On Tue, May 7, 2024 at 2:40 PM Alexander Lobakin <aleksander.loba...@intel.com> wrote: > > In fact, this structure contains a flexible array at the end, but > historically its size, alignment etc., is calculated manually. > There are several instances of the structure embedded into other > structures, but also there's ongoing effort to remove them and we > could in the meantime declare &net_device properly. > Declare the array explicitly, use struct_size() and store the array > size inside the structure, so that __counted_by() can be applied. > Don't use PTR_ALIGN(), as SLUB itself tries its best to ensure the > allocated buffer is aligned to what the user expects. > Also, change its alignment from %NETDEV_ALIGN to the cacheline size > as per several suggestions on the netdev ML. > > bloat-o-meter for vmlinux: > > free_netdev 445 440 -5 > netdev_freemem 24 - -24 > alloc_netdev_mqs 1481 1450 -31 > > On x86_64 with several NICs of different vendors, I was never able to > get a &net_device pointer not aligned to the cacheline size after the > change. > > Signed-off-by: Alexander Lobakin <aleksander.loba...@intel.com> > ---
... > - p = kvzalloc(alloc_size, GFP_KERNEL_ACCOUNT | __GFP_RETRY_MAYFAIL); > - if (!p) > + sizeof_priv = ALIGN(sizeof_priv, SMP_CACHE_BYTES); If we have a __counted_by(priv_len), why do you ALIGN(sizeof_priv, SMP_CACHE_BYTES) ? If a driver pretends its private part is 4 bytes, we should get a warning if 20 bytes are used instead. You added two ____cacheline_aligned already in net_device already.
