linux-kernel - Re: [PATCH 1/3] lockdep: Apply crossrelease to PG

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Message-ID: <cf8aa555-7435-ea00-a4ee-3dcfd33ab5a0@lge.com>
Date:   Thu, 16 Nov 2017 21:48:05 +0900
From:   Byungchul Park <byungchul.park@....com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     peterz@...radead.org, mingo@...nel.org, akpm@...ux-foundation.org,
        tglx@...utronix.de, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-block@...r.kernel.org,
        kernel-team@....com, jack@...e.cz, jlayton@...hat.com,
        viro@...iv.linux.org.uk, hannes@...xchg.org, npiggin@...il.com,
        rgoldwyn@...e.com, vbabka@...e.cz, pombredanne@...b.com,
        vinmenon@...eaurora.org, gregkh@...uxfoundation.org
Subject: Re: [PATCH 1/3] lockdep: Apply crossrelease to PG_locked locks

On 11/16/2017 9:02 PM, Michal Hocko wrote:
> for each struct page. So you are doubling the size. Who is going to
> enable this config option? You are moving this to page_ext in a later
> patch which is a good step but it doesn't go far enough because this
> still consumes those resources. Is there any problem to make this
> kernel command line controllable? Something we do for page_owner for
> example?

Sure. I will add it.

> Also it would be really great if you could give us some measures about
> the runtime overhead. I do not expect it to be very large but this is

The major overhead would come from the amount of additional memory
consumption for 'lockdep_map's.

Do you want me to measure the overhead by the additional memory
consumption?

Or do you expect another overhead?

Could you tell me what kind of result you want to get?

> something people are usually interested in when enabling debugging
> features.

-- 
Thanks,
Byungchul