On Thu, Dec 08, 2011 at 12:49:18PM -0500, John Baldwin wrote:
> On 12/5/11 2:31 PM, Luigi Rizzo wrote:
> >On Mon, Dec 05, 2011 at 07:38:54PM +0100, Marius Strobl wrote:
> >>On Mon, Dec 05, 2011 at 03:33:14PM +0000, Luigi Rizzo wrote:
> >...
> >>>+#ifdef DEV_NETMAP
> >>>+ if (slot) {
> >>>+ int si = i + na->tx_rings[txr->me].nkr_hwofs;
> >>>+ void *addr;
> >>>+
> >>>+ if (si>= na->num_tx_desc)
> >>>+ si -= na->num_tx_desc;
> >>>+ addr = NMB(slot + si);
> >>>+ txr->tx_base[i].buffer_addr =
> >>>+ htole64(vtophys(addr));
> >>>+ /* reload the map for netmap mode */
> >>>+ netmap_load_map(txr->txtag,
> >>>+ txbuf->map, addr, na->buff_size);
> >>>+ }
> >>>+#endif /* DEV_NETMAP */
> >>
> >>Can these vtophys(9) usages be fixed to use bus_dma(9) instead so netmap
> >>works with bounce buffers, IOMMUs etc?
> >
> >maybe. Can you suggest how to change it ?
> >
> >Consider that (not here but in other places) vtophys() is called
> >in a time-critical loop so performance matters a lot. As long as i
> >can compute the physical address in advance and cache it in my own
> >array, i suppose that should be fine (in which case the calls to
> >vtophys(addr) would become NMPB(slot + si) where the NMPB() macro
> >would hide translations and checks.
>
> For your use case, you probably don't want to be coping with bounce
> buffers at all. That is, if you are preallocating long-lived buffers
> that keep getting reused while netmap is active that are allocated at
> startup and free'd at teardown, you probably want to allocate buffers
> that won't require bounce buffers. That means you have to let the
> drivers allocate the buffers (or give you a suitable bus_dma tag since
> different devices have different addressing requirements, etc.). You
> could then use bus_dmamem_alloc() to allocate your buffers.
certainly i don't want to use netmap with bounce buffers.
I am not sure about IOMMU (I basically don't need it but maybe
using a compatible API is always nice). Right now i am allocating
a huge chunk of memory with contigmalloc.
Ryan Stone suggested that a plain malloc may work as well (as long
as i make sure that each buffer is within a single page).
Eventually I may want to play with cache alignment (also suggested by Ryan)
so allocate smaller chunks of contigmalloc'ed memory (say each buffer
is 2K - 64 bytes, then a contiguous block of 64K fits exactly 33 buffers).
cheers
luigi
may also work as long as i make sure th
>
> --
> John Baldwin
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