[PATCH 0/2] qemu: Set noqueue qdisc for TAP devices
Daniel Henrique Barboza
danielhb413 at gmail.com
Tue Oct 13 14:13:13 UTC 2020
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)
> 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;
> +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?
Thanks, this is what I was looking for.
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