linux-kernel - Re: [PATCH v3 31/35] lib: add memory allocations report in show

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Date: Thu, 15 Feb 2024 20:18:06 -0500
From: Kent Overstreet <kent.overstreet@...ux.dev>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Vlastimil Babka <vbabka@...e.cz>, 
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Subject: Re: [PATCH v3 31/35] lib: add memory allocations report in show_mem()

On Thu, Feb 15, 2024 at 08:12:39PM -0500, Steven Rostedt wrote:
> On Thu, 15 Feb 2024 19:50:24 -0500
> Kent Overstreet <kent.overstreet@...ux.dev> wrote:
> 
> > > All nice, but where are the benchmarks? This looks like it will have an
> > > affect on cache and you can talk all you want about how it will not be an
> > > issue, but without real world benchmarks, it's meaningless. Numbers talk.  
> > 
> > Steve, you're being demanding. We provided sufficient benchmarks to show
> > the overhead is low enough for production, and then I gave you a
> > detailed breakdown of where our overhead is and where it'll show up. I
> > think that's reasonable.
> 
> It's not unreasonable or demanding to ask for benchmarks. You showed only
> micro-benchmarks that do not show how cache misses may affect the system.
> Honestly, it sounds like you did run other benchmarks and didn't like the
> results and are fighting to not have to produce them. Really, how hard is
> it? There's lots of benchmarks you can run, like hackbench, stress-ng,
> dbench. Why is this so difficult for you?

Woah, this is verging into paranoid conspiracy territory.

No, we haven't done other benchmarks, and if we had we'd be sharing
them. And if I had more time to spend on performance of this patchset
that's not where I'd be spending it; the next thing I'd be looking at
would be assembly output of the hooking code and seeing if I could shave
that down.

But I already put a ton of work into shaving cycles on this patchset,
I'm happy with the results, and I have other responsibilities and other
things I need to be working on.