Booting uncompressed kernel image on i386?

Booting uncompressed kernel image on i386?

[Ondrej Zary]

Is there an easy way to boot uncompressed kernel (2.6) image instead of 
the compressed one (bzImage) - using e.g. LILO?
I'm trying to do that because the decompression takes about 15 seconds 
on my i386 (it's really an i386 - i386DX/25 :-) The uncompressed kernel 
is about 1.5MB. I've already tried compressing it using gzip -1 instead 
of gzip -9 but that didn't make decompression any faster.


-- 
Ondrej Zary

Re: Booting uncompressed kernel image on i386?

[Ondrej Zary]

[-- Attachment #1: Type: text/plain, Size: 608 bytes --]

Ondrej Zary wrote:
> Is there an easy way to boot uncompressed kernel (2.6) image instead of 
> the compressed one (bzImage) - using e.g. LILO?
> I'm trying to do that because the decompression takes about 15 seconds 
> on my i386 (it's really an i386 - i386DX/25 :-) The uncompressed kernel 
> is about 1.5MB. I've already tried compressing it using gzip -1 instead 
> of gzip -9 but that didn't make decompression any faster.
> 
Nobody answered, time to look at the code :-)
The attached patch is a quick hack so "make" will create uncompressed 
kernel that can be booted in regular way.


-- 
Ondrej Zary

[-- Attachment #2: uncompressed-kernel.patch --]
[-- Type: text/plain, Size: 1098 bytes --]

--- linux-2.6.12-printserver/scripts/Makefile.lib	2005-06-28 12:45:20.000000000 +0200
+++ linux-2.6.12-pentium/scripts/Makefile.lib	2005-07-01 23:36:30.000000000 +0200
@@ -177,7 +177,7 @@
 # ---------------------------------------------------------------------------
 
 quiet_cmd_gzip = GZIP    $@
-cmd_gzip = gzip -f -9 < $< > $@
+cmd_gzip = cat < $< > $@
 
 # ===========================================================================
 # Generic stuff
--- linux-2.6.12-printserver/arch/i386/boot/compressed/misc.c	2005-06-17 21:48:29.000000000 +0200
+++ linux-2.6.12-pentium/arch/i386/boot/compressed/misc.c	2005-07-01 23:34:55.000000000 +0200
@@ -374,7 +374,15 @@
 
 	makecrc();
 	putstr("Uncompressing Linux... ");
-	gunzip();
+	int i;
+	for (i = 0; i < input_len / WSIZE; i++) {
+		memcpy(window, input_data+i*WSIZE, WSIZE);
+		outcnt = WSIZE;
+		flush_window();
+	}
+	memcpy(window, input_data+i*WSIZE, input_len % WSIZE);
+	outcnt = input_len % WSIZE;
+	flush_window();
 	putstr("Ok, booting the kernel.\n");
 	if (high_loaded) close_output_buffer_if_we_run_high(mv);
 	return high_loaded;

Re: Booting uncompressed kernel image on i386?

[Wakko Warner]

Ondrej Zary wrote:
> Nobody answered, time to look at the code :-)
> The attached patch is a quick hack so "make" will create uncompressed 
> kernel that can be booted in regular way.

> --- linux-2.6.12-printserver/arch/i386/boot/compressed/misc.c	2005-06-17 21:48:29.000000000 +0200
> +++ linux-2.6.12-pentium/arch/i386/boot/compressed/misc.c	2005-07-01 23:34:55.000000000 +0200
> @@ -374,7 +374,15 @@
>  
>  	makecrc();
>  	putstr("Uncompressing Linux... ");

Would it not make sense to remove the above line?  You're not actually
uncompressing anything.

> -	gunzip();
> +	int i;
> +	for (i = 0; i < input_len / WSIZE; i++) {
> +		memcpy(window, input_data+i*WSIZE, WSIZE);
> +		outcnt = WSIZE;
> +		flush_window();
> +	}
> +	memcpy(window, input_data+i*WSIZE, input_len % WSIZE);
> +	outcnt = input_len % WSIZE;
> +	flush_window();
>  	putstr("Ok, booting the kernel.\n");
>  	if (high_loaded) close_output_buffer_if_we_run_high(mv);
>  	return high_loaded;

-- 
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Re: Booting uncompressed kernel image on i386?

[Ondrej Zary]

Wakko Warner wrote:
> Ondrej Zary wrote:
> 
>>Nobody answered, time to look at the code :-)
>>The attached patch is a quick hack so "make" will create uncompressed 
>>kernel that can be booted in regular way.
> 
> 
>>--- linux-2.6.12-printserver/arch/i386/boot/compressed/misc.c	2005-06-17 21:48:29.000000000 +0200
>>+++ linux-2.6.12-pentium/arch/i386/boot/compressed/misc.c	2005-07-01 23:34:55.000000000 +0200
>>@@ -374,7 +374,15 @@
>> 
>> 	makecrc();
>> 	putstr("Uncompressing Linux... ");
> 
> 
> Would it not make sense to remove the above line?  You're not actually
> uncompressing anything.
> 
It would but I kept it there for debugging (to see where it crashed :-)
Anyway, I'd like to add new target "make uImage" (or something like 
that) but that requires more work. Something like this might be 
interesting for embedded systems which want to minimalize boot time.

>>-	gunzip();
>>+	int i;
>>+	for (i = 0; i < input_len / WSIZE; i++) {
>>+		memcpy(window, input_data+i*WSIZE, WSIZE);
>>+		outcnt = WSIZE;
>>+		flush_window();
>>+	}
>>+	memcpy(window, input_data+i*WSIZE, input_len % WSIZE);
>>+	outcnt = input_len % WSIZE;
>>+	flush_window();
>> 	putstr("Ok, booting the kernel.\n");
>> 	if (high_loaded) close_output_buffer_if_we_run_high(mv);
>> 	return high_loaded;
> 
> 


-- 
Ondrej Zary