Date: Fri, 20 Mar 2015 17:28:15 -0700 From: Xin Li <delphij@delphij.net> To: Konstantin Belousov <kostikbel@gmail.com>, d@delphij.net Cc: John-Mark Gurney <jmg@funkthat.com>, FreeBSD-STABLE Mailing List <freebsd-stable@freebsd.org>, John Baldwin <jhb@freebsd.org> Subject: Re: RELENG_10 performance regression (was Re: 35-40% performance drop releng9 vs releng10 openvpn Message-ID: <550CBB1F.8010601@delphij.net> In-Reply-To: <20150321001559.GB2379@kib.kiev.ua> References: <5506250A.2000506@sentex.net> <20150316132055.GQ32288@funkthat.com> <5509D6C6.4050204@sentex.net> <20150318211457.GL51048@funkthat.com> <550B6950.8060806@sentex.net> <550C5AAF.9060502@sentex.net> <550C8AEE.4090408@sentex.net> <550CB306.7030405@delphij.net> <20150321001559.GB2379@kib.kiev.ua>
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-----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@delphij.net> https://www.delphij.net/ FreeBSD - The Power to Serve! Live free or die -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.1.2 (FreeBSD) iQIcBAEBCgAGBQJVDLscAAoJEJW2GBstM+nsGtMQAKyh3kW6VWPnCd353KELqeoE 3n295iHqVjAF6vszt71cfiAqlz0oSH+5i2SfR1LKVXH4cb2gMbXYbMeJVQiV7L93 8xEsBNtPF4Z/fxwyEBfFb3WcXHo+TGjvaCEbsuJIFKhqa4GPY230/7JELN/LXuNd HJlP7YECNPgeVWyYuCdZkLu/BMOPjL44/wcC/YuXSQP65TK54kx59KLg671o9Z2R ffpljAmJSqpNjas41qyVN+SNxr9ga8oQA0LTf8lbn3r4o2mx+te8yzNcyIn/gCU8 jawDGfGNiEvCTr76ST6rvELy4jFbmZyNFrbu+TA6VDT2/CCh1x5qhDceXTnZKPtX iJFpDKsl87R5aXdRQjwCZKkTdaJ7AuRAG0lrmumxIlblgDmaDsVbmaqR1CU0JzWI rvGblL6iwm/4pL+O9Igkr6oN6+yd1/9KM2yCB5BZDokLnoj6INWOft4z6jGyOUWh T3oNVfB48g/j5NKRyU/vFvJIUix2mbE5ziem+RyLU6x/UOdYQJsKRIlN6xPiIx73 /G7kpT1JbsoS47fyere5jeUV2UOurRuH5UfBHjJCJ0X44tzrsMhTm3Vs2cOzJP7K 6SNbyxyCbX3uJN1Aq9nhg2scIVieV1/BRLoeI6LEVVZKTTig4LA8ekzb0P6e1Fwg f9rvXNwpdeZPmsDwdpff =Uxnt -----END PGP SIGNATURE-----
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