svn commit: r326731 - head/sys/ufs/ffs

[Warner Losh]

On Dec 9, 2017 4:27 PM, "Poul-Henning Kamp" <phk at 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


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Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
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