Re: [PATCH 08/17] blkcg: shoot down blkio_groups on elevator switch

[Tejun Heo]

On Mon, Jan 23, 2012 at 10:52:16AM -0500, Vivek Goyal wrote:
> Atleast throttling rules should not disappear over elevator switch. They
> are per device and not per IO scheduler. Think of losing nr_requests
> settings just because elevator switch happened.
> 
> Elevator switch can be low frequency but how would a user space know
> that elevator switch failed that's why we lost our rules and now lets
> put the rules back.

It's simple - store all the policy rules before switching elevators
and restore them afterwards regardless of success / failure.

> I am not sure how would we justify this that because of ease of programming
> in kernel, now user space is supposed to make sure that any programmed
> rules are still there and reprogram the cgroup if rules are gone for
> some reason.

Sanity in trade off?

-- 
tejun
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/