On Thu, Jul 18, 2024 at 9:52 PM Praveen Kaligineedi
<pkaligineedi@xxxxxxxxxx> wrote:
>
> On Thu, Jul 18, 2024 at 4:07 PM Willem de Bruijn
> <willemdebruijn.kernel@xxxxxxxxx> wrote:
>
> > > + * segment, then it will count as two descriptors.
> > > + */
> > > + if (last_frag_size > GVE_TX_MAX_BUF_SIZE_DQO) {
> > > + int last_frag_remain = last_frag_size %
> > > + GVE_TX_MAX_BUF_SIZE_DQO;
> > > +
> > > + /* If the last frag was evenly divisible by
> > > + * GVE_TX_MAX_BUF_SIZE_DQO, then it will not be
> > > + * split in the current segment.
> >
> > Is this true even if the segment did not start at the start of the frag?
> The comment probably is a bit confusing here. The current segment
> we are tracking could have a portion in the previous frag. The code
> assumed that the portion on the previous frag (if present) mapped to only
> one descriptor. However, that portion could have been split across two
> descriptors due to the restriction that each descriptor cannot exceed 16KB.
>>> /* If the last frag was evenly divisible by
>>> + * GVE_TX_MAX_BUF_SIZE_DQO, then it will not be
>>> + * split in the current segment.
This is true because the smallest multiple of 16KB is 32KB, and the
largest gso_size at least for Ethernet will be 9K. But I don't think
that that is what is used here as the basis for this statement?
> That's the case this fix is trying to address.
> I will work on simplifying the logic based on your suggestion below so
> that the fix is easier to follow
