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From: Sascha Hauer <s.hauer@pengutronix.de>
To: Peter Korsgaard <jacmet@sunsite.dk>
Cc: barebox@lists.infradead.org
Subject: Re: [PATCH 01/12] ARM zImage: do memmap if possible
Date: Tue, 30 Mar 2010 11:20:24 +0200	[thread overview]
Message-ID: <20100330092024.GI2241@pengutronix.de> (raw)
In-Reply-To: <8739zjc6ci.fsf@macbook.be.48ers.dk>

Hi Peter,

On Mon, Mar 29, 2010 at 08:47:57PM +0200, Peter Korsgaard wrote:
> >>>>> "Sascha" == Sascha Hauer <s.hauer@pengutronix.de> writes:
> 
> Hi,
> 
>  Sascha>  	zimage = xmalloc(header.end);
>  Sascha>  	memcpy(zimage, &header, sizeof(header));
>  Sascha> -
>  Sascha> -	ret = read(fd, zimage + sizeof(header), header.end - sizeof(header));
>  Sascha> -	if (ret < header.end - sizeof(header)) {
>  Sascha> -		printf("could not read %s\n", argv[1]);
>  Sascha> -		goto err_out1;
>  Sascha> +	m = memmap(fd, PROT_READ);
>  Sascha> +	if (m != (void *)-1) {
>  Sascha> +		memcpy(zimage, m, header.end);
> 
> Here you're rereading the header as well, instead of everything past it
> like the normal case.

Yes, mostly because I was too lazy to calculate the offsets.

> 
> Does this give a significant boost? read() from something memmap'able
> (like NOR) boils down to a memcpy as well, right?

Hmm, with memmap it's 149ms and with read 156ms in my case. I think this
is because with memmap it goes down to a single memcpy whereas with read
we memcpy in chunks of 4k. I implemented this out of reflex, but maybe
it's really not worth the added complexity.

Sascha

-- 
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  reply	other threads:[~2010-03-30  9:20 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-03-29  9:36 Patches for next merge window Sascha Hauer
2010-03-29  9:36 ` [PATCH 01/12] ARM zImage: do memmap if possible Sascha Hauer
2010-03-29 18:47   ` Peter Korsgaard
2010-03-30  9:20     ` Sascha Hauer [this message]
2010-03-30 10:01       ` Peter Korsgaard
2010-03-30 12:18         ` Sascha Hauer
2010-03-29  9:36 ` [PATCH 02/12] nand_imx: use optimized memcpy Sascha Hauer
2010-03-29  9:36 ` [PATCH 03/12] nand_imx: Speed up sequential read Sascha Hauer
2010-03-29  9:36 ` [PATCH 04/12] imx_nand: use memcpy for copying from/to buffer Sascha Hauer
2010-03-29 10:42   ` Ivo Clarysse
2010-03-29  9:36 ` [PATCH 05/12] add unaligned access support Sascha Hauer
2010-03-29  9:36 ` [PATCH 06/12] add unlzo support Sascha Hauer
2010-03-30 11:04   ` Sascha Hauer
2010-03-29  9:36 ` [PATCH 07/12] add snprintf function Sascha Hauer
2010-03-29  9:36 ` [PATCH 08/12] echo: add -e option support Sascha Hauer
2010-03-30 11:45   ` Peter Korsgaard
2010-03-30 12:17     ` Sascha Hauer
2010-03-29  9:36 ` [PATCH 09/12] add process_escape_sequence function Sascha Hauer
2010-03-29  9:36 ` [PATCH 10/12] echo command: Add -e option Sascha Hauer
2010-03-29  9:36 ` [PATCH 11/12] hush: only remove backslashes introduced from glob Sascha Hauer
2010-03-29 10:00   ` Sascha Hauer
2010-03-29  9:36 ` [PATCH 12/12] hush: allow fancy prompts Sascha Hauer

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