linux-kernel - Re: [PATCH v2] mm/slub: disable slab merging in the default configuration

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Message-ID: <17349901-df3a-494e-fa71-2584d92526b5@google.com>
Date:   Thu, 6 Jul 2023 00:38:31 -0700 (PDT)
From:   David Rientjes <rientjes@...gle.com>
To:     Julian Pidancet <julian.pidancet@...cle.com>
cc:     Christoph Lameter <cl@...ux.com>,
        "Lameter, Christopher" <cl@...amperecomputing.com>,
        Pekka Enberg <penberg@...nel.org>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>, linux-mm@...ck.org,
        Jonathan Corbet <corbet@....net>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, Matthew Wilcox <willy@...radead.org>,
        Kees Cook <keescook@...omium.org>,
        Rafael Aquini <aquini@...hat.com>
Subject: Re: [PATCH v2] mm/slub: disable slab merging in the default
 configuration

On Mon, 3 Jul 2023, David Rientjes wrote:

> hackbench

Running hackbench on Skylake with v6.1.30 (A) and v6.1.30 + your patch 
(B), for example:

              LABEL             | COUNT |    MIN     |    MAX     |    MEAN    |   MEDIAN   |  STDDEV   |   DIRECTION    
--------------------------------+-------+------------+------------+------------+------------+-----------+----------------
  SReclaimable                  |       |            |            |            |            |           |                
  (A) v6.1.30                   | 11    | 129480.000 | 233208.000 | 189936.364 | 204316.000 | 31465.625 |                
  (B) <same sha>                | 11    | 139084.000 | 236772.000 | 198931.273 | 213672.000 | 30013.204 |                
                                |       | +7.42%     | +1.53%     | +4.74%     | +4.58%     | -4.62%    | <not defined>  
  SUnreclaim                    |       |            |            |            |            |           |                
  (A) v6.1.30                   | 11    | 305400.000 | 538744.000 | 422148.000 | 449344.000 | 65005.045 |                
  (B) <same sha>                | 11    | 305780.000 | 518300.000 | 422219.636 | 450252.000 | 61245.137 |                
                                |       | +0.12%     | -3.79%     | +0.02%     | +0.20%     | -5.78%    | <not defined>  

Amount of reclaimable slab significantly increases which is likely not a 
problem because, well, it's reclaimable.  But I suspect we'll find other 
interesting data points with the other suggested benchmarks.

And benchmark results:

              LABEL             | COUNT |    MIN     |    MAX     |    MEAN    |   MEDIAN   |  STDDEV   |   DIRECTION    
--------------------------------+-------+------------+------------+------------+------------+-----------+----------------
  hackbench_process_pipes_234   |       |            |            |            |            |           |                
  (A) v6.1.30                   | 7     | 1.735      | 1.979      | 1.831      | 1.835      | 0.086291  |                
  (B) <same sha>                | 7     | 1.687      | 2.023      | 1.886      | 1.911      | 0.10276   |                
                                |       | -2.77%     | +2.22%     | +3.00%     | +4.14%     | +19.09%   | <not defined>  
  hackbench_process_pipes_max   |       |            |            |            |            |           |                
  (A) v6.1.30                   | 7     | 1.735      | 1.979      | 1.831      | 1.835      | 0.086291  |                
  (B) <same sha>                | 7     | 1.687      | 2.023      | 1.886      | 1.911      | 0.10276   |                
                                |       | -2.77%     | +2.22%     | +3.00%     | +4.14%     | +19.09%   | - is good      
  hackbench_process_sockets_234 |       |            |            |            |            |           |                
  (A) v6.1.30                   | 7     | 7.883      | 7.909      | 7.899      | 7.899      | 0.0087808 |                
  (B) <same sha>                | 7     | 7.872      | 7.961      | 7.907      | 7.904      | 0.028019  |                
                                |       | -0.14%     | +0.66%     | +0.10%     | +0.06%     | +219.09%  | <not defined>  
  hackbench_process_sockets_max |       |            |            |            |            |           |                
  (A) v6.1.30                   | 7     | 7.883      | 7.909      | 7.899      | 7.899      | 0.0087808 |                
  (B) <same sha>                | 7     | 7.872      | 7.961      | 7.907      | 7.904      | 0.028019  |                
                                |       | -0.14%     | +0.66%     | +0.10%     | +0.06%     | +219.09%  | - is good      
  hackbench_thread_pipes_234    |       |            |            |            |            |           |                
  (A) v6.1.30                   | 7     | 2.146      | 2.677      | 2.410      | 2.418      | 0.18143   |                
  (B) <same sha>                | 7     | 2.016      | 2.514      | 2.268      | 2.241      | 0.17474   |                
                                |       | -6.06%     | -6.09%     | -5.88%     | -7.32%     | -3.69%    | <not defined>  
  hackbench_thread_pipes_max    |       |            |            |            |            |           |                
  (A) v6.1.30                   | 7     | 2.146      | 2.677      | 2.410      | 2.418      | 0.18143   |               
  (B) <same sha>                | 7     | 2.016      | 2.514      | 2.268      | 2.241      | 0.17474   |                
                                |       | -6.06%     | -6.09%     | -5.88%     | -7.32%     | -3.69%    | - is good      
  hackbench_thread_sockets_234  |       |            |            |            |            |           |                
  (A) v6.1.30                   | 7     | 8.025      | 8.127      | 8.084      | 8.085      | 0.029755  |                
  (B) <same sha>                | 7     | 7.990      | 8.093      | 8.042      | 8.035      | 0.035152  |                
                                |       | -0.44%     | -0.42%     | -0.53%     | -0.62%     | +18.14%   | <not defined>  
  hackbench_thread_sockets_max  |       |            |            |            |            |           |                
  (A) v6.1.30                   | 7     | 8.025      | 8.127      | 8.084      | 8.085      | 0.029755  |                
  (B) <same sha>                | 7     | 7.990      | 8.093      | 8.042      | 8.035      | 0.035152  |                
                                |       | -0.44%     | -0.42%     | -0.53%     | -0.62%     | +18.14%   | - is good