Messages in this thread Patch in this message | | | From | Matteo Croce <> | Date | Fri, 9 Apr 2021 22:44:50 +0200 | Subject | Re: [PATCH net-next 2/3] net: use skb_for_each_frag() helper where possible |
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On Fri, Apr 9, 2021 at 8:54 PM Jakub Kicinski <kuba@kernel.org> wrote: > > On Fri, 9 Apr 2021 20:06:04 +0200 Matteo Croce wrote: > > From: Matteo Croce <mcroce@microsoft.com> > > > > use the new helper macro skb_for_each_frag() which allows to iterate > > through all the SKB fragments. > > > > The patch was created with Coccinelle, this was the semantic patch: > > Bunch of set but not used warnings here. Please make sure the code > builds cleanly allmodconfig, W=1 C=1 before posting. >
Will do.
> What pops to mind (although quite nit picky) is the question if the > assembly changes much between driver which used to cache nr_frags and > now always going skb_shinfo(skb)->nr_frags? It's a relatively common > pattern.
Since skb_shinfo() is a macro and skb_end_pointer() a static inline, it should be the same, but I was curious to check so, this is a diff between the following snippet before and afer the macro:
int frags = skb_shinfo(skb)->nr_frags; int i; for (i = 0; i < frags; i++) kfree(skb->frags[i]);
1 file changed, 8 insertions(+), 7 deletions(-)
--- ins1.s 2021-04-09 22:35:59.384523865 +0200 +++ ins2.s 2021-04-09 22:36:08.132594737 +0200 @@ -1,26 +1,27 @@ iter: movsx rax, DWORD PTR [rdi+16] mov rdx, QWORD PTR [rdi+8] mov eax, DWORD PTR [rdx+rax] test eax, eax jle .L6 push rbp - sub eax, 1 + mov rbp, rdi push rbx - lea rbp, [rdi+32+rax*8] - lea rbx, [rdi+24] + xor ebx, ebx sub rsp, 8 .L3: - mov rdi, QWORD PTR [rbx] - add rbx, 8 + mov rdi, QWORD PTR [rbp+24+rbx*8] + add rbx, 1 call kfree - cmp rbx, rbp - jne .L3 + movsx rax, DWORD PTR [rbp+16] + mov rdx, QWORD PTR [rbp+8] + cmp DWORD PTR [rdx+rax], ebx + jg .L3 add rsp, 8 xor eax, eax pop rbx pop rbp ret .L6: xor eax, eax ret -- per aspera ad upstream
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