Re: [PATCH] RCU for low latency (experimental)

Andrea Arcangeli
2004-03-24T23:33:39Z

On Thu, Mar 25, 2004 at 04:41:45AM +0530, Dipankar Sarma wrote:
> That was not 16 callbacks per tick, it was 16 callbacks in one
> batch of a single softirq. And then I reschedule the RCU tasklet

sorry so you're already using tasklets in current code? I misunderstood
the current code then.

> to process the rest. I am planning to vary this and see if we
> should do even less per softirq.

yes, I think 16 is too much, the softirq code should just retry 10
times, summing up to 160 callbacks. After you re-arm the tasklet the
first time, all other rearmed invocations should probably execute less
callbacks than 16.

it greatly depends on the number of times we retry a softirq before
giving up and offloading the work to ksoftirqd, that number is 10
currently (see MAX_SOFTIRQ_RESTART). The bigger that number, the less
callbacks you can execute per tasklet.