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SubjectRe: [RFC PATCH 0/6] Convert all tasklets to workqueues
Ingo Molnar wrote:
> my argument was: workqueues are more scalable than tasklets in general.

Here is my argument: that is totally irrelevant to $subject, when it
comes to dealing with managing existing [network driver] behavior and
performance.

My overall objection is the attempt to replace apples with oranges.

Network drivers use tasklets TODAY. Each driver -- in particular
acenic, ns83820, and the 10Gbps drivers -- has been carefully tuned to
use tasklets, hardirqs, and perhaps NAPI too. Changing to workqueue
WILL affect network driver hot paths, yet I see no analysis or
measurement at all of the behavior differences.

If hackers are willing to revisit each network driver, rework the
tasklet code to something more sane [in your opinion], and TEST it, I
will review the patches and happily ACK away.

Given that I feel that course of action is unlikely (the preferred
alternative apparently being "I don't use these drivers, but surely my
changes are OK anyway"), I do not see how this effort can proceed as is.

Lots of time went into tuning these network drivers for the specific
thread model they use. Maybe that thread model is no longer in style.
Maybe modern machine behavior dictates a different approach. The point
is... you don't know.

Jeff


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