Re: [PATCH v5]: Improve performance of LZO hibernation
From: Bojan Smojver
Date: Wed Sep 28 2011 - 03:29:12 EST
On Wed, 2011-09-28 at 10:22 +0300, Pekka Enberg wrote:
> > + while(1) {
> > + wait_event(d->go, atomic_read(&d->ready) ||
> > + kthread_should_stop());
> > + if (kthread_should_stop())
> > + break;
>
> So... what happens to the hibernation process when 'kthread_should_stop()'
> returns true?
The compression/decompression threads stop by breaking out of the loop.
At least they should, right? Did I misread some docs here?
PS. I'm not really a kernel programmer, so I'm kinda stumbling my way
through all this.
> > + nthr = num_online_cpus() - 1;
> > + nthr = nthr > LZO_THREADS ? LZO_THREADS : (nthr < 1 ? 1 : nthr);
>
> That's probably one of the most unreadable uses of the ternary
> operator I've ever seen!
Sorry about that. I can simplify.
> What's going on here anyway? Why "num_online_cpus() - 1"? What's wrong with
>
> nr_threads = num_online_cpus();
> if (nr_threads > LZO_THREADS)
> nr_threads = LZO_THREADS;
We want to keep at least one CPU free for that I/O and for pulling the
other threads into sync when they are done (that is if we have more than
one), right?
> [ And yes, please use less cryptic variable names. ]
OK, been pulled over for that before. Will fix.
> Overall, I really like your patch!
Thanks, hopefully it doesn't blow up too many file systems :-)
--
Bojan
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