> Is not the max 64K as you test against XDP_UMEM_MAX_CHUNK_SIZE in
> xdp_umem_reg()?
The absolute max is 64K. In the case of HPAGE_SIZE < 64K, then it
would be HPAGE_SIZE.
> > diff --git a/include/net/xdp_sock.h b/include/net/xdp_sock.h
> > index e96a1151ec75..ed88880d4b68 100644
> > --- a/include/net/xdp_sock.h
> > +++ b/include/net/xdp_sock.h
> > @@ -28,6 +28,9 @@ struct xdp_umem {
> > struct user_struct *user;
> > refcount_t users;
> > u8 flags;
> > +#ifdef CONFIG_HUGETLB_PAGE
>
> Sanity check: have you tried compiling your code without this config set?
Yes. The CI does this also on one of the platforms (hence some of the
bot errors in v1).
> > static int xdp_umem_pin_pages(struct xdp_umem *umem, unsigned long address)
> > {
> > +#ifdef CONFIG_HUGETLB_PAGE
>
> Let us try to get rid of most of these #ifdefs sprinkled around the
> code. How about hiding this inside xdp_umem_is_hugetlb() and get rid
> of these #ifdefs below? Since I believe it is quite uncommon not to
> have this config enabled, we could simplify things by always using the
> page_size in the pool, for example. And dito for the one in struct
> xdp_umem. What do you think?
I used #ifdef for `page_size` in the pool for maximum performance when
huge pages are disabled. We could also not worry about optimizing this
uncommon case though since the performance impact is very small.
However, I don't find the #ifdefs excessive either.
> > +static void xp_check_dma_contiguity(struct xsk_dma_map *dma_map, u32 page_size)
> > {
> > - u32 i;
> > + u32 stride = page_size >> PAGE_SHIFT; /* in order-0 pages */
> > + u32 i, j;
> >
> > - for (i = 0; i < dma_map->dma_pages_cnt - 1; i++) {
> > - if (dma_map->dma_pages[i] + PAGE_SIZE == dma_map->dma_pages[i + 1])
> > - dma_map->dma_pages[i] |= XSK_NEXT_PG_CONTIG_MASK;
> > - else
> > - dma_map->dma_pages[i] &= ~XSK_NEXT_PG_CONTIG_MASK;
> > + for (i = 0; i + stride < dma_map->dma_pages_cnt;) {
> > + if (dma_map->dma_pages[i] + page_size == dma_map->dma_pages[i + stride]) {
> > + for (j = 0; j < stride; i++, j++)
> > + dma_map->dma_pages[i] |= XSK_NEXT_PG_CONTIG_MASK;
> > + } else {
> > + for (j = 0; j < stride; i++, j++)
> > + dma_map->dma_pages[i] &= ~XSK_NEXT_PG_CONTIG_MASK;
> > + }
>
> Still somewhat too conservative :-). If your page size is large you
> will waste a lot of the umem. For the last page mark all the 4K
> "pages" that cannot cross the end of the umem due to the max size of a
> packet with the XSK_NEXT_PG_CONTIG_MASK bit. So you only need to add
> one more for-loop here to mark this, and then adjust the last for-loop
> below so it only marks the last bunch of 4K pages at the end of the
> umem as not contiguous.
I don't understand the issue. The XSK_NEXT_PG_CONTIG_MASK bit is only
looked at if the descriptor actually crosses a page boundary. I don't
think the current implementation wastes any UMEM.
