Hi guys:
env: [root@cloudf ~]# uname -a Linux cloudf.fedora.com 3.18.7-100.fc20.x86_64 #1 SMP Wed Feb 11 19:01:50 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux [root@cloudf ~]# rpm -q qemu-kvm qemu-kvm-1.6.2-13.fc20.x86_64
I found there is a "futex" thead after creating a kvm guest by the command:"/usr/bin/qemu-system-x86_64 -machine accel=kvm -hda /opt/todaygoods_SLES_11_SP3_JeOS.x86_64-0.0.2.raw -vnc 192.168.0.110:6"
root@cloudf task]# ps aux | grep qemu root 13111 0.3 2.8 546760 227340 pts/3 S+ 18:26 0:12 gdb qemu-system-x86_64 root 14379 85.2 2.0 699004 165496 pts/3 tl 18:49 31:12 /usr/bin/qemu-system-x86_64 -machine accel=kvm -hda /opt/todaygoods_SLES_11_SP3_JeOS.x86_64-0.0.2.raw -vnc 192.168.0.110:6
the process 14379 has three threads, I'm familiar with the two of them except the third thread (lwp :14418)
[root@cloudf 14379]# cd /proc/14379/ [root@cloudf 14379]# cat task/14 14379/ 14416/ 14418/ [root@cloudf 14379]# cat task/14379/stack [<ffffffff8121d1e9>] poll_schedule_timeout+0x49/0x70 [<ffffffff8121e8e4>] do_sys_poll+0x484/0x5c0 [<ffffffff8121eb24>] SyS_poll+0x74/0x110 [<ffffffff8174cfa9>] system_call_fastpath+0x12/0x17 [<ffffffffffffffff>] 0xffffffffffffffff [root@cloudf 14379]# cat task/14416/stack [<ffffffffa05cf92d>] kvm_arch_vcpu_ioctl_run+0xb0d/0x1280 [kvm] [<ffffffffa05b7bb2>] kvm_vcpu_ioctl+0x292/0x5c0 [kvm] [<ffffffff8121c710>] do_vfs_ioctl+0x2e0/0x4a0 [<ffffffff8121c951>] SyS_ioctl+0x81/0xa0 [<ffffffff8174cfa9>] system_call_fastpath+0x12/0x17 [<ffffffffffffffff>] 0xffffffffffffffff [root@cloudf 14379]# cat task/14418/stack [<ffffffff8110b6e0>] futex_wait_queue_me+0xd0/0x130 [<ffffffff8110b9e6>] futex_wait+0x176/0x270 [<ffffffff8110dc7e>] do_futex+0x10e/0xac0 [<ffffffff8110e6b0>] SyS_futex+0x80/0x180 [<ffffffff8174cfa9>] system_call_fastpath+0x12/0x17 [<ffffffffffffffff>] 0xffffffffffffffff
what's the "futex" thread doing when create a kvm guest ? I deeped into the qemu code , but I failed to find where call "futex" system call.
can you help me ?
On Sun, Feb 22, 2015 at 1:36 PM, Hu Jun jhu_com@163.com wrote:
Hi guys:
env: [root@cloudf ~]# uname -a Linux cloudf.fedora.com 3.18.7-100.fc20.x86_64 #1 SMP Wed Feb 11 19:01:50 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux [root@cloudf ~]# rpm -q qemu-kvm qemu-kvm-1.6.2-13.fc20.x86_64
I found there is a "futex" thead after creating a kvm guest by the command:"/usr/bin/qemu-system-x86_64 -machine accel=kvm -hda /opt/todaygoods_SLES_11_SP3_JeOS.x86_64-0.0.2.raw -vnc 192.168.0.110:6"
root@cloudf task]# ps aux | grep qemu root 13111 0.3 2.8 546760 227340 pts/3 S+ 18:26 0:12 gdb qemu-system-x86_64 root 14379 85.2 2.0 699004 165496 pts/3 tl 18:49 31:12 /usr/bin/qemu-system-x86_64 -machine accel=kvm -hda /opt/todaygoods_SLES_11_SP3_JeOS.x86_64-0.0.2.raw -vnc 192.168.0.110:6
the process 14379 has three threads, I'm familiar with the two of them except the third thread (lwp :14418)
