linux-kernel - Re: [PATCH 09/28] nios2: Page table management

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Message-ID: <CAFiDJ5_gcSfJT1Dphc6kizkExssvkd4Pdd40iDZpr9J7Y55g-g@mail.gmail.com>
Date:	Tue, 22 Apr 2014 16:09:46 +0800
From:	Ley Foon Tan <lftan@...era.com>
To:	Pavel Machek <pavel@...x.de>
Cc:	linux-arch@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-doc@...r.kernel.org, cltang@...esourcery.com
Subject: Re: [PATCH 09/28] nios2: Page table management

Hi

On Sun, Apr 20, 2014 at 12:05 AM, Pavel Machek <pavel@...x.de> wrote:

>> +static void pgd_init(pgd_t *pgd)
>> +{
>> +     unsigned long *p = (unsigned long *) pgd;
>> +     int i;
>> +
>> +     for (i = 0; i < USER_PTRS_PER_PGD; i += 8) {
>> +             p[i + 0] = (unsigned long) invalid_pte_table;
>> +             p[i + 1] = (unsigned long) invalid_pte_table;
>> +             p[i + 2] = (unsigned long) invalid_pte_table;
>> +             p[i + 3] = (unsigned long) invalid_pte_table;
>> +             p[i + 4] = (unsigned long) invalid_pte_table;
>> +             p[i + 5] = (unsigned long) invalid_pte_table;
>> +             p[i + 6] = (unsigned long) invalid_pte_table;
>> +             p[i + 7] = (unsigned long) invalid_pte_table;
>> +     }
>
> Umm. Manual loop unrolling. Does it really improve performance? Is the
> code hot enough to warrant the uglyness?
We can use the memset here because invalid_pte_table is full 32 bit value.
BTW, arch for score and mips have the similar implementation as well.

Regards
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