Re: HPET vs other timers

From: Poul-Henning Kamp <phk_at_phk.freebsd.dk>
Date: Sun, 03 Jun 2007 08:55:53 +0000
In message <46620B92.8020608_at_root.org>, Nate Lawson writes:
>Poul-Henning Kamp wrote:
>> Nate Lawson wrote:
>>>> Anyone able to speculate why though?  HPET only reads 32 bits from a
>>>> memory mapped region.  No locking or other requirements.  ACPI_timer
>>>> does multiple IO ops, which according to bde_at_ are much slower than
>>>> memory reads.  
>> 
>> HPET needs to do metastability mitigation and is not "just a read
>> from a memory mapped region".
>
>If it does, then it's not implemented yet:

It's implemented in hardware, that's why the read is so slow.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk_at_FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.
Received on Sun Jun 03 2007 - 06:55:56 UTC

This archive was generated by hypermail 2.4.0 : Wed May 19 2021 - 11:39:11 UTC