What is the status of jumbo frame support in dom0 and domU? Unless
something has changed I know it isn''t supported in domU, but
shouldn''t
it just work in dom0?
-Kip
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On 11 May 2005, at 01:14, Kip Macy wrote:> What is the status of jumbo frame support in dom0 and domU? Unless > something has changed I know it isn''t supported in domU, but shouldn''t > it just work in dom0?I think it''ll just work, but it''s untested. If the jumbo area spans multiple memory pages then it needs to be allocated with something like dma_alloc_coherent, or be represented by a fragmented skbuff. (i.e., hopefully the network stack and drivers don''t assume that kmalloc() always return physically contiguous memory extents). -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
On Wed, 11 May 2005, Keir Fraser wrote:> > On 11 May 2005, at 01:14, Kip Macy wrote: > > > What is the status of jumbo frame support in dom0 and domU? Unless > > something has changed I know it isn''t supported in domU, but shouldn''t > > it just work in dom0? > > I think it''ll just work, but it''s untested. If the jumbo area spans > multiple memory pages then it needs to be allocated with something like > dma_alloc_coherent, or be represented by a fragmented skbuff. (i.e., > hopefully the network stack and drivers don''t assume that kmalloc() > always return physically contiguous memory extents). >What all would need to change to support it for domUs? -Kip _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
On 11 May 2005, at 07:27, Kip Macy wrote:>>> What is the status of jumbo frame support in dom0 and domU? Unless >>> something has changed I know it isn''t supported in domU, but >>> shouldn''t >>> it just work in dom0? >> >> I think it''ll just work, but it''s untested. If the jumbo area spans >> multiple memory pages then it needs to be allocated with something >> like >> dma_alloc_coherent, or be represented by a fragmented skbuff. (i.e., >> hopefully the network stack and drivers don''t assume that kmalloc() >> always return physically contiguous memory extents). >> > > What all would need to change to support it for domUs?We need scatter-gather support on the device channel, and the frontend and backend both need to know how to queue and dequeue fragmented network buffers. -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
> > > > What all would need to change to support it for domUs? > > We need scatter-gather support on the device channel, and the frontend > and backend both need to know how to queue and dequeue fragmented > network buffers. > > -- KeirIs it anywhere on the roadmap? -Kip _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
> > > What all would need to change to support it for domUs? > > > > We need scatter-gather support on the device channel, and > the frontend > > and backend both need to know how to queue and dequeue fragmented > > network buffers. > > > > -- Keir > > Is it anywhere on the roadmap?Post 3.0. Having it working in dom0 is good enough for iSCSI. Unfortunately, many of the drivers use pci_map_page even for jumbo frames, which is defined as dma_map_page which uses page_to_phys and assumes that only a single page is being mapped. I think we''ll need to create another cache for jumbo frames and bless them with xen_contig_memory in the ctor function. Hmm, I''m not sure that ctor functions can return failure, though... Ian _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
On Wednesday 11 May 2005 01:21 am, Keir Fraser wrote:> On 11 May 2005, at 01:14, Kip Macy wrote: > > What is the status of jumbo frame support in dom0 and domU? Unless > > something has changed I know it isn''t supported in domU, but shouldn''t > > it just work in dom0? > > I think it''ll just work, but it''s untested. If the jumbo area spans > multiple memory pages then it needs to be allocated with something like > dma_alloc_coherent, or be represented by a fragmented skbuff. (i.e., > hopefully the network stack and drivers don''t assume that kmalloc() > always return physically contiguous memory extents).I''ve actually wanted to look into this for a while. It seems to me that MTUs of ~4000 (1 page) should be fairly trivial to impliment, and should boost performance significantly (with no extra cost as we are using the full page anyway). Kip, if you don''t want to do it, I will ;-) Thanks, Jon _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
> It seems to me that MTUs of ~4000 (1 page) should be fairly trivial to > impliment, and should boost performance significantly (with no extra cost as > we are using the full page anyway). > > Kip, if you don''t want to do it, I will ;-)That would be awesome. Let me know if you want some extra testing done for any patches. -Kip _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel