Messages in this thread | | | Date | Wed, 23 Dec 2009 09:42:53 +0100 | From | Ingo Molnar <> | Subject | Re: workqueue thing |
| |
* Tejun Heo <tj@kernel.org> wrote:
> Hello, Ingo. > > On 12/23/2009 05:12 PM, Ingo Molnar wrote: > > > > * Ingo Molnar <mingo@elte.hu> wrote: > > > >> At least as far as i'm concerned, i'd like to see actual uses. It's a big > >> linecount increase all things considered: > >> > >> 20 files changed, 2783 insertions(+), 660 deletions(-) > > BTW, the code contains way more comment afterwards and has other benefits > like not having crazy number of workers around on many core machines.
(the original workqueue.c had way more comments as well.)
> >> and you say it _wont_ help performance/scalability (this aspect wasnt clear > > And I think it will help scalability for sure although it depends on > what type of scalability you're talking about.
_I_ am not making any claims - i am simply asking what the benefits are, just to move the discussion forward. If there are benefits, it must be measurable, simple as that.
> >> to me from previous discussions), so the (yet to be seen) complexity > >> reduction in other code ought to be worth it. > > > > To further stress this point, i'd like to point to the very first commit that > > introduced kernel/workqueue.c into Linux 7 years ago: > > > > | From 6ed12ff83c765aeda7d38d3bf9df7d46d24bfb11 Mon Sep 17 00:00:00 2001 > > | From: Ingo Molnar <mingo@elte.hu> > > | Date: Mon, 30 Sep 2002 22:17:42 -0700 > > | Subject: [PATCH] [PATCH] Workqueue Abstraction > > > > look at the diffstat of that commit: > > > > 201 files changed, 1102 insertions(+), 1194 deletions(-) > > > > despite adding a new abstraction and kernel subsystem (workqueues), that > > commit modified more than a hundred drivers to make use of it, and managed to > > achieve a net linecount decrease of 92 lines - despite adding hundreds of > > lines of a new core facility. > > > > Likewise, for this particular patchset it should be possible to identify > > existing patterns of code in the existing code base of 6+ millions lines of > > Linux driver code that would make the advantages of this +2000 lines of core > > kernel code plain obvious. There were multipe claims of problems with the > > current abstractions - so there sure must be a way to show off the new code in > > I'm not sure I'm gonna update that many places in a single sweep but yeah > let's give it a shot.
In all fairness the original workqueue.c had an advantage, that it basically piggybacked on usable patterns from the tqueue (task-queue) abstraction - and that was rather repetitive.
Your code adds a new _paradigm_ for which no easily reusable patterns exist - so under no way are you expected to show such a massive amount of conversion - just a handful of cases would be enough to show the benefits - we can extrapolate from there.
It would also give us hands-on experience with the utility (and robustness) of your proposal, so it's a win-win proposal IMO.
Thanks,
Ingo
| |