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From: Guenter Roeck <linux@roeck-us.net>
To: Akira Tsukamoto <akira.tsukamoto@gmail.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	Qiu Wenbo <qiuwenbo@kylinos.com.cn>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 1/1] riscv: __asm_copy_to-from_user: Optimize unaligned memory access and pipeline stall
Date: Mon, 19 Jul 2021 07:24:44 -0700	[thread overview]
Message-ID: <9a2bf544-2aaa-d175-bc0a-c8bcefd8141a@roeck-us.net> (raw)
In-Reply-To: <e1bb4768-5517-8ef3-eaf3-bbfc103fa918@gmail.com>

On 7/19/21 7:00 AM, Akira Tsukamoto wrote:
> 
> On 7/19/2021 10:51 PM, Guenter Roeck wrote:
>> Hi,
>>
>> On 7/19/21 5:53 AM, Akira Tsukamoto wrote:
>>>
>>> This patch will reduce cpu usage dramatically in kernel space especially
>>> for application which use sys-call with large buffer size, such as
>>> network applications. The main reason behind this is that every
>>> unaligned memory access will raise exceptions and switch between s-mode
>>> and m-mode causing large overhead.
>>>
>>
>> I had to revert the original patch from the mainline kernel prior to applying
>> this patch. Obviously that means that there may be other changes affecting the
>> outcome.
>>
>> riscv64 images work, but riscv32 images still fail with this patch applied.
>> The error is a bit different than before, though.
>>
>> ...
>> [   11.899979] Run /sbin/init as init process
>> [   12.152666] random: fast init done
>> moun: applet not found
>> "�����V�t: applet not found
>> /bi�����V�F-: applet not found
>> moun: applet not found
>> swaon: applet not found
>> hostname-F: applet not found
>>
>> After this, the image hangs.
>>
>> For comparison, the mainline kernel (v5.14-rc2) fails as follows.
>>
>> [   10.788105] Run /sbin/init as init process
>> Starting syslogd: OK
>> Starting klogd: OK
>> /etc/init.d/S02sysctl: line 68: syntax error: EOF in backquote substitution
>> /etc/init.d/S20urandom: line 1: syntax error: unterminated quoted string
>> Starting network: /bin/sh: syntax error: unterminated quoted string
>> sed: unmatched '/'
>> /bin/sh: syntax error: unterminated quoted string
>> FAIL
>> /etc/init.d/S55runtest: line 48: syntax error: EOF in backquote substitution
>>
>> I'll be happy to provide information on how to reproduce the problem
>> if needed. Please let me know.
> 
> Yes, I do would like to know the procedure of build instruction of your rv32 image.
> Then I would reproduce the error and look into how to fix it.
> 
Please have a look at http://server.roeck-us.net/qemu/riscv32/
and let me know if you need anything else.

Thanks,
Guenter

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  reply	other threads:[~2021-07-19 14:25 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-19 12:51 [PATCH v4 0/1] riscv: improving uaccess with logs from network bench Akira Tsukamoto
2021-07-19 12:53 ` [PATCH v4 1/1] riscv: __asm_copy_to-from_user: Optimize unaligned memory access and pipeline stall Akira Tsukamoto
2021-07-19 13:51   ` Guenter Roeck
2021-07-19 14:00     ` Akira Tsukamoto
2021-07-19 14:24       ` Guenter Roeck [this message]
2021-07-19 14:49         ` Akira Tsukamoto
2021-07-19 15:16           ` Guenter Roeck
2021-07-20  6:54             ` Akira Tsukamoto
2021-07-19 14:49   ` Geert Uytterhoeven
2021-07-19 15:22     ` Akira Tsukamoto
2021-07-19 14:55 ` [PATCH v4 0/1] riscv: improving uaccess with logs from network bench Akira Tsukamoto

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