From: Anshuman Khandual <anshuman.khandual@arm.com>
To: Mike Rapoport <rppt@linux.ibm.com>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>,
Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@kernel.org>,
Dave Hansen <dave.hansen@intel.com>,
Vladimir Murzin <vladimir.murzin@arm.com>,
Tony Luck <tony.luck@intel.com>,
Dan Williams <dan.j.williams@intel.com>
Subject: Re: early_memtest() patterns
Date: Wed, 27 Mar 2019 16:51:28 +0530 [thread overview]
Message-ID: <2f272c22-8453-7637-f744-632e70404e61@arm.com> (raw)
In-Reply-To: <20190326135420.GA23024@rapoport-lnx>
On 03/26/2019 07:24 PM, Mike Rapoport wrote:
> On Tue, Mar 26, 2019 at 01:39:14PM +0530, Anshuman Khandual wrote:
>> Hello,
>>
>> early_memtest() is being executed on many platforms even though they dont enable
>> CONFIG_MEMTEST by default. Just being curious how the following set of patterns
>> got decided. Are they just random 64 bit patterns ? Or there is some particular
>> significance to them in detecting bad memory.
>>
>> static u64 patterns[] __initdata = {
>> /* The first entry has to be 0 to leave memtest with zeroed memory */
>> 0,
>> 0xffffffffffffffffULL,
>> 0x5555555555555555ULL,
>> 0xaaaaaaaaaaaaaaaaULL,
>> 0x1111111111111111ULL,
>> 0x2222222222222222ULL,
>> 0x4444444444444444ULL,
>> 0x8888888888888888ULL,
>> 0x3333333333333333ULL,
>> 0x6666666666666666ULL,
>> 0x9999999999999999ULL,
>> 0xccccccccccccccccULL,
>> 0x7777777777777777ULL,
>> 0xbbbbbbbbbbbbbbbbULL,
>> 0xddddddddddddddddULL,
>> 0xeeeeeeeeeeeeeeeeULL,
>> 0x7a6c7258554e494cULL, /* yeah ;-) */
>> };
>>
>> BTW what about the last one here.
> It's 'LINUXrlz' ;-)
Yeah eventually figured that. Though first 16 patterns switch on/off individual
bits on a given byte, there does not seem to be any order or pattern to it.
Never mind, was just curious.
prev parent reply other threads:[~2019-03-27 11:21 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-26 8:09 Anshuman Khandual
2019-03-26 8:40 ` Michal Hocko
2019-03-26 13:54 ` Mike Rapoport
2019-03-27 11:21 ` Anshuman Khandual [this message]
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