From owner-svn-src-all@freebsd.org Fri Aug 25 17:59:32 2017 Return-Path: Delivered-To: svn-src-all@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 9A39EDDD990; Fri, 25 Aug 2017 17:59:32 +0000 (UTC) (envelope-from freebsd@pdx.rh.CN85.dnsmgr.net) Received: from pdx.rh.CN85.dnsmgr.net (br1.CN84in.dnsmgr.net [69.59.192.140]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 78AC8698CD; Fri, 25 Aug 2017 17:59:31 +0000 (UTC) (envelope-from freebsd@pdx.rh.CN85.dnsmgr.net) Received: from pdx.rh.CN85.dnsmgr.net (localhost [127.0.0.1]) by pdx.rh.CN85.dnsmgr.net (8.13.3/8.13.3) with ESMTP id v7PHxLSe070179; Fri, 25 Aug 2017 10:59:21 -0700 (PDT) (envelope-from freebsd@pdx.rh.CN85.dnsmgr.net) Received: (from freebsd@localhost) by pdx.rh.CN85.dnsmgr.net (8.13.3/8.13.3/Submit) id v7PHxKPD070178; Fri, 25 Aug 2017 10:59:20 -0700 (PDT) (envelope-from freebsd) From: "Rodney W. Grimes" Message-Id: <201708251759.v7PHxKPD070178@pdx.rh.CN85.dnsmgr.net> Subject: Re: svn commit: r322863 - head/sys/cam In-Reply-To: To: Warner Losh Date: Fri, 25 Aug 2017 10:59:20 -0700 (PDT) CC: Slawa Olhovchenkov , Warner Losh , src-committers , "svn-src-all@freebsd.org" , "svn-src-head@freebsd.org" Reply-To: rgrimes@freebsd.org X-Mailer: ELM [version 2.4ME+ PL121h (25)] MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=US-ASCII X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 25 Aug 2017 17:59:32 -0000 [ Charset UTF-8 unsupported, converting... ] > On Fri, Aug 25, 2017 at 7:35 AM, Slawa Olhovchenkov wrote: > > > On Thu, Aug 24, 2017 at 10:11:10PM +0000, Warner Losh wrote: > > > > > Author: imp > > > Date: Thu Aug 24 22:11:10 2017 > > > New Revision: 322863 > > > URL: https://svnweb.freebsd.org/changeset/base/322863 > > > > > > Log: > > > Expand the latency tracking array from 1.024s to 8.192s to help track > > > extreme outliers from dodgy drives. Adjust comments to reflect this, > > > and make sure that the number of latency buckets match in the two > > > places where it matters. > > > > May be up to 1min? > > > > I'm not sure what additional data you'll get between "totally sucks, at > least 8s latency" and "totally sucks, at least 32s." or "totally sucks, at > least 64s" though the latter isn't possible with the default timeouts... > > I'm planning on adding a 'max' latency that's self-resetting instead of > expanding the bucket upwards. I'm also contemplating expanding it down to > 100us or even 10us since nda serves nvme drives which easily can be sub > 100us. > > Warner What about using a log2/log10 engineering style binning of 1, 2, 4, 8 us 10, 20, 40, 80 us 100, 200, 400, 800 us ... 10000000, 20000000, 40000000, 80000000 us This would give you a fairly fine grain in the high speed area and cource grain in the not very likely areas, and it all fits in a nice 32 ints. -- Rod Grimes rgrimes@freebsd.org