[root@cloudf 14379]# cd /proc/14379/ [root@cloudf 14379]# cat task/14 14379/ 14416/ 14418/ [root@cloudf 14379]# cat task/14379/stack [<ffffffff8121d1e9>] poll_schedule_timeout+0x49/0x70 [<ffffffff8121e8e4>] do_sys_poll+0x484/0x5c0 [<ffffffff8121eb24>] SyS_poll+0x74/0x110 [<ffffffff8174cfa9>] system_call_fastpath+0x12/0x17 [<ffffffffffffffff>] 0xffffffffffffffff [root@cloudf 14379]# cat task/14416/stack [<ffffffffa05cf92d>] kvm_arch_vcpu_ioctl_run+0xb0d/0x1280 [kvm] [<ffffffffa05b7bb2>] kvm_vcpu_ioctl+0x292/0x5c0 [kvm] [<ffffffff8121c710>] do_vfs_ioctl+0x2e0/0x4a0 [<ffffffff8121c951>] SyS_ioctl+0x81/0xa0 [<ffffffff8174cfa9>] system_call_fastpath+0x12/0x17 [<ffffffffffffffff>] 0xffffffffffffffff [root@cloudf 14379]# cat task/14418/stack [<ffffffff8110b6e0>] futex_wait_queue_me+0xd0/0x130 [<ffffffff8110b9e6>] futex_wait+0x176/0x270 [<ffffffff8110dc7e>] do_futex+0x10e/0xac0 [<ffffffff8110e6b0>] SyS_futex+0x80/0x180 [<ffffffff8174cfa9>] system_call_fastpath+0x12/0x17 [<ffffffffffffffff>] 0xffffffffffffffff
what's the "futex" thread doing when create a kvm guest ? I deeped into the qemu code , but I failed to find where call "futex" system call.
It is unlikely that you will find any call to "futex" in the source code of an application. It doesn't even have glibc interface. Most of the time it is an implementation detail for something else. For instance pthread_join is implemented using the futex system call.
But the question here is ... what is the problem that you are trying to solve?
thank you for reminding me. /proc/$PID/stack shows the function call stack in kernel space, but yesterday I thought it shows stack in user space.
I only want to understand what's the thread doing , not for a specific issue.
On 02/23/2015 06:17 AM, drago01 wrote:
On Sun, Feb 22, 2015 at 1:36 PM, Hu Jun jhu_com@163.com wrote:
Hi guys:
env: [root@cloudf ~]# uname -a Linux cloudf.fedora.com 3.18.7-100.fc20.x86_64 #1 SMP Wed Feb 11 19:01:50 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux [root@cloudf ~]# rpm -q qemu-kvm qemu-kvm-1.6.2-13.fc20.x86_64
I found there is a "futex" thead after creating a kvm guest by the command:"/usr/bin/qemu-system-x86_64 -machine accel=kvm -hda /opt/todaygoods_SLES_11_SP3_JeOS.x86_64-0.0.2.raw -vnc 192.168.0.110:6"
root@cloudf task]# ps aux | grep qemu root 13111 0.3 2.8 546760 227340 pts/3 S+ 18:26 0:12 gdb qemu-system-x86_64 root 14379 85.2 2.0 699004 165496 pts/3 tl 18:49 31:12 /usr/bin/qemu-system-x86_64 -machine accel=kvm -hda /opt/todaygoods_SLES_11_SP3_JeOS.x86_64-0.0.2.raw -vnc 192.168.0.110:6
the process 14379 has three threads, I'm familiar with the two of them except the third thread (lwp :14418)
[root@cloudf 14379]# cd /proc/14379/ [root@cloudf 14379]# cat task/14 14379/ 14416/ 14418/ [root@cloudf 14379]# cat task/14379/stack [<ffffffff8121d1e9>] poll_schedule_timeout+0x49/0x70 [<ffffffff8121e8e4>] do_sys_poll+0x484/0x5c0 [<ffffffff8121eb24>] SyS_poll+0x74/0x110 [<ffffffff8174cfa9>] system_call_fastpath+0x12/0x17 [<ffffffffffffffff>] 0xffffffffffffffff [root@cloudf 14379]# cat task/14416/stack [<ffffffffa05cf92d>] kvm_arch_vcpu_ioctl_run+0xb0d/0x1280 [kvm] [<ffffffffa05b7bb2>] kvm_vcpu_ioctl+0x292/0x5c0 [kvm] [<ffffffff8121c710>] do_vfs_ioctl+0x2e0/0x4a0 [<ffffffff8121c951>] SyS_ioctl+0x81/0xa0 [<ffffffff8174cfa9>] system_call_fastpath+0x12/0x17 [<ffffffffffffffff>] 0xffffffffffffffff [root@cloudf 14379]# cat task/14418/stack [<ffffffff8110b6e0>] futex_wait_queue_me+0xd0/0x130 [<ffffffff8110b9e6>] futex_wait+0x176/0x270 [<ffffffff8110dc7e>] do_futex+0x10e/0xac0 [<ffffffff8110e6b0>] SyS_futex+0x80/0x180 [<ffffffff8174cfa9>] system_call_fastpath+0x12/0x17 [<ffffffffffffffff>] 0xffffffffffffffff
what's the "futex" thread doing when create a kvm guest ? I deeped into the qemu code , but I failed to find where call "futex" system call.
