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Date:   Fri, 12 Jun 2020 21:31:12 +0530
From:   afzal mohammed <afzal.mohd.ma@gmail.com>
To:     Nicolas Pitre <nico@fluxnic.net>
Cc:     Russell King - ARM Linux admin <linux@armlinux.org.uk>,
        Arnd Bergmann <arnd@arndb.de>,
        Linus Walleij <linus.walleij@linaro.org>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        linux-arm-kernel@lists.infradead.org,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>
Subject: Re: [RFC 0/3] ARM: copy_{from,to}_user() for vmsplit 4g/4g
Message-ID: <20200612160112.GA27659@afzalpc>
References: <cover.1591885760.git.afzal.mohd.ma@gmail.com>
 <nycvar.YSQ.7.77.849.2006121117250.3341460@knanqh.ubzr>
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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