Date: Fri, 15 Apr 2016 01:10:51 +0300 (MSK) From: Dmitry Morozovsky <marck@rinet.ru> To: Warner Losh <imp@bsdimp.com> Cc: "svn-src-head@freebsd.org" <svn-src-head@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>, src-committers <src-committers@freebsd.org>, Warner Losh <imp@freebsd.org> Subject: Re: svn commit: r298002 - in head/sys: cam cam/ata cam/scsi conf dev/ahci Message-ID: <alpine.BSF.2.00.1604150107500.76365@woozle.rinet.ru> In-Reply-To: <CANCZdfp8iJJoVZd-xQXqxpVsB5PiocTTcFVW-Vxkn6zX3OMUfw@mail.gmail.com> References: <201604142147.u3ELlwYo052010@repo.freebsd.org> <alpine.BSF.2.00.1604150051440.76365@woozle.rinet.ru> <CANCZdfp8iJJoVZd-xQXqxpVsB5PiocTTcFVW-Vxkn6zX3OMUfw@mail.gmail.com>
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Warner, On Thu, 14 Apr 2016, Warner Losh wrote: > You add CAM_NETFLIX_IOSCHED to your kernel config to enable it. Hmmm, > looking at the diff, perhaps I should add that to LINT. > > In production, we use it for three things. First, our scheduler keeps a lot > more statistics than the default one. These statistics are useful for us > knowing when a system is saturated and needs to shed load. Second, we favor > reads over writes because our workload, as you might imagine, is a read > mostly work load. Finally, in some systems, we throttle the write throughput > to the SSDs. The SSDs we buy can do 300MB/s write while serving 400MB/s read, > but only for short periods of time (long enough to do 10-20GB of traffic). > After that, write performance drops, and read performance goes out the > window. Experiments have shown that if we limit the write speed to no more > than 30MB/s or so, then the garbage collection the drive is doing won't > adversely affect the read latency / performance. > https://people.freebsd.org/~imp/bsdcan2015/iosched-v3.pdf Thank you again for clarifications! I'd reacted because we're @work possibly can see similar (while not nearly as comparable loads, of course!) patterns. > > This code has run in production at Netflix for over a year now. > > > > Looking at this: could it be possibly targeted for MFCing? > > While this has been running in 10.x stable for the past year on our servers, > I have no plans to MFC it at this time. Great, at least it could be played with then! ;) -- Sincerely, D.Marck [DM5020, MCK-RIPE, DM3-RIPN] [ FreeBSD committer: marck@FreeBSD.org ] ------------------------------------------------------------------------ *** Dmitry Morozovsky --- D.Marck --- Wild Woozle --- marck@rinet.ru *** ------------------------------------------------------------------------
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