[LU-11825] Remove LU-8964/pio feature & supporting framework

• Type: Bug
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.13.0, Lustre 2.12.1
• Severity: 3
• Assignee: Patrick Farrell
• Reporter: Patrick Farrell

Description

As discussed recently on the lustre-devel mailing list:

http://lists.lustre.org/pipermail/lustre-devel-lustre.org/2018-November/008230.html

http://lists.lustre.org/pipermail/lustre-devel-lustre.org/2018-November/008231.html

http://lists.lustre.org/pipermail/lustre-devel-lustre.org/2018-November/008233.html

http://lists.lustre.org/pipermail/lustre-devel-lustre.org/2018-November/008234.html

I think the pio feature should be removed.

Quoting my email to the list:
"

elieve that long term it’s headed out of Lustre. It only improves performance in a limited way in certain circumstances, and harms it in various others. So it’s off by default, and, I suspect, remains completely unused. A while back I noticed its test framework test didn’t activate it correctly, and once fixed, it sometimes deadlocks (race with truncate). There’s a patch to fix that, but a problem was found in it and it has since languished.

I would still suggest you take it, Neil, as othewise you’ll complicate a bunch of potentially nasty porting working in the CLIO stack, as you apply the years of patches written with it there. Instead, I’d suggest we pull it in the open sfs branch (Sorry! It was a promising idea but it hasn’t panned out, and the current parallel readahead work isn’t going to use it.) and then eventually you could pick that up."

Patches forthcoming.  I have also asked the lustre-discuss mailing list if anyone is using it, and we can change course if someone pipes up.

Issue Links

• is related to: LU-12503 LustreError: 19435:0:(vvp_io.c:1056:vvp_io_write_start()) LBUG
• is related to: LU-10367 FIO Fails to run with libaio
• is related to: LU-10923 cl_io_loop improperly assumes all ios are rw-type IOs
• is related to: LU-12262 Improve sbi_flags checking
• is related to: LU-8964 use parallel I/O to improve performance on machines with slow single thread performance