[libvirt-users] [libvirt] increase number of libvirt threads by starting tansient guest doamin - is it a bug?

Michal Privoznik mprivozn at redhat.com
Wed Oct 1 16:12:45 UTC 2014


On 01.10.2014 10:31, web2 wrote:
>   Hello,
>
> sorry for my later answer.
>
> so, after i started libvirtd (no vm´s running) and attach gdb i get the following threads
>
> (gdb) info thread
>   Id Target Id Frame
>   11 Thread 0x7f18fef4e700 (LWP 20695) "libvirtd" pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
>   10 Thread 0x7f18fe74d700 (LWP 20696) "libvirtd" pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
>   9 Thread 0x7f18fdf4c700 (LWP 20697) "libvirtd" pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
>   8 Thread 0x7f18fd74b700 (LWP 20698) "libvirtd" pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
>   7 Thread 0x7f18fcf4a700 (LWP 20699) "libvirtd" pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
>   6 Thread 0x7f18fc749700 (LWP 20700) "libvirtd" pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
>   5 Thread 0x7f18fbf48700 (LWP 20701) "libvirtd" pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
>   4 Thread 0x7f18fb747700 (LWP 20702) "libvirtd" pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
>   3 Thread 0x7f18faf46700 (LWP 20703) "libvirtd" pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
>   2 Thread 0x7f18fa745700 (LWP 20704) "libvirtd" pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
> * 1 Thread 0x7f190892f840 (LWP 20694) "libvirtd" 0x00007f190677d7cd in poll () at ../sysdeps/unix/syscall-template.S:81
>
> if i restore an persistent domain, i see the following in gdb:
>
> Detaching after fork from child process 20880.
> Detaching after fork from child process 20882.
> [New Thread 0x7f190893d700 (LWP 20883)]
> Detaching after fork from child process 20890.
> Detaching after fork from child process 20906.
>
> (gdb) info thread
>   Id Target Id Frame
>   12 Thread 0x7f190893d700 (LWP 20883) "libvirtd" 0x00007f1906e6684d in read () at ../sysdeps/unix/syscall-template.S:81
>   11 Thread 0x7f18fef4e700 (LWP 20695) "libvirtd" pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
>   10 Thread 0x7f18fe74d700 (LWP 20696) "libvirtd" pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
>   9 Thread 0x7f18fdf4c700 (LWP 20697) "libvirtd" pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
>   8 Thread 0x7f18fd74b700 (LWP 20698) "libvirtd" pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
>   7 Thread 0x7f18fcf4a700 (LWP 20699) "libvirtd" pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
>   6 Thread 0x7f18fc749700 (LWP 20700) "libvirtd" pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
>   5 Thread 0x7f18fbf48700 (LWP 20701) "libvirtd" pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
>   4 Thread 0x7f18fb747700 (LWP 20702) "libvirtd" pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
>   3 Thread 0x7f18faf46700 (LWP 20703) "libvirtd" pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
>   2 Thread 0x7f18fa745700 (LWP 20704) "libvirtd" pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
> * 1 Thread 0x7f190892f840 (LWP 20694) "libvirtd" 0x00007f190677d7cd in poll () at ../sysdeps/unix/syscall-template.S:81
>
> if i now destroy this vm i get the following:
>
>
> (gdb) info thread
>   Id Target Id Frame
>   12 Thread 0x7f190893d700 (LWP 20883) "libvirtd" 0x00007f1906e6684d in read () at ../sysdeps/unix/syscall-template.S:81
>   11 Thread 0x7f18fef4e700 (LWP 20695) "libvirtd" pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
>   10 Thread 0x7f18fe74d700 (LWP 20696) "libvirtd" pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
