[Virtio-fs] [RFC PATCH 0/2] add stat tools for virtiofsd

[Stefan Hajnoczi]

On Fri, Aug 23, 2019 at 11:26:24AM +0100, Stefan Hajnoczi wrote:
> On Thu, Aug 22, 2019 at 10:41:48PM +0800, Gang Deng wrote:
> > On 2019/8/22 21:40, Stefan Hajnoczi wrote:
> > > On Mon, Aug 19, 2019 at 11:41:12AM +0800, Gang Deng wrote:
> > I think the difference of vtrae && qemu's tracing infrastructure looks like
> > that of /proc/diskstats(iostat) && blktrace(blkparse) for linux kernel's block
> > device. It depends on the use case. I'll measure the cost later to see whether
> > qemu's tracer can meet our needs and whether it's enough to get statistics.
> 
> Tracetool supports multiple tracers.  I suggest trying LTTng Userspace
> Tracer because it is the lowest overhead tracer (using shared memory).
> 
> https://lttng.org/docs/v2.10/#doc-lttng-ust
> 
> I don't use LTTng much so I'm not sure how to consume a live trace from
> a custom tool like vstat.  I've asked on the LTTng IRC channel and will
> let you know what the answer is.

I asked on the LTTng IRC channel and it seems they currently don't offer
a public API for processing trace events in shared memory.  This makes
writing an efficient vstat tool using LTTng harder and there probably
won't be much difference compared to other tracers.

Stefan
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