linux-kernel - Re: [PATCH -next 0/5] rbtree: optimize frequent tree walks

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Message-Id: <20200210143546.4491d9715f1c4a0a1de999ca@linux-foundation.org>
Date:   Mon, 10 Feb 2020 14:35:46 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Davidlohr Bueso <dave@...olabs.net>
Cc:     linux-kernel@...r.kernel.org, mcgrof@...nel.org,
        broonie@...nel.org, alex.williamson@...hat.com
Subject: Re: [PATCH -next 0/5] rbtree: optimize frequent tree walks

On Mon, 10 Feb 2020 07:56:11 -0800 Davidlohr Bueso <dave@...olabs.net> wrote:

> On Sun, 09 Feb 2020, Andrew Morton wrote:
> >Seems that all the caller sites you've converted use a fairly small
> >number of rbnodes, so the additional storage shouldn't be a big
> >problem.  Are there any other sites you're eyeing?  If so, do you expect
> >any of those will use a significant amount of memory for the nodes?
> 
> I also thought about converting the deadline scheduler to use these,
> mainly benefiting pull_dl_task() but didn't get to it and I don't expect
> the extra footprint to be prohibitive.
> 
> >
> >And...  are these patches really worth merging?  Complexity is added,
> >but what end-user benefit can we expect?
> 
> Yes they are worth merging, imo (which of course is biased :)
> 
> I don't think there is too much added complexity overall, particularly
> considering that the user conversions are rather trivial. And even for
> small trees (ie 100 nodes) we still benefit in a measurable way from
> these optimizations.
> 

Measurable for microbenchmarks, I think?  But what benefit will a user
see, running a workload that is cared about?