RELENG_10 performance regression (was Re: 35-40% performance drop releng9 vs releng10 openvpn

[Xin Li]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA512

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 <delphij at delphij.net>    https://www.delphij.net/
FreeBSD - The Power to Serve!           Live free or die
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2.1.2 (FreeBSD)
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=Uxnt
-----END PGP SIGNATURE-----