a ping on this one;
this change makes sense to me, and makes performance better in specific cases, by avoiding --bypass-cache before reaching the "cache trashing" state.
However, before virsh save was guarenteed to go through iohelper, now it is not.
The iohelper was guaranteeing a virFileDataSync before exiting,
while after the change the data will still be in-flight between the kernel and the device as virsh save returns to the prompt.
Seems more efficient, but wanted to mention this as a user-visible change.
Thoughts?
Claudio
On 4/13/22 9:18 AM, Ani Sinha wrote:
> On Tue, Apr 12, 2022 at 2:48 PM Claudio Fontana <cfontana@xxxxxxx> wrote:
>>
>> align the "save" with the "restore" code,
>> by only using the wrapper when using --bypass-cache.
>>
>> This avoids a copy, resulting in better performance.
>>
>> Signed-off-by: Claudio Fontana <cfontana@xxxxxxx>
>
> Reviewed-by: Ani Sinha <ani@xxxxxxxxxxx>
>
>> ---
>> src/qemu/qemu_saveimage.c | 6 ++++--
>> 1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/src/qemu/qemu_saveimage.c b/src/qemu/qemu_saveimage.c
>> index 4fd4c5cfcd..5ea1b2fbcc 100644
>> --- a/src/qemu/qemu_saveimage.c
>> +++ b/src/qemu/qemu_saveimage.c
>> @@ -289,8 +289,10 @@ qemuSaveImageCreate(virQEMUDriver *driver,
>> if (qemuSecuritySetImageFDLabel(driver->securityManager, vm->def, fd) < 0)
>> goto cleanup;
>>
>> - if (!(wrapperFd = virFileWrapperFdNew(&fd, path, wrapperFlags)))
>> - goto cleanup;
>> + if ((flags & VIR_DOMAIN_SAVE_BYPASS_CACHE)) {
>> + if (!(wrapperFd = virFileWrapperFdNew(&fd, path, wrapperFlags)))
>> + goto cleanup;
>> + }
>>
>> if (virQEMUSaveDataWrite(data, fd, path) < 0)
>> goto cleanup;
>> --
>> 2.34.1
>>
>
