[syslinux] Measuring boot time

[Gene Cumm]

On Mon, Oct 5, 2015 at 5:08 PM, Geert Stappers via Syslinux
<syslinux at zytor.com> wrote:
> On Mon, Oct 05, 2015 at 08:36:17PM +0000, Tal Lubko via Syslinux wrote:
>> Hi
>> Some time ago I wrote this mailing list about some extra time that it
>> takes for my system to boot
>
> And meanwhile there where many, many e-mail on this mailinglist.
> So thank you for bringing another (good) reason to reply _below_ the text.

This becomes more evident when you attempt to read the mailing list
archive.  It reads like a clean story.  Conversation view helps
subscribers (like mysefl) but it's still easier to read _in_ the
context.

>> and I don't know where it came from.
>
> Yes, please elaborate.
>
>
>> I'm using a custom BIOS which loads at 1 second and now I've found out
>> that it takes for the bootloader and OS an extra 1 second to load when
>> keyboard is disconnected.I got from the BIOS engineer the following
>> explanation and steps to take:

>> In syslinux make sure that it doesn???t use the KBC at all.
>> KBC functions will timeout when a KBC is not present.
>> GATEA20 (address line A20 wrap around 8086 compatibility gate) must
>> not be controlled by KBC as first option. No menu stuff or something
>> needing keyboard should be used.

This makes a lot of sense.  Systems without a keyboard and/or keyboard
controller are relatively rare although it feels like increasing in
popularity.  I merged a commit resolving a similar issue for EFI last
month.

>> The GATEA20 should be enabled as follows:
>>
>> 1) Test if A20 is already enabled. If enabled goto 7.
>> 2) Do BIOS int 0x15 function 0x2401 to enable GATEA20.
>> 3) Test if A20 is enabled. If enabled go to 7.
>> 4) Do port 0x92 (FASTA20) enable.
>> 5) Test if A20 is enabled. If enabled go to 7.
>> 6) Error!!
>> 7) A20 is enabled. Done.

>> However, I'm not sure what's the best way to do that.I've seen that
>> there is GATEA20 related code only in GPXE branch but I'm not using
>> GPXE.

>> Any suggestions?
>
> Another BIOS???

If this is the BIOS engineer's answer, I'm lead to believe the
attempts to drain the keyboard controller's buffer are slowing you
down.  This code would be early in execution and could be ASM or C.

-- 
-Gene