Re: [PATCH 0/3] virtio-net: inline header support

2012-10-03 Thread Rusty Russell
Anthony Liguori writes: > Rusty Russell writes: > >> "Michael S. Tsirkin" writes: >> >> There's a reason I haven't done this. I really, really dislike "my >> implemention isn't broken" feature bits. We could have an infinite >> number of them, for each bug in each device. >> >> So my plan was

Re: [PATCH 0/3] virtio-net: inline header support

2012-10-03 Thread Anthony Liguori
Rusty Russell writes: > Anthony Liguori writes: >> Rusty Russell writes: >> >>> "Michael S. Tsirkin" writes: >>> Thinking about Sasha's patches, we can reduce ring usage for virtio net small packets dramatically if we put virtio net header inline with the data. This can be

Re: [PATCH 0/3] virtio-net: inline header support

2012-10-03 Thread Rusty Russell
Anthony Liguori writes: > Rusty Russell writes: > >> "Michael S. Tsirkin" writes: >> >>> Thinking about Sasha's patches, we can reduce ring usage >>> for virtio net small packets dramatically if we put >>> virtio net header inline with the data. >>> This can be done for free in case guest net st

Re: [PATCH 0/3] virtio-net: inline header support

2012-10-03 Thread Anthony Liguori
Rusty Russell writes: > "Michael S. Tsirkin" writes: > > There's a reason I haven't done this. I really, really dislike "my > implemention isn't broken" feature bits. We could have an infinite > number of them, for each bug in each device. > > So my plan was to tie this assumption to the new P

Re: [PATCH 0/3] virtio-net: inline header support

2012-10-03 Thread Anthony Liguori
Rusty Russell writes: > "Michael S. Tsirkin" writes: > >> Thinking about Sasha's patches, we can reduce ring usage >> for virtio net small packets dramatically if we put >> virtio net header inline with the data. >> This can be done for free in case guest net stack allocated >> extra head room f

Re: [PATCH 0/3] virtio-net: inline header support

2012-10-03 Thread Rusty Russell
Paolo Bonzini writes: > Il 03/10/2012 08:44, Rusty Russell ha scritto: >> There's a reason I haven't done this. I really, really dislike "my >> implemention isn't broken" feature bits. We could have an infinite >> number of them, for each bug in each device. > > However, this bug affects (almos

Re: [PATCH 2/3] virtio-net: correct capacity math on ring full

2012-10-03 Thread Rusty Russell
"Michael S. Tsirkin" writes: > Capacity math on ring full is wrong: we are > looking at num_sg but that might be optimistic > because of indirect buffer use. > > The implementation also penalizes fast path > with extra memory accesses for the benefit of > ring full condition handling which is slow

Re: [PATCH 0/3] virtio-net: inline header support

2012-10-03 Thread Rusty Russell
Rusty Russell writes: > "Michael S. Tsirkin" writes: > >> Thinking about Sasha's patches, we can reduce ring usage >> for virtio net small packets dramatically if we put >> virtio net header inline with the data. >> This can be done for free in case guest net stack allocated >> extra head room f

Re: [PATCH 0/3] virtio-net: inline header support

2012-10-03 Thread Paolo Bonzini
Il 03/10/2012 08:44, Rusty Russell ha scritto: > There's a reason I haven't done this. I really, really dislike "my > implemention isn't broken" feature bits. We could have an infinite > number of them, for each bug in each device. However, this bug affects (almost) all implementations and (almo

Re: [PATCH 0/3] virtio-net: inline header support

2012-10-03 Thread Rusty Russell
"Michael S. Tsirkin" writes: > Thinking about Sasha's patches, we can reduce ring usage > for virtio net small packets dramatically if we put > virtio net header inline with the data. > This can be done for free in case guest net stack allocated > extra head room for the packet, and I don't see >