[PATCH 0/2] qemu: Set noqueue qdisc for TAP devices

[Daniel Henrique Barboza]

On 10/13/20 11:06 AM, Michal Privoznik wrote:
> On 10/13/20 3:09 PM, Daniel Henrique Barboza wrote:
>>
>>
>> On 10/8/20 3:10 PM, Michal Privoznik wrote:
>>> See 2/2 for detailed explanation.
>>> Long story short - we can squeeze more bandwidth from TAP devices we
>>> create for domains.
>>>
>>> Michal Prívozník (2):
>>>    virnetdev: Introduce virNetDevSetRootQDisc()
>>>    qemu: Set noqueue qdisc for TAP devices
>>
>>
>> Reviewed-by: Daniel Henrique Barboza <danielhb413 at gmail.com>
>>
> 
> Thanks. Just before I merged these I realized that it will be a good idea to mock virNetDevSetRootQDisc() so that we don't run tc from the test suite. But the diff is really trivial:
> 
> diff --git i/src/util/virnetdev.h w/src/util/virnetdev.h
> index 82943b8e08..dfef49938f 100644
> --- i/src/util/virnetdev.h
> +++ w/src/util/virnetdev.h
> @@ -313,6 +313,7 @@ int virNetDevRunEthernetScript(const char *ifname, const char *script)
>       G_GNUC_NO_INLINE;
> 
>   int virNetDevSetRootQDisc(const char *ifname,
> -                          const char *qdisc);
> +                          const char *qdisc)
> +    G_GNUC_NO_INLINE;
> 
>   G_DEFINE_AUTOPTR_CLEANUP_FUNC(virNetDevRxFilter, virNetDevRxFilterFree);
> diff --git i/tests/qemuxml2argvmock.c w/tests/qemuxml2argvmock.c
> index 9bf4357b66..b9322f4f2a 100644
> --- i/tests/qemuxml2argvmock.c
> +++ w/tests/qemuxml2argvmock.c
> @@ -286,3 +286,11 @@ qemuBuildTPMOpenBackendFDs(const char *tpmdev G_GNUC_UNUSED,
>       *cancelfd = 1731;
>       return 0;
>   }
> +
> +
> +int
> +virNetDevSetRootQDisc(const char *ifname G_GNUC_UNUSED,
> +                      const char *qdisc G_GNUC_UNUSED)
> +{
> +    return 0;
> +}
> 
> 
> Hopefully, you are okay if I squash this to 2/2.


Yep, go ahead.


> 
>>
>> Have you tried it out with older kernels? Reading the bug I understood
>> that 4.2 and older (2015 kernels) does not have qdisc support and that you
>> can, for example, test for NETIF_F_LLTX of the ETHTOOL_GFEATURES ioctl to
>> verify it.
>>
> 
> I didn't, but I had this on mind when writing patches and I made the whole thing best effort. Note that qemuDomainInterfaceSetDefaultQDisc() retval is not checked for => if setting noqueue fails (for whatever reason) then worst case scenario an error is printed into logs.
> 
>> I consider this to be a 'nice to have' that can be added in a follow up
>> patch though, if applicable. By the way, do we have any documentation about
>> "the latest Libvirt release will not care about N+ years old kernel/QEMU"?
> 
> I'm not sure what you mean. This perhaps?
> 
> https://libvirt.org/platforms.html#linux-freebsd-and-macos


Thanks, this is what I was looking for.



DHB


> 
> Michal
>