HPET vs other timers
Poul-Henning Kamp
phk at phk.freebsd.dk
Sun Jun 3 08:55:56 UTC 2007
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@ 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.
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