linux-kernel - Re: [PATCH] mm: rate-limit allocation failure warnings more aggressively

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Message-ID: <alpine.DEB.2.21.1910281725270.114830@chino.kir.corp.google.com>
Date:   Mon, 28 Oct 2019 17:27:00 -0700 (PDT)
From:   David Rientjes <rientjes@...gle.com>
To:     Johannes Weiner <hannes@...xchg.org>
cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, kernel-team@...com
Subject: Re: [PATCH] mm: rate-limit allocation failure warnings more
 aggressively

On Mon, 28 Oct 2019, Johannes Weiner wrote:

> While investigating a bug related to higher atomic allocation
> failures, we noticed the failure warnings positively drowning the
> console, and in our case trigger lockup warnings because of a serial
> console too slow to handle all that output.
> 
> But even if we had a faster console, it's unclear what additional
> information the current level of repetition provides.
> 
> Allocation failures happen for three reasons: The machine is OOM, the
> VM is failing to handle reasonable requests, or somebody is making
> unreasonable requests (and didn't acknowledge their opportunism with
> __GFP_NOWARN). Having the memory dump, a callstack, and the ratelimit
> stats on skipped failure warnings should provide enough information to
> let users/admins/developers know whether something is wrong and point
> them in the right direction for debugging, bpftracing etc.
> 
> Limit allocation failure warnings to 1 spew every ten seconds.
> 
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>

Acked-by: David Rientjes <rientjes@...gle.com>

It feels like the vmalloc warnings should be treated with their own 
ratelimit (pass a struct ratelimit_state * to warn_alloc()) but that's 
outside the scope of this particular change.