[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] Re: Need help with fixing the Xen waitqueue feature
Olaf, are waitqueue's on the mem-event ring meant to be the way to deal with ring exhaustion? i.e. is this meant to go beyond a testing vehicle for waitqueue's? With the pager itself generating events, and foreign mappings generating events, you'll end up putting dom0 vcpu's in a waitqueue. This will basically deadlock the host. Am I missing something here? Andres > Date: Tue, 8 Nov 2011 22:20:24 +0100 > From: Olaf Hering <olaf@xxxxxxxxx> > Subject: [Xen-devel] Need help with fixing the Xen waitqueue feature > To: xen-devel@xxxxxxxxxxxxxxxxxxx > Message-ID: <20111108212024.GA5276@xxxxxxxxx> > Content-Type: text/plain; charset=utf-8 > > > The patch 'mem_event: use wait queue when ring is full' I just sent out > makes use of the waitqueue feature. There are two issues I get with the > change applied: > > I think I got the logic right, and in my testing vcpu->pause_count drops > to zero in p2m_mem_paging_resume(). But for some reason the vcpu does > not make progress after the first wakeup. In my debugging there is one > wakeup, the ring is still full, but further wakeups dont happen. > The fully decoded xentrace output may provide some hints about the > underlying issue. But its hard to get due to the second issue. > > Another thing is that sometimes the host suddenly reboots without any > message. I think the reason for this is that a vcpu whose stack was put > aside and that was later resumed may find itself on another physical > cpu. And if that happens, wouldnt that invalidate some of the local > variables back in the callchain? If some of them point to the old > physical cpu, how could this be fixed? Perhaps a few "volatiles" are > needed in some places. > > I will check wether pinning the guests vcpus to physical cpus actually > avoids the sudden reboots. > > Olaf > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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