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Date: Fri, 24 Jun 2016 00:10:14 -0400 (EDT)
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] Qemu and heavily increased RSS usage
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To: Peter Lieven <pl@kamp.de>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>, qemu-devel@nongnu.org, Fam Zheng <famz@redhat.com>, Peter Maydell <peter.maydell@linaro.org>


> > If it's 10M nothing.  If there is a 100M regression that is also caused
> > by RCU, we have to give up on it for that data structure, or mmap/munmap
> > the affected data structures.
> 
> If it was only 10MB I would agree. But if I run the VM described earlier
> in this thread it goes from ~35MB with Qemu-2.2.0 to ~130-150MB with
> current master. This is with coroutine pool disabled. With the coroutine pool
> it can grow to sth like 300-350MB.
> 
> Is there an easy way to determinate if RCU is the problem? I have the same
> symptoms, valgrind doesn't see the allocated memory. Is it possible
> to make rcu_call directly invoking the function - maybe with a lock around it
> that serializes the calls? Even if its expensive it might show if we search
> at the right place.

Yes, you can do that.  Just make it call the function without locks, for
a quick PoC it will be okay.

Paolo