From: Pavel Machek <pavel@ucw.cz>
To: Matteo Croce <mcroce@linux.microsoft.com>
Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
linux-arch@vger.kernel.org,
Paul Walmsley <paul.walmsley@sifive.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>,
Atish Patra <atish.patra@wdc.com>,
Emil Renner Berthing <kernel@esmil.dk>,
Akira Tsukamoto <akira.tsukamoto@gmail.com>,
Drew Fustini <drew@beagleboard.org>,
Bin Meng <bmeng.cn@gmail.com>,
David Laight <David.Laight@aculab.com>,
Guo Ren <guoren@kernel.org>, Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v5 1/3] riscv: optimized memcpy
Date: Fri, 1 Oct 2021 13:23:54 +0200 [thread overview]
Message-ID: <20211001112354.GA10720@duo.ucw.cz> (raw)
In-Reply-To: <20210929172234.31620-2-mcroce@linux.microsoft.com>
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Hi!
> From: Matteo Croce <mcroce@microsoft.com>
>
> 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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next prev parent reply other threads:[~2021-10-01 11:24 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-29 17:22 [PATCH v5 0/3] riscv: optimized mem* functions Matteo Croce
2021-09-29 17:22 ` [PATCH v5 1/3] riscv: optimized memcpy Matteo Croce
2021-09-30 1:24 ` Guo Ren
2021-09-30 1:36 ` Matteo Croce
2021-09-30 19:43 ` Vineet Gupta
2021-10-01 8:06 ` David Laight
2021-10-01 11:23 ` Pavel Machek [this message]
2021-10-02 17:20 ` Matteo Croce
2021-09-29 17:22 ` [PATCH v5 2/3] riscv: optimized memmove Matteo Croce
2021-09-29 17:22 ` [PATCH v5 3/3] riscv: optimized memset Matteo Croce
2021-11-25 10:56 ` Ley Foon Tan
2021-12-06 20:37 ` Emil Renner Berthing
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