Date: Sun, 10 Dec 2017 00:17:03 +0000 From: "Poul-Henning Kamp" <phk@phk.freebsd.dk> To: Warner Losh <imp@bsdimp.com> Cc: Mark Johnston <markj@freebsd.org>, Andriy Gapon <avg@freebsd.org>, src-committers <src-committers@freebsd.org>, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r326731 - head/sys/ufs/ffs Message-ID: <73337.1512865023@critter.freebsd.dk> In-Reply-To: <CANCZdfrQPSey1h%2BX_09GNJaeZqsZh6FmDXe6avO66qKEfAL=Pg@mail.gmail.com> References: <201712091544.vB9FiVUI096790@repo.freebsd.org> <a1d303b4-14b8-6a3d-3648-96a69bed7144@FreeBSD.org> <20171209223713.GA15275@raichu> <CANCZdfrSLKpwj_YVP-8k%2BWcJKPGqdvjZbCJgTFXCgbY7_6QUqw@mail.gmail.com> <73189.1512862030@critter.freebsd.dk> <CANCZdfrQPSey1h%2BX_09GNJaeZqsZh6FmDXe6avO66qKEfAL=Pg@mail.gmail.com>
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-------- In message <CANCZdfrQPSey1h+X_09GNJaeZqsZh6FmDXe6avO66qKEfAL=3DPg@mail.gma= il.com>, Warner Losh writes: >That would be strange given that BIO_ORDERED is @gibbs baby ? > >Nah... I wrote the iosched code... and I find the concept somewhat flawed >since it is at the disk level, not the partition level, so it winds up >interfering with mixed traffic. And it really only makes sense for writes= , >but it affects reads. And it is a poor fit to Ata semantics, and not a lo= t >better for scsi. And for nvme it creates a bottleneck in hardware careful= ly >designed to be free of bottlenecks... Don't take my comment as an endorsement of BIO_ORDERED... I think ordering is strictly a consumer responsibility for exactly (and then some) of the reasons you mention. "End to end principle in systems design" and all that... -- = Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe = Never attribute to malice what can adequately be explained by incompetence= .
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