It is unlikely that you will find any call to "futex" in the source code of an application. It doesn't even have glibc interface. Most of the time it is an implementation detail for something else. For instance pthread_join is implemented using the futex system call.
But the question here is ... what is the problem that you are trying to solve?
On (Sun) 22 Feb 2015 [20:36:24], Hu Jun wrote:
Hi guys:
env: [root@cloudf ~]# uname -a Linux cloudf.fedora.com 3.18.7-100.fc20.x86_64 #1 SMP Wed Feb 11 19:01:50 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux [root@cloudf ~]# rpm -q qemu-kvm qemu-kvm-1.6.2-13.fc20.x86_64
I found there is a "futex" thead after creating a kvm guest by the command:"/usr/bin/qemu-system-x86_64 -machine accel=kvm -hda /opt/todaygoods_SLES_11_SP3_JeOS.x86_64-0.0.2.raw -vnc 192.168.0.110:6"
root@cloudf task]# ps aux | grep qemu root 13111 0.3 2.8 546760 227340 pts/3 S+ 18:26 0:12 gdb qemu-system-x86_64 root 14379 85.2 2.0 699004 165496 pts/3 tl 18:49 31:12 /usr/bin/qemu-system-x86_64 -machine accel=kvm -hda /opt/todaygoods_SLES_11_SP3_JeOS.x86_64-0.0.2.raw -vnc 192.168.0.110:6
the process 14379 has three threads, I'm familiar with the two of them except the third thread (lwp :14418)
[root@cloudf 14379]# cd /proc/14379/ [root@cloudf 14379]# cat task/14 14379/ 14416/ 14418/ [root@cloudf 14379]# cat task/14379/stack [<ffffffff8121d1e9>] poll_schedule_timeout+0x49/0x70 [<ffffffff8121e8e4>] do_sys_poll+0x484/0x5c0
so this is the main loop thread
[<ffffffff8121eb24>] SyS_poll+0x74/0x110 [<ffffffff8174cfa9>] system_call_fastpath+0x12/0x17 [<ffffffffffffffff>] 0xffffffffffffffff [root@cloudf 14379]# cat task/14416/stack [<ffffffffa05cf92d>] kvm_arch_vcpu_ioctl_run+0xb0d/0x1280 [kvm] [<ffffffffa05b7bb2>] kvm_vcpu_ioctl+0x292/0x5c0 [kvm]
this is the guest vcpu thread
[<ffffffff8121c710>] do_vfs_ioctl+0x2e0/0x4a0 [<ffffffff8121c951>] SyS_ioctl+0x81/0xa0 [<ffffffff8174cfa9>] system_call_fastpath+0x12/0x17 [<ffffffffffffffff>] 0xffffffffffffffff [root@cloudf 14379]# cat task/14418/stack [<ffffffff8110b6e0>] futex_wait_queue_me+0xd0/0x130 [<ffffffff8110b9e6>] futex_wait+0x176/0x270 [<ffffffff8110dc7e>] do_futex+0x10e/0xac0
and this must be some thread -- like network or block, depending on your qemu config. The futex is via pthreads, so just looking at the qemu code based on what config you're using will get you the answer.
[<ffffffff8110e6b0>] SyS_futex+0x80/0x180 [<ffffffff8174cfa9>] system_call_fastpath+0x12/0x17 [<ffffffffffffffff>] 0xffffffffffffffff
what's the "futex" thread doing when create a kvm guest ? I deeped into the qemu code , but I failed to find where call "futex" system call.
can you help me ?
Anyway this is not relevant to the fedora kernel, you'll have more luck on the qemu list or the fedora virt list.
Amit
kernel@lists.fedoraproject.org
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Amit Shah -
drago01 -
Hu Jun