net: gro: minor optimization for dev_gro_receive()
While inspecting some perf report, I noticed that the compiler emits suboptimal code for the napi CB initialization, fetching and storing multiple times the memory for flags bitfield. This is with gcc 10.3.1, but I observed the same with older compiler versions. We can help the compiler to do a nicer work clearing several fields at once using an u32 alias. The generated code is quite smaller, with the same number of conditional. Before: objdump -t net/core/gro.o | grep " F .text" 0000000000000bb0 l F .text 0000000000000357 dev_gro_receive After: 0000000000000bb0 l F .text 000000000000033c dev_gro_receive v1 -> v2: - use struct_group (Alexander and Alex) RFC -> v1: - use __struct_group to delimit the zeroed area (Alexander) Signed-off-by: Paolo Abeni <pabeni@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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