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From: james.morse@arm.com (James Morse)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] kexec: Add --lite option
Date: Mon, 07 Dec 2015 13:16:06 +0000	[thread overview]
Message-ID: <56658696.6070103@arm.com> (raw)
In-Reply-To: <20151207114839.GF16406@dhcppc13.redhat.com>

Hi Pratyush,

On 07/12/15 11:48, Pratyush Anand wrote:
>> 1) When we execute kexec() system call in first kernel, at that time it
>> calculates sha256 on all the binaries [1]. It take almost un-noticeable time
>> (less than a sec) there.
>>
>> 2) When purgatory is executed then it re-calculates sha256 using same routines
>> [2] on same binary data as that of case (1). But, now it takes 10-20 sec
>> (depending of size of binaries)?
>>
>> Why did not it take same time with O2 + D-cache enabled? I think, we should be
>> able to achieve same time in second case as well. What is missing?

I haven't benchmarked this, but:

util_lib/sha256.c contains calls out to memcpy().
In your case 1, this will use the glibc version. In case 2, it will use
the version implemented in purgatory/string.c, which is a byte-by-byte copy.


Thanks,

James

WARNING: multiple messages have this Message-ID (diff)
From: James Morse <james.morse@arm.com>
To: Pratyush Anand <panand@redhat.com>
Cc: Geoff Levand <geoff@infradead.org>,
	kexec@lists.infradead.org, Simon Horman <horms@verge.net.au>,
	Vivek Goyal <vgoyal@redhat.com>,
	Petitboot@lists.ozlabs.org, Scott Wood <scottwood@freescale.com>,
	Dave Young <dyoung@redhat.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] kexec: Add --lite option
Date: Mon, 07 Dec 2015 13:16:06 +0000	[thread overview]
Message-ID: <56658696.6070103@arm.com> (raw)
In-Reply-To: <20151207114839.GF16406@dhcppc13.redhat.com>

Hi Pratyush,

On 07/12/15 11:48, Pratyush Anand wrote:
>> 1) When we execute kexec() system call in first kernel, at that time it
>> calculates sha256 on all the binaries [1]. It take almost un-noticeable time
>> (less than a sec) there.
>>
>> 2) When purgatory is executed then it re-calculates sha256 using same routines
>> [2] on same binary data as that of case (1). But, now it takes 10-20 sec
>> (depending of size of binaries)?
>>
>> Why did not it take same time with O2 + D-cache enabled? I think, we should be
>> able to achieve same time in second case as well. What is missing?

I haven't benchmarked this, but:

util_lib/sha256.c contains calls out to memcpy().
In your case 1, this will use the glibc version. In case 2, it will use
the version implemented in purgatory/string.c, which is a byte-by-byte copy.


Thanks,

James

_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec

  reply	other threads:[~2015-12-07 13:16 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-10-21 23:12 [PATCH] kexec: Add --lite option Geoff Levand
2015-10-22  0:02 ` Jeremy Kerr
2015-10-22  0:37   ` Geoff Levand
2015-11-05  6:20     ` Scott Wood
2015-10-22  3:17 ` Dave Young
2015-10-22 12:50   ` Vivek Goyal
2015-10-22 19:08     ` Geoff Levand
2015-11-05  5:56       ` Scott Wood
2015-12-07 11:45         ` Pratyush Anand
2015-12-07 11:48           ` Pratyush Anand
2015-12-07 11:48             ` Pratyush Anand
2015-12-07 13:16             ` James Morse [this message]
2015-12-07 13:16               ` James Morse
2015-12-07 14:07               ` Pratyush Anand
2015-12-07 14:07                 ` Pratyush Anand
2015-12-08  1:03                 ` Scott Wood
2015-12-08  1:03                   ` Scott Wood
2015-12-08 16:00                 ` James Morse
2015-12-08 16:00                   ` James Morse
2015-12-09  9:28                   ` Pratyush Anand
2015-12-09  9:28                     ` Pratyush Anand
2016-01-11 12:46                     ` Pratyush Anand
2016-01-11 12:46                       ` Pratyush Anand
2016-01-12  1:06                       ` Simon Horman
2016-01-12  1:06                         ` Simon Horman
2015-10-22 18:57   ` Geoff Levand
2015-10-22 19:04     ` Vivek Goyal
2015-10-23  9:46     ` Dave Young
2015-10-23 18:49       ` Geoff Levand
2015-10-23 19:02     ` Eric W. Biederman
2018-04-11 18:30 ` [PATCH v2] kexec: Add --no-checks option Geoff Levand
2018-04-19  8:38   ` Simon Horman

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