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Description of problem:
The system won't bypass the cache even enable the auto_dump_bypass_cache in qemu.conf. This problem does not exist on x86.
Version-Release number of selected component (if applicable):
libvirt-1.2.17-1.el7.ppc64le
qemu-kvm-rhev-2.3.0-5.el7.ppc64le
kernel-3.10.0-282.el7.ppc64le
How reproducible:
100%
Steps to Reproduce:
1. Set auto_dump_bypass_cache = 1 in qemu.conf
# cat /etc/libvirt/qemu.conf
...
auto_dump_bypass_cache = 1
...
2. Restart libvirtd, # systemctl restart libvirtd
3. Edit XML with <on_crash>coredump-restart</on_crash>
4. Start guest.
5. Prepare command line on another terminal-2 with below command.
# cat /proc/$(lsof -w /var/lib/libvirt/qemu/dump/*|awk '/libvirt_i/{print $2}')/fdinfo/*1*
6. Within the guest, stop kdump service and make the guest crash.
# systemctl stop kdump
# echo c > /proc/sysrq-trigger
7. Before the guest finishes crashing, run the command on step 5 for many times on terminal-2
# cat /proc/$(lsof -w /var/lib/libvirt/qemu/dump/*|awk '/libvirt_i/{print $2}')/fdinfo/*1*
pos: 3822059520
flags: 0600001
...
pos: 3968860160
flags: 0600001
...
pos: 4107272192
flags: 0600001
Actual result:
In the flags in step 6 output, the third value is '0' which stands for 'auto_dump_bypass_cache' is disabled. The system did not bypass the cache for auto dump with auto_dump_bypass_cache enabled.
Expect result:
In the flags in step 6 output, the third value is '4' which stands for 'auto_dump_bypass_cache' is enabled. The system should bypass the cache for auto dump with auto_dump_bypass_cache enabled.
(In reply to Dan Zheng from comment #0)
[...]
> # cat /proc/$(lsof -w /var/lib/libvirt/qemu/dump/*|awk '/libvirt_i/{print
> $2}')/fdinfo/*1*
> pos: 3822059520
> flags: 0600001
> ...
> pos: 3968860160
> flags: 0600001
> ...
> pos: 4107272192
> flags: 0600001
>
> Actual result:
> In the flags in step 6 output, the third value is '0' which stands for
> 'auto_dump_bypass_cache' is disabled. The system did not bypass the cache
> for auto dump with auto_dump_bypass_cache enabled.
>
> Expect result:
> In the flags in step 6 output, the third value is '4' which stands for
> 'auto_dump_bypass_cache' is enabled. The system should bypass the cache for
> auto dump with auto_dump_bypass_cache enabled.
The testing methodology is not entirely correct because it
doesn't account for the fact that the concrete value for eg.
O_DIRECT can be different depending on the architecture.
I've attached a simple C program that demostrates the issue:
when run on an x86_64 host, it will print
$ ./direct whatever
Without O_DIRECT:
pos: 0
flags: 0100001
mnt_id: 62
With O_DIRECT:
pos: 0
flags: 0140001
mnt_id: 62
whereas on a ppc64le or aarch64 host it will print
$ ./direct whatever
Without O_DIRECT:
pos: 0
flags: 0400001
mnt_id: 80
With O_DIRECT:
pos: 0
flags: 0600001
mnt_id: 80
So 0600001 is the expected output for ppc64le hosts, and
libvirt is behaving correctly. Closing as NOTABUG.
Description of problem: The system won't bypass the cache even enable the auto_dump_bypass_cache in qemu.conf. This problem does not exist on x86. Version-Release number of selected component (if applicable): libvirt-1.2.17-1.el7.ppc64le qemu-kvm-rhev-2.3.0-5.el7.ppc64le kernel-3.10.0-282.el7.ppc64le How reproducible: 100% Steps to Reproduce: 1. Set auto_dump_bypass_cache = 1 in qemu.conf # cat /etc/libvirt/qemu.conf ... auto_dump_bypass_cache = 1 ... 2. Restart libvirtd, # systemctl restart libvirtd 3. Edit XML with <on_crash>coredump-restart</on_crash> 4. Start guest. 5. Prepare command line on another terminal-2 with below command. # cat /proc/$(lsof -w /var/lib/libvirt/qemu/dump/*|awk '/libvirt_i/{print $2}')/fdinfo/*1* 6. Within the guest, stop kdump service and make the guest crash. # systemctl stop kdump # echo c > /proc/sysrq-trigger 7. Before the guest finishes crashing, run the command on step 5 for many times on terminal-2 # cat /proc/$(lsof -w /var/lib/libvirt/qemu/dump/*|awk '/libvirt_i/{print $2}')/fdinfo/*1* pos: 3822059520 flags: 0600001 ... pos: 3968860160 flags: 0600001 ... pos: 4107272192 flags: 0600001 Actual result: In the flags in step 6 output, the third value is '0' which stands for 'auto_dump_bypass_cache' is disabled. The system did not bypass the cache for auto dump with auto_dump_bypass_cache enabled. Expect result: In the flags in step 6 output, the third value is '4' which stands for 'auto_dump_bypass_cache' is enabled. The system should bypass the cache for auto dump with auto_dump_bypass_cache enabled.