linux-kernel - Re: [PATCH v5 06/13] lockdep: Implement crossrelease feature

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Date:   Fri, 3 Mar 2017 10:32:38 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Byungchul Park <byungchul.park@....com>
Cc:     mingo@...nel.org, tglx@...utronix.de, walken@...gle.com,
        boqun.feng@...il.com, kirill@...temov.name,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        iamjoonsoo.kim@....com, akpm@...ux-foundation.org,
        npiggin@...il.com, kernel-team@....com,
        Michal Hocko <mhocko@...nel.org>,
        Nikolay Borisov <nborisov@...e.com>,
        Mel Gorman <mgorman@...e.de>
Subject: Re: [PATCH v5 06/13] lockdep: Implement crossrelease feature

On Fri, Mar 03, 2017 at 10:13:38AM +0100, Peter Zijlstra wrote:
> On Fri, Mar 03, 2017 at 09:14:16AM +0100, Peter Zijlstra wrote:
> 
> > That said; I'd be fairly interested in numbers on how many links this
> > avoids, I'll go make a check_redundant() version of the above and put a
> > proper counter in so I can see what it does for a regular boot etc..
> 
> Two boots + a make defconfig, the first didn't have the redundant bit
> in, the second did (full diff below still includes the reclaim rework,
> because that was still in that kernel and I forgot to reset the tree).
> 
> 
>  lock-classes:                         1168       1169 [max: 8191]
>  direct dependencies:                  7688       5812 [max: 32768]
>  indirect dependencies:               25492      25937
>  all direct dependencies:            220113     217512
>  dependency chains:                    9005       9008 [max: 65536]
>  dependency chain hlocks:             34450      34366 [max: 327680]
>  in-hardirq chains:                      55         51
>  in-softirq chains:                     371        378
>  in-process chains:                    8579       8579
>  stack-trace entries:                108073      88474 [max: 524288]
>  combined max dependencies:       178738560  169094640
> 
>  max locking depth:                      15         15
>  max bfs queue depth:                   320        329
> 
>  cyclic checks:                        9123       9190
> 
>  redundant checks:                                5046
>  redundant links:                                 1828
> 
>  find-mask forwards checks:            2564       2599
>  find-mask backwards checks:          39521      39789
> 

OK, last email, I promise, then I'll go bury myself in futexes.

 find-mask forwards checks:            2999
 find-mask backwards checks:          56134

Is with a clean kernel, which shows how many __bfs() calls we save by
doing away with that RECLAIM state. OTOH:

 lock-classes:                         1167 [max: 8191]
 direct dependencies:                  7254 [max: 32768]
 indirect dependencies:               23763
 all direct dependencies:            219093

Shows that the added reclaim class isn't entirely free either ;-)