linux-kernel - Re: [PATCH v3] vmstat: Kernel stack usage histogram

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Message-ID: <9f044745-aa8f-5fff-66c6-4b24521967c8@google.com>
Date: Fri, 19 Jul 2024 20:41:55 -0700 (PDT)
From: David Rientjes <rientjes@...gle.com>
To: Pasha Tatashin <pasha.tatashin@...een.com>
cc: Shakeel Butt <shakeel.butt@...ux.dev>, akpm@...ux-foundation.org, 
    jpoimboe@...nel.org, kent.overstreet@...ux.dev, peterz@...radead.org, 
    nphamcs@...il.com, cerasuolodomenico@...il.com, surenb@...gle.com, 
    lizhijian@...itsu.com, willy@...radead.org, vbabka@...e.cz, ziy@...dia.com, 
    linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v3] vmstat: Kernel stack usage histogram

On Thu, 18 Jul 2024, Pasha Tatashin wrote:

> On Thu, Jul 18, 2024 at 7:19 PM Shakeel Butt <shakeel.butt@...ux.dev> wrote:
> >
> > Hi Pasha,
> >
> > On Wed, Jul 17, 2024 at 12:50:00PM GMT, Pasha Tatashin wrote:
> > > On Wed, Jun 12, 2024 at 2:50 PM Shakeel Butt <shakeel.butt@...ux.dev> wrote:
> > > >
> > [...]
> > > > >
> > > > > One more question: Is there any concern in making
> > > > > CONFIG_DEBUG_STACK_USAGE not a debug feature i.e. enable in default
> > > > > kernels instead of just debug kernels?
> > >
> > > We enabled it in Google ProdKernel. There is some overhead when
> > > threads are exiting, because we are looking for the first non-zero
> > > byte, but that is minimal. We haven't observed any performance impact
> > > on our fleet.
> > >
> >
> > So, you would support making CONFIG_DEBUG_STACK_USAGE enabled by
> > default, right?
> 
> Right, I see nothing wrong with having this enabled by default.
> 

The benefits of enabling CONFIG_DEBUG_STACK_USAGE by default would 
certainly outweigh any theoretical performance downside, I strongly favor 
enabling it by default and was surprised to find it hidden behind 
debugging when I enabled it in Google's production fleet.