Date: Mon, 20 Aug 2012 17:46:12 +0300 From: Mitya <mitya@cabletv.dp.ua> To: freebsd-hackers@freebsd.org, freebsd-net@freebsd.org Subject: Replace bcopy() to update ether_addr Message-ID: <50324DB4.6080905@cabletv.dp.ua>
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Hi.
I found some overhead code in /src/sys/net/if_ethersubr.c and
/src/sys/netgraph/ng_ether.c
It contains strings, like bcopy(src, dst, ETHER_ADDR_LEN);
When src and dst are "struct ether_addr*", and ETHER_ADDR_LEN equal 6.
This code call every time, when we send Ethernet packet.
On example, on my machine in invoked nearly 20K per second.
Why we are use bcopy(), to copy only 6 bytes?
Answer - in some architectures we are can not directly copy unaligned data.
I propose this solution.
In file /usr/src/include/net/ethernet.h add this lines:
static inline void ether_addr_copy(ether_addr* src, ether_addr* dst) {
#if defined(__i386__) || defined(__amd64__)
*dst = *src;
#else
bcopy(src, dst, ETHER_ADDR_LEN);
#endif
}
On platform i386 gcc produce like this code:
leal -30(%ebp), %eax
leal 6(%eax), %ecx
leal -44(%ebp), %edx
movl (%edx), %eax
movl %eax, (%ecx)
movzwl 4(%edx), %eax
movw %ax, 4(%ecx)
And clang produce this:
movl -48(%ebp), %ecx
movl %ecx, -26(%ebp)
movw -44(%ebp), %si
movw %si, -22(%ebp)
All this variants are much faster, than bcopy()
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