virsh dump blocking problem

Hi all,

I'm not sure whether it's appropriate to post the problem here. I played with "virsh" under Fedora 12, and started a KVM fedora12 guest by "virsh start" command. The fedora12 guest is successfully started. Than I run the following command to dump the guest core:
#virsh dump 1 mycoredump (domain id is 1)

This command seemed blocking and not return. According to he strace output, virsh dump seems that it's blocking at poll() call. I think the following should be the call trace of virsh.

cmdDump()
-> virDomainCoreDump()

    -> remoteDomainCoreDump()
         -> call()
             -> remoteIO()
                 -> remoteIOEventLoop()
                      -> poll(fds, ARRAY_CARDINALITY(fds), -1)

Any one encounters this problem also, any thoughts?

Thanks
Gui

I met and it seems qemu-kvm continues to counting the number of dirty pages and does no answer to libvirt. Guest never work and I have to kill it.

I met this with 2.6.32+ qemu-0.12.3+ libvirt 0.7.7.1.
When I updated the host kernel to 2.6.33, qemu-kvm never work. So, I moved back to fedora12's latest qemu-kvm.

Now, 2.6.34-rc3+ qemu-0.11.0-13.fc12.x86_64 + libvirt 0.7.7.1

# virsh dump xxxx xxxx 
hangs.

In most case, I see following 2 back trace.(with gdb)

(gdb) bt

#0  ram_save_remaining () at /usr/src/debug/qemu-kvm-0.11.0/vl.c:3104
#1  ram_bytes_remaining () at /usr/src/debug/qemu-kvm-0.11.0/vl.c:3112
#2  0x00000000004ab2cf in do_info_migrate (mon=0x16b7970) at migration.c:150
#3  0x0000000000414b1a in monitor_handle_command (mon=<value optimized out>,

cmdline=<value optimized out>)
at /usr/src/debug/qemu-kvm-0.11.0/monitor.c:2870
#4 0x0000000000414c6a in monitor_command_cb (mon=0x16b7970,
cmdline=<value optimized out>, opaque=<value optimized out>) at /usr/src/debug/qemu-kvm-0.11.0/monitor.c:3160
#5 0x000000000048b71b in readline_handle_byte (rs=0x208d6a0,
ch=<value optimized out>) at readline.c:369
#6 0x0000000000414cdc in monitor_read (opaque=<value optimized out>,

    buf=0x7fff1b1104b0 "info migrate\r", size=13)
    at /usr/src/debug/qemu-kvm-0.11.0/monitor.c:3146
#7  0x00000000004b2a53 in tcp_chr_read (opaque=0x1614c30) at qemu-char.c:2006
#8  0x000000000040a6c7 in main_loop_wait (timeout=<value optimized out>)
    at /usr/src/debug/qemu-kvm-0.11.0/vl.c:4188

#9 0x000000000040eed5 in main_loop (argc=<value optimized out>,
argv=<value optimized out>, envp=<value optimized out>) at /usr/src/debug/qemu-kvm-0.11.0/vl.c:4414
#10 main (argc=<value optimized out>, argv=<value optimized out>,

    envp=<value optimized out>) at /usr/src/debug/qemu-kvm-0.11.0/vl.c:6263

(gdb) bt
#0 0x0000003c2680e0bd in write () at ../sysdeps/unix/syscall-template.S:82 #1 0x00000000004b304a in unix_write (fd=11, buf=<value optimized out>, len1=40)

    at qemu-char.c:512
#2  send_all (fd=11, buf=<value optimized out>, len1=40) at qemu-char.c:528
#3  0x0000000000411201 in monitor_flush (mon=0x16b7970)
    at /usr/src/debug/qemu-kvm-0.11.0/monitor.c:131
#4  0x0000000000414cdc in monitor_read (opaque=<value optimized out>,
    buf=0x7fff1b1104b0 "info migrate\r", size=13)
    at /usr/src/debug/qemu-kvm-0.11.0/monitor.c:3146
#5  0x00000000004b2a53 in tcp_chr_read (opaque=0x1614c30) at qemu-char.c:2006
#6  0x000000000040a6c7 in main_loop_wait (timeout=<value optimized out>)
    at /usr/src/debug/qemu-kvm-0.11.0/vl.c:4188

#7 0x000000000040eed5 in main_loop (argc=<value optimized out>,
argv=<value optimized out>, envp=<value optimized out>) at /usr/src/debug/qemu-kvm-0.11.0/vl.c:4414
#8 main (argc=<value optimized out>, argv=<value optimized out>,

    envp=<value optimized out>) at /usr/src/debug/qemu-kvm-0.11.0/vl.c:6263

And see no dump progress.

I'm sorry if this is not a hang but just verrrrry slow. I don't see any progress at lease for 15 minutes and qemu-kvm continues to use 75% of cpus. I'm not sure why "dump" command trigger migration code...

How long it takes to do "virsh dump xxx xxxx", an idle VM with 2G memory ? I'm sorry if I ask wrong mailing list.

Thanks,
-Kame