On Tue, Sep 3, 2024 at 2:40 PM Jakub Kicinski <kuba@xxxxxxxxxx> wrote:
>
> On Sat, 31 Aug 2024 00:43:08 +0000 Mina Almasry wrote:
> > static inline bool tcp_skb_can_collapse_to(const struct sk_buff *skb)
> > {
> > - return likely(!TCP_SKB_CB(skb)->eor);
> > + return likely(!TCP_SKB_CB(skb)->eor && skb_frags_readable(skb));
>
> Do you remember why this is here?
Yeah, to be honest, when I first implemented some of these checks I
erred on the side of caution, and added checks around anything that
looked concerning, some of these unnecessary checks got removed, but
looks like this one didn't.
> Both for Rx and Tx what should matter
> is whether the "readability" matches, right? We can merge two unreadable
> messages.
Yes, you're right, only 'readability matches' should be the criteria
here. `tcp_skb_can_collapse` already checks readability is matching
correctly, so no issue there. The `tcp_skb_can_collapse_to` check
you're commenting on here looks unnecessary. I will remove it and run
that through some testing.
As an aside, it looks to me like that tcp_skb_can_collapse_to
callsites don't seem to be doing any collapsing. Unless I misread the
code. It looks like tcp_skb_can_collapse_to is used as an eor check. I
can rename the function to tcp_skb_is_eor() or something if that makes
sense (in a separate patch). I think the name of the function confused
me slightly and made me think I need to do a readability check.
--
Thanks,
Mina
