Re: Plan: journalling fixes for WAPBL

[Jaromír Doleček <jaromir.dolecek%gmail.com@localhost>]

2017-01-02 18:31 GMT+01:00 David Holland <dholland-tech%netbsd.org@localhost>:
> Well, there's two things going on here. One is the parallelism limit,
> which you can work around by having more drives, e.g. in an array.
> The other is netbsd's 64k MAXPHYS issue, which is our own problem that
> we could put time into. (And in fact, it would be nice to get
> tls-maxphys into -8... anyone have time? I don't. sigh)

It would be very nice to have this intergrated, yes. It won't have
dramatic performance effect, but it's relatively low hanging fruit,
it's already almost done and we should just get rid of this arbitrary
system limit. I'd like to look into this, but I won't manage sooner
then autumn 2017 - I'd like to first work on FUA/DPO support, and then
SATA NCQ. I think those could have bigger performance impact.

I hope I'll have some patches to make FUA available for I/O for SCSI
drives by second half of feb, plus the changes for WAPBL to use it.
It's slightly difficult to DTRT with FUA on nested drivers like
raidframe/cgd/vnd, but maybe we can ignore those for the first
iteration :) I'll send a proposal once I figure details.

Jaromir