Hi!
> From: Matteo Croce <mcroce@xxxxxxxxxxxxx>
>
> Write a C version of memcpy() which uses the biggest data size allowed,
> without generating unaligned accesses.
>
> The procedure is made of three steps:
> First copy data one byte at time until the destination buffer is aligned
> to a long boundary.
> Then copy the data one long at time shifting the current and the next u8
> to compose a long at every cycle.
> Finally, copy the remainder one byte at time.
>
> On a BeagleV, the TCP RX throughput increased by 45%:
>
> before:
>
> $ iperf3 -c beaglev
> Connecting to host beaglev, port 5201
> [ 5] local 192.168.85.6 port 44840 connected to 192.168.85.48 port 5201
> [ ID] Interval Transfer Bitrate Retr Cwnd
> [ 5] 0.00-1.00 sec 76.4 MBytes 641 Mbits/sec 27 624 KBytes
> [ 5] 1.00-2.00 sec 72.5 MBytes 608 Mbits/sec 0 708 KBytes
>
> after:
>
> $ iperf3 -c beaglev
> Connecting to host beaglev, port 5201
> [ 5] local 192.168.85.6 port 44864 connected to 192.168.85.48 port 5201
> [ ID] Interval Transfer Bitrate Retr Cwnd
> [ 5] 0.00-1.00 sec 109 MBytes 912 Mbits/sec 48 559 KBytes
> [ 5] 1.00-2.00 sec 108 MBytes 902 Mbits/sec 0 690
> KBytes
That's really quite cool. Could you see if it is your "optimized
unaligned" copy doing the difference?>
+/* convenience union to avoid cast between different pointer types */
> +union types {
> + u8 *as_u8;
> + unsigned long *as_ulong;
> + uintptr_t as_uptr;
> +};
> +
> +union const_types {
> + const u8 *as_u8;
> + unsigned long *as_ulong;
> + uintptr_t as_uptr;
> +};
Missing consts here?
Plus... this is really "interesting" coding style. I'd just use casts
in kernel.
Regards, Pavel
--
http://www.livejournal.com/~pavelmachek
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