Messages in this thread |  | | From | Marco Elver <> | Date | Fri, 27 Nov 2020 13:26:35 +0100 | Subject | Re: [PATCH net-next] net: switch to storing KCOV handle directly in sk_buff |
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On Thu, 26 Nov 2020 at 17:35, Willem de Bruijn <willemdebruijn.kernel@gmail.com> wrote: > On Thu, Nov 26, 2020 at 3:19 AM Marco Elver <elver@google.com> wrote: [...] > > Will send v2. > > Does it make more sense to revert the patch that added the extensions > and the follow-on fixes and add a separate new patch instead?
That doesn't work, because then we'll end up with a build-broken commit in between the reverts and the new version, because mac80211 uses skb_get_kcov_handle().
> If adding a new field to the skb, even if only in debug builds, > please check with pahole how it affects struct layout if you > haven't yet.
Without KCOV:
/* size: 224, cachelines: 4, members: 72 */ /* sum members: 217, holes: 1, sum holes: 2 */ /* sum bitfield members: 36 bits, bit holes: 2, sum bit holes: 4 bits */ /* forced alignments: 2 */ /* last cacheline: 32 bytes */
With KCOV:
/* size: 232, cachelines: 4, members: 73 */ /* sum members: 225, holes: 1, sum holes: 2 */ /* sum bitfield members: 36 bits, bit holes: 2, sum bit holes: 4 bits */ /* forced alignments: 2 */ /* last cacheline: 40 bytes */
> The skb_extensions idea was mine. Apologies for steering > this into an apparently unsuccessful direction. Adding new fields > to skb is very rare because possibly problematic wrt allocation.
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