Date: Sat, 9 Dec 2017 16:34:59 -0700 From: Warner Losh <imp@bsdimp.com> To: Poul-Henning Kamp <phk@phk.freebsd.dk> 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: <CANCZdfrQPSey1h%2BX_09GNJaeZqsZh6FmDXe6avO66qKEfAL=Pg@mail.gmail.com> In-Reply-To: <73189.1512862030@critter.freebsd.dk> 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>
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On Dec 9, 2017 4:27 PM, "Poul-Henning Kamp" <phk@phk.freebsd.dk> wrote: -------- In message <CANCZdfrSLKpwj_YVP-8k+WcJKPGqdvjZbCJgTFXCgbY7_6QUqw@ mail.gmail.com>, Warner Losh writes: >I also noticed that gsched doesn't take BIO_ORDERED into account when >sorting requests. Isilon has an I/O scheduler which has this problem >too > >I think the cam iosched ignores it too. 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 lot better for scsi. And for nvme it creates a bottleneck in hardware carefully designed to be free of bottlenecks... Warner Warner -- 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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