Re: [PATCH 0/2] Historical Service Time Path Selector

From: Gabriel Krisman Bertazi
Date: Sun Apr 26 2020 - 16:04:25 EST


Mike Snitzer <snitzer@xxxxxxxxxx> writes:

>
> Looks like you've put a lot of time to this and I'd be happy to help
> you get this to land upstream.
>
> But... (you knew there'd be at least one "but" right? ;) I'm not
> liking making this path selector request-based specific. All other
> selectors up to this point are request-based vs bio-based agnostic.
>
> Would you be open to dropping patch 1/2 and replacing it with
> something like the following patch?
>
> Then you'd pass 'u64 start_time_ns' into the path_selector_type's
> .end_io (and possibly .start_io).

I think it is fine.

Kind of a MD newbie question, but if I understand correctly,
dm_start_time_ns_from_clone is only for bio based multipath, and we just
pass req->io_start_time directly on request based multipath, right? If
I understand the code correctly, start_io_acct is only called for the
bio level DM.

I will update the patches, do a quick round of tests with BIO based and
send a v2.

Thanks a lot,

--
Gabriel Krisman Bertazi