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On 03/20/15 17:15, Konstantin Belousov wrote:
>> For the purpose of devfs, does it make sense to bump timestamps
>> like normal filesystems for each read/write operation? Looks
>> like Mac OS X will bump timestamps for each operation but Debian
>> don't.
>
> First question is, what timecounter hardware is used. I would
> accept some slowdown from hardware like HPET, but it is indeed
> surprising if caused by TSC.
It was HPET (see earlier discussion where a FlameGraph is posted).
I've done a survey on a few other operating systems, including
OpenIndiana, Debian and OS X. Neither OpenIndiana nor Debian update
timestamp for read/write events so I'd propose this change to make it
a runtime configurable behavior and disable by default:
https://reviews.freebsd.org/D2104
Cheers,
- --
Xin LI <delp...@delphij.net> https://www.delphij.net/
FreeBSD - The Power to Serve! Live free or die
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