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SubjectRe: [PATCH] no need to check for NULL before calling kfree() -fs/ext2/

On Sun, 27 Mar 2005, Dave Jones wrote:

> Am I the only person who is completely fascinated by the
> effort being spent here micro-optimising something thats
> almost never in a path that needs optimising ?
> I'd be amazed if any of this masturbation showed the tiniest
> blip on a real workload, or even on a benchmark other than
> one crafted specifically to test kfree in a loop.
> That each occurance of this 'optimisation' also saves a handful
> of bytes in generated code is it's only real benefit afaics.
> Even then, if a functions cache performance is better off because
> we trimmed a few bytes from the tail of a function, I'd be
> completely amazed.

I agree, it's amazing that this is treated like a big issue, it's not, and
I never meant for it to be a matter of such debate.

The whole thing (viewed from where I'm sitting) started when I noticed a
few of those redundant NULL checks while reading code, thought I'd clean
them up since they were clearly not needed and submit those patches. When
those patches then got merged I thought "ok, so this is something that's
actually appreciated, guess I might as well do some more when I come
across them or maybe even seek them out and get rid of them once and for
all"... So I started doing that and more of the patches got merged which
(at least to me) confirmed that it was a worthwhile activity, until at
some point voices were raised in objection.

At that point I felt I needed to explain the "why" of why I was doing it
and try and show that it might actually be a bennefit (and I believe the
small test I wrote shows it to be either a bennefit in the usual case or
at worst a trivial performance hit in the not-so-common case).
What I'm trying to find out now is if there's a general consensus that
these patches are worthwile and wanted or if they are unwanted and I'm
wasting my time. If the patches are wanted I don't mind doing them, but
if they are not wanted I don't want to waste my time (nor anyone elses) on
them. So, if I could just get peoples comment on that "wanted vs
not-wanted" then I could get on with either producing some patches for
people or get on with other things and drop this... Or I guess I could
just go on making those patches, submit them and then just leave it in the
hands of the individual maintainers (which was more or less how I started

Jesper Juhl

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