linux-kernel - Re: [PATCH v8 06/14] lockdep: Detect and handle hist

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Message-ID: <20170814072900.GL20323@X58A-UD3R>
Date:   Mon, 14 Aug 2017 16:29:00 +0900
From:   Byungchul Park <byungchul.park@....com>
To:     Boqun Feng <boqun.feng@...il.com>
Cc:     Byungchul Park <max.byungchul.park@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>, tglx@...utronix.de,
        Michel Lespinasse <walken@...gle.com>, kirill@...temov.name,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-mm@...ck.org, akpm@...ux-foundation.org, willy@...radead.org,
        npiggin@...il.com, kernel-team@....com
Subject: Re: [PATCH v8 06/14] lockdep: Detect and handle hist_lock ring
 buffer overwrite

On Mon, Aug 14, 2017 at 03:05:22PM +0800, Boqun Feng wrote:
> > 1. Boqun's approach
> 
> My approach requires(additionally):
> 
> 	MAX_XHLOCKS_NR * sizeof(unsigned int) // because of the hist_id field in hist_lock
> 
> bytes per task.
> 
> > 2. Peterz's approach
> 
> And Peter's approach requires(additionally):
> 
> 	1 * sizeof(unsigned int)
> 
> bytes per task.
> 
> So basically we need some tradeoff between memory footprints and history
> precision here.

I see what you intended. Then, Peterz's one looks better.