From: Matteo Croce <mcroce@linux.microsoft.com>
To: Pavel Machek <pavel@ucw.cz>
Cc: linux-riscv <linux-riscv@lists.infradead.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-arch <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: Sat, 2 Oct 2021 19:20:24 +0200 [thread overview]
Message-ID: <CAFnufp3uD7Wx=TnHYFaHBCy3mQu08zvv2NO=dws=tOMkKTpKCA@mail.gmail.com> (raw)
In-Reply-To: <20211001112354.GA10720@duo.ucw.cz>
On Fri, Oct 1, 2021 at 1:23 PM Pavel Machek <pavel@ucw.cz> wrote:
>
> 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.
>
Yes, the one for as_ulong is missing.
By using casts I had to use too many of them, making repeated
assignments in every function.
This is basically the same, with less code :)
Cheers,
--
per aspera ad upstream
next prev parent reply other threads:[~2021-10-02 17:21 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
2021-10-02 17:20 ` Matteo Croce [this message]
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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