understand a) why it's perf-critical, and b) why should the >>> host be involved at all, to comment on these. >> >> a) To make collecting overhead decrease for application on a guest. >> (see above) >> b) Trace data of host kernel is not involved even if we introduce this >> patch set. > > I see, so you suggested vhost-serial only because you saw the guest > stopping problem due to the absence of non-blocking code? If so, it > now makes sense. I don't think we need vhost-serial in any way yet.
I understood. We suggested vhost-serial as one of the ideas for improving performances. Other features(trace-cmd, 9pfs, and non-blocking chardev) should be supported first, I think.
> BTW where do you parse the trace data obtained from guests? On a > remote host?
It is the best that we can parse the data on a remote host in this tracing system. Existing trace-cmd can already parse it on a remote site. If we add the feature collecting event-format data(guest's debugfs has that) from guests, we can parse tracing data on a remote host as well as on a host running guests.
Thank you,
-- Yoshihiro YUNOMAE Software Platform Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: yoshihiro.yunomae.ez@hitachi.com
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