>   9 Thread 0x7f18fdf4c700 (LWP 20697) "libvirtd" pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
>   8 Thread 0x7f18fd74b700 (LWP 20698) "libvirtd" pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
>   7 Thread 0x7f18fcf4a700 (LWP 20699) "libvirtd" pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
>   6 Thread 0x7f18fc749700 (LWP 20700) "libvirtd" pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
>   5 Thread 0x7f18fbf48700 (LWP 20701) "libvirtd" pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
>   4 Thread 0x7f18fb747700 (LWP 20702) "libvirtd" pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
>   3 Thread 0x7f18faf46700 (LWP 20703) "libvirtd" pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
>   2 Thread 0x7f18fa745700 (LWP 20704) "libvirtd" pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
> * 1 Thread 0x7f190892f840 (LWP 20694) "libvirtd" 0x00007f190677d7cd in poll () at ../sysdeps/unix/syscall-template.S:81
>
> attaching thread Id 12 and bt:
> (gdb) thread 12
> [Switching to thread 12 (Thread 0x7f190893d700 (LWP 20883))]
> #0 0x00007f1906e6684d in read () at ../sysdeps/unix/syscall-template.S:81
> 81 T_PSEUDO (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS)
> (gdb) bt
> #0 0x00007f1906e6684d in read () at ../sysdeps/unix/syscall-template.S:81
> #1 0x00007f18f8c415be in read (__nbytes=16, __buf=0x7f18d4000c50, __fd=26) at /usr/include/bits/unistd.h:44
> #2 read_all (fd=26, data=data at entry =0x7f18d4000c50, len=len at entry =16, nonblocking=nonblocking at entry =0) at xs.c:374
> #3 0x00007f18f8c41675 in read_message (h=h at entry =0x7f18e8001070, nonblocking=nonblocking at entry =0) at xs.c:1139
> #4 0x00007f18f8c41e90 in read_thread (arg=0x7f18e8001070) at xs.c:1211
> #5 0x00007f1906e5ff35 in start_thread (arg=0x7f190893d700) at pthread_create.c:309
> #6 0x00007f1906787c3d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111
>
> and then bt full:
>
> (gdb) bt full
> #0 0x00007f1906e6684d in read () at ../sysdeps/unix/syscall-template.S:81
> No locals.
> #1 0x00007f18f8c415be in read (__nbytes=16, __buf=0x7f18d4000c50, __fd=26) at /usr/include/bits/unistd.h:44
> No locals.
> #2 read_all (fd=26, data=data at entry =0x7f18d4000c50, len=len at entry =16, nonblocking=nonblocking at entry =0) at xs.c:374
>   done = <optimized out>
> #3 0x00007f18f8c41675 in read_message (h=h at entry =0x7f18e8001070, nonblocking=nonblocking at entry =0) at xs.c:1139
>   __clframe = {__cancel_routine = <optimized out>, __cancel_arg = 0x7f18d4000c40, __do_it = 1, __cancel_type = <optimized out>}
>   msg = 0x7f18d4000c40
>   body = 0x0
>   saved_errno = 0
>   ret = -1
> #4 0x00007f18f8c41e90 in read_thread (arg=0x7f18e8001070) at xs.c:1211
>   h = 0x7f18e8001070
>   fd = <optimized out>

This stack doesn't come from libvirt. I suspect it comes from a library 
that libvirtd is linked with. Maybe libxl? What's the connection uri 
you're using?

> #5 0x00007f1906e5ff35 in start_thread (arg=0x7f190893d700) at pthread_create.c:309
>   __res = <optimized out>
>   pd = 0x7f190893d700
>   now = <optimized out>
>   unwind_buf = {cancel_jmp_buf = {{jmp_buf = {139745494816512, 9092725460686644452, 1, 0, 139745494817216, 139745494816512, -9214988784542636828, -9214975709026802460}, mask_was_saved = 0}}, priv = {pad = {0x0, 0x0, 0x0, 0x0},
>   data = {prev = 0x0, cleanup = 0x0, canceltype = 0}}}
>   not_first_call = <optimized out>
>   pagesize_m1 = <optimized out>
>   sp = <optimized out>
>   freesize = <optimized out>
> #6 0x00007f1906787c3d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111
> No locals.


Michal




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