Re: HPET vs other timers

From: Poul-Henning Kamp <phk_at_phk.freebsd.dk>
Date: Sat, 02 Jun 2007 21:15:13 +0000
In message <20070602194151.GA1604_at_rot13.obsecurity.org>, Kris Kennaway writes:

>> 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".

-- 
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 Sat Jun 02 2007 - 19:15:23 UTC

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