| Message ID | 511DF166.2070105@dlhnet.de |
|---|---|
| State | New |
| Headers | show |
On Fri, Feb 15, 2013 at 09:27:18AM +0100, Peter Lieven wrote: > historically the kernel queues packets two times. once > at the device and second in qdisc. this is believed to cause > interface stalls if one of these queues overruns. > > setting IFF_ONE_QUEUE is the default in kernels >= 3.8. the > flag is ignored since then. see kernel commit > 5d097109257c03a71845729f8db6b5770c4bbedc > > Signed-off-by: Peter Lieven <pl@kamp.de> > --- > net/tap-linux.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Am 15.02.2013 um 10:16 schrieb Stefan Hajnoczi <stefanha@gmail.com>: > On Fri, Feb 15, 2013 at 09:27:18AM +0100, Peter Lieven wrote: >> historically the kernel queues packets two times. once >> at the device and second in qdisc. this is believed to cause >> interface stalls if one of these queues overruns. >> >> setting IFF_ONE_QUEUE is the default in kernels >= 3.8. the >> flag is ignored since then. see kernel commit >> 5d097109257c03a71845729f8db6b5770c4bbedc >> >> Signed-off-by: Peter Lieven <pl@kamp.de> >> --- >> net/tap-linux.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) > > Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> it seems that IFF_ONE_QUEUE is not defined in qemu headers. i will sent an update. sorry, peter
On 15/02/13 09:27, Peter Lieven wrote: > historically the kernel queues packets two times. once > at the device and second in qdisc. this is believed to cause > interface stalls if one of these queues overruns. > > setting IFF_ONE_QUEUE is the default in kernels >= 3.8. the > flag is ignored since then. see kernel commit > 5d097109257c03a71845729f8db6b5770c4bbedc > > Signed-off-by: Peter Lieven <pl@kamp.de> > --- > net/tap-linux.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/net/tap-linux.c b/net/tap-linux.c > index a953189..2759b78 100644 > --- a/net/tap-linux.c > +++ b/net/tap-linux.c > @@ -49,7 +49,7 @@ int tap_open(char *ifname, int ifname_size, int *vnet_hdr, > return -1; > } > memset(&ifr, 0, sizeof(ifr)); > - ifr.ifr_flags = IFF_TAP | IFF_NO_PI; > + ifr.ifr_flags = IFF_TAP | IFF_NO_PI | IFF_ONE_QUEUE; > > if (*vnet_hdr) { > unsigned int features; Wouldn't that break macvtap? there is case TUNSETIFF: /* ignore the name, just look at flags */ if (get_user(u, &ifr->ifr_flags)) return -EFAULT; ret = 0; if ((u & ~IFF_VNET_HDR) != (IFF_NO_PI | IFF_TAP)) ret = -EINVAL; in drivers/net/macvtap.c
Am 15.02.2013 um 10:22 schrieb Christian Borntraeger <borntraeger@de.ibm.com>: > On 15/02/13 09:27, Peter Lieven wrote: >> historically the kernel queues packets two times. once >> at the device and second in qdisc. this is believed to cause >> interface stalls if one of these queues overruns. >> >> setting IFF_ONE_QUEUE is the default in kernels >= 3.8. the >> flag is ignored since then. see kernel commit >> 5d097109257c03a71845729f8db6b5770c4bbedc >> >> Signed-off-by: Peter Lieven <pl@kamp.de> >> --- >> net/tap-linux.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/net/tap-linux.c b/net/tap-linux.c >> index a953189..2759b78 100644 >> --- a/net/tap-linux.c >> +++ b/net/tap-linux.c >> @@ -49,7 +49,7 @@ int tap_open(char *ifname, int ifname_size, int *vnet_hdr, >> return -1; >> } >> memset(&ifr, 0, sizeof(ifr)); >> - ifr.ifr_flags = IFF_TAP | IFF_NO_PI; >> + ifr.ifr_flags = IFF_TAP | IFF_NO_PI | IFF_ONE_QUEUE; >> >> if (*vnet_hdr) { >> unsigned int features; > > Wouldn't that break macvtap? > > there is > > case TUNSETIFF: > /* ignore the name, just look at flags */ > if (get_user(u, &ifr->ifr_flags)) > return -EFAULT; > > ret = 0; > if ((u & ~IFF_VNET_HDR) != (IFF_NO_PI | IFF_TAP)) > ret = -EINVAL; > > > in drivers/net/macvtap.c > > wasn`t aware I will modify this to only be set on linux Peter
On 15/02/13 10:25, Peter Lieven wrote: > > Am 15.02.2013 um 10:22 schrieb Christian Borntraeger <borntraeger@de.ibm.com>: > >> On 15/02/13 09:27, Peter Lieven wrote: >>> historically the kernel queues packets two times. once >>> at the device and second in qdisc. this is believed to cause >>> interface stalls if one of these queues overruns. >>> >>> setting IFF_ONE_QUEUE is the default in kernels >= 3.8. the >>> flag is ignored since then. see kernel commit >>> 5d097109257c03a71845729f8db6b5770c4bbedc >>> >>> Signed-off-by: Peter Lieven <pl@kamp.de> >>> --- >>> net/tap-linux.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/net/tap-linux.c b/net/tap-linux.c >>> index a953189..2759b78 100644 >>> --- a/net/tap-linux.c >>> +++ b/net/tap-linux.c >>> @@ -49,7 +49,7 @@ int tap_open(char *ifname, int ifname_size, int *vnet_hdr, >>> return -1; >>> } >>> memset(&ifr, 0, sizeof(ifr)); >>> - ifr.ifr_flags = IFF_TAP | IFF_NO_PI; >>> + ifr.ifr_flags = IFF_TAP | IFF_NO_PI | IFF_ONE_QUEUE; >>> >>> if (*vnet_hdr) { >>> unsigned int features; >> >> Wouldn't that break macvtap? >> >> there is >> >> case TUNSETIFF: >> /* ignore the name, just look at flags */ >> if (get_user(u, &ifr->ifr_flags)) >> return -EFAULT; >> >> ret = 0; >> if ((u & ~IFF_VNET_HDR) != (IFF_NO_PI | IFF_TAP)) >> ret = -EINVAL; >> >> >> in drivers/net/macvtap.c >> >> > > wasn`t aware I will modify this to only be set on linux > > Peter macvtap is a Linux driver. It is given to qemu usually via libvirt with something like -netdev tap,fd=21,id=hostnet0,vhost=on,vhostfd=22 and then having fd21 pointing to an open /dev/tap... device which is backed by macvtap. Christian
diff --git a/net/tap-linux.c b/net/tap-linux.c index a953189..2759b78 100644 --- a/net/tap-linux.c +++ b/net/tap-linux.c @@ -49,7 +49,7 @@ int tap_open(char *ifname, int ifname_size, int *vnet_hdr, return -1; } memset(&ifr, 0, sizeof(ifr)); - ifr.ifr_flags = IFF_TAP | IFF_NO_PI; + ifr.ifr_flags = IFF_TAP | IFF_NO_PI | IFF_ONE_QUEUE; if (*vnet_hdr) { unsigned int features;
historically the kernel queues packets two times. once at the device and second in qdisc. this is believed to cause interface stalls if one of these queues overruns. setting IFF_ONE_QUEUE is the default in kernels >= 3.8. the flag is ignored since then. see kernel commit 5d097109257c03a71845729f8db6b5770c4bbedc Signed-off-by: Peter Lieven <pl@kamp.de> --- net/tap-linux.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)