* Mike Snitzer <snitzer@xxxxxxxxxx> [2010-09-09 15:15]: > On Thu, Sep 09 2010 at 3:43pm -0400, > Mike Snitzer <snitzer@xxxxxxxxxx> wrote: > > > Interestingly, just this loop: > > > > while true ; do cat /sys/block/vda/serial && date && sleep 1 ; done > > Thu Sep 9 15:29:30 EDT 2010 > > ... > > Thu Sep 9 15:31:19 EDT 2010 > > > > caused the following hang: > ... > > So it seems like the virtio requests aren't being properly cleaned up? > > Yeap, here is the result with the attached debug patch that Vivek wrote > last week to help chase this issue (which adds 'nr_requests_used'). We > thought the mpath device might be leaking requests; concern for other > devices wasn't on our radar: > > # cat /sys/block/vda/queue/nr_requests > 128 > > # while true ; do cat /sys/block/vda/queue/nr_requests_used && cat /sys/block/vda/serial && date && sleep 1 ; done > 10 > Thu Sep 9 16:04:40 EDT 2010 > 11 > Thu Sep 9 16:04:41 EDT 2010 > ... > Thu Sep 9 16:06:38 EDT 2010 > 127 > Thu Sep 9 16:06:39 EDT 2010 > 128 > > I'll have a quick look at the virtio-blk code to see if I can spot where > the request isn't getting cleaned up. But I welcome others to have a > look too (I've already spent entirely way to much time on this issue). The qemu on the host isn't new enough to handle the request. This serial attribute should have had a feature bit with it (it did at one point in one of the previous forms of the virtio-blk serial patch series, but it isn't present now) so we don't expose the attribute unless backend can handle the request type. For immediate relief, it's probably easiest to revert the kernel-side commit (or comment out the device_create_file() call after add_disk() in virtblk_probe(). -- Ryan Harper Software Engineer; Linux Technology Center IBM Corp., Austin, Tx ryanh@xxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
