[syslinux] "Tick-counting" vs "Tick-less" timekeeping issues on VMs emulating BIOS PCs

[H. Peter Anvin]

On 03/01/16 21:11, H. Peter Anvin via Syslinux wrote:
> On 03/01/16 07:21, Patrick Masotta via Syslinux wrote:
>>
>> At the moment I'm seeing timing issues on TFTP transfers (lwIP depends
>> on the new interrupt based timer). I have consistently detected 
>>
>> multiple Requests, double ACKs, etc. All these problems seem to be
>>
>> sourced on the now unreliable timeouts.
>> I have used TFTP on the same (BIOS VM) scenarios with 3.X and TFTP 
>>
>> timing was always rock solid.
>>
>>
>> Sorry if this was discussed before, if not I'd like to ask (Peter) if 
>> there is any reason preventing us from going back to the "Tick-less" 
>> approach. Thanks.
>>
> 
> There are quite a few; primarily we simply cannot make lwIP
> (lpxelinux.0) work without it.  However, pxelinux.0 should not depend on
> this.
> 

Now, tickful timekeeping is wasteful, but this is a bootloader, and
functionality is the main concern.  The "tickless" version still
depended on the BIOS tick.

	-hpa