linux-kernel - Re: [PATCH] mm: ratelimit oversized kvmalloc warnings instead of once

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Date: Tue, 18 Jun 2024 14:44:50 -0700
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>, 
	Michal Hocko <mhocko@...nel.org>, kernel-team@...a.com, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org, Kyle McMartin <kyle@...radead.org>
Subject: Re: [PATCH] mm: ratelimit oversized kvmalloc warnings instead of once

On Tue, Jun 18, 2024 at 02:40:10PM GMT, Linus Torvalds wrote:
> On Tue, 18 Jun 2024 at 14:34, Shakeel Butt <shakeel.butt@...ux.dev> wrote:
> >
> > Simply replace WARN_ON_ONCE with WARN_RATELIMIT.
> 
> NAK.
> 
> Sadly, the RATELIMIT cases are useless.
> 
> The normal rate limiting is basically "burst of up to ten, every five seconds".
> 
> That's going to completely swamp things and hide any other issue.
> 
> If we ratelimit it to "at most 1 per hour", maybe something like that
> would be acceptable.

"at most 1 per hour" sounds good.

> 
> But honestly, I do not understand your "first abuser only" complaint.
> There should not be *any* abusers. So just fix that first one already.
> 
> If you have more than one, you have bigger issues. So what is the real
> reason for this broken patch? Why didn't you fix the first one?
> 

The issue is the turnaround time to fix the first abuser and deploy the
fixed kernel to big enough fleet to find the remaining abusers. Usually
this turnaround time is in months.