Re: [dm-devel] [PATCH] dm-bufio

[Joe Thornber <thornber redhat com>]

On Mon, Oct 17, 2011 at 10:04:16AM -0400, Mikulas Patocka wrote:
> > If you're going to use cond_resched() at least do so a little more
> > intelligently than putting it in _every_ loop.  For instance you call it on
> > every iteration of a sweep through the hash table.  The call to
> > cond_resched will take more time than the loop body.  At least make a
> > change so it's only done every n'th iteration.
> 
> I think it would be better to use
> #ifndef CONFIG_PREEMPT
> if (need_resched()) cond_resched();
> #endif
> 
> need_resched() is inlined and translates to a single condition.

Yep, that would be fine.

> I don't know why Linux doesn't provide a macro for it, this would be 
> useful far beyond dm code.

Agreed, I was very surprised that cond_resched() expands out to a
function call rather than a test + fn call.

Get a patch together and I'll merge.

- Joe