linux-kernel - Re: [RFC 0/3] ARM: copy_{from,to}

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Date:   Fri, 12 Jun 2020 21:31:12 +0530
From:   afzal mohammed <afzal.mohd.ma@...il.com>
To:     Nicolas Pitre <nico@...xnic.net>
Cc:     Russell King - ARM Linux admin <linux@...linux.org.uk>,
        Arnd Bergmann <arnd@...db.de>,
        Linus Walleij <linus.walleij@...aro.org>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-arm-kernel@...ts.infradead.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>
Subject: Re: [RFC 0/3] ARM: copy_{from,to}_user() for vmsplit 4g/4g

Hi,

On Fri, Jun 12, 2020 at 11:19:23AM -0400, Nicolas Pitre wrote:
> On Fri, 12 Jun 2020, afzal mohammed wrote:

> > Performance wise, results are not encouraging, 'dd' on tmpfs results,

> Could you compare with CONFIG_UACCESS_WITH_MEMCPY as well?

                 512     1K      4K     16K     32K     64K     1M
 
normal           30      46      89     95      90      85      65

uaccess_w_memcpy 28.5    45      85     92      91      85      65

w/ series        22      36      72     79      78      75      61

There are variations in the range +/-2 in some readings when repeated,
not put above, to keep comparison simple.

Regards
afzal