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SubjectRe: [PATCH 1/3] tools/vm: fix Makefile multi-targets
On Wed, 11 Nov 2015, Sergey Senozhatsky wrote:

> > This doesn't purport to explain why -O2 was added or why it's needed for←
> > these tools.
>
> Hm, that was a sem-automatic action I saw no issues with (besides, I
> considered this to be too small for a separate patch). `slabinfo' can
> be used to collected extended '-X' measurements for gnuplot script
> e.g.
> `while [ 1 ]; do slabinfo -X >> stats; sleep 0.1s; done`
>
> so making it a bit lighter is sort of positive change, though I'm not
> married to this option.
>
>
> perf stats:
>
> -- OLD
>
> Performance counter stats for './slabinfo.old -X -B -N 100':
>
> 197.879348 task-clock (msec) # 0.969 CPUs utilized
> 22 context-switches # 0.111 K/sec
> 0 cpu-migrations # 0.000 K/sec
> 2,276 page-faults # 0.012 M/sec
> 182,916,015 cycles # 0.924 GHz
> <not supported> stalled-cycles-frontend
> <not supported> stalled-cycles-backend
> 259,843,733 instructions # 1.42 insns per cycle
> 53,949,755 branches # 272.640 M/sec
> 157,607 branch-misses # 0.29% of all branches
>
> 0.204190648 seconds time elapsed
>
>
> -- NEW (-O2)
>
> Performance counter stats for './slabinfo.new -X -B -N 100':
>
> 169.963546 task-clock (msec) # 0.977 CPUs utilized
> 9 context-switches # 0.053 K/sec
> 0 cpu-migrations # 0.000 K/sec
> 2,276 page-faults # 0.013 M/sec
> 153,582,826 cycles # 0.904 GHz
> <not supported> stalled-cycles-frontend
> <not supported> stalled-cycles-backend
> 218,505,232 instructions # 1.42 insns per cycle
> 45,410,422 branches # 267.177 M/sec
> 114,126 branch-misses # 0.25% of all branches
>
> 0.173921887 seconds time elapsed
>
>
> ./scripts/bloat-o-meter tools/vm/slabinfo.old tools/vm/slabinfo.new
> add/remove: 5/23 grow/shrink: 7/7 up/down: 6434/-9495 (-3061)
> function old new delta
> main 878 3699 +2821
> output_slabs 307 2075 +1768
> report 781 1905 +1124
> rename_slabs 167 333 +166
> read_slab_obj.isra - 131 +131
> ops.isra - 104 +104
> set_obj.isra - 102 +102
> read_obj 145 236 +91
> sort_slabs 414 478 +64
> slab_empty.part - 32 +32
> get_obj.part - 17 +17
> slab_numa 542 556 +14
> decode_numa_list 235 230 -5
> fatal 176 160 -16
> usage 17 - -17
> onoff 27 - -27
> show_tracking 193 162 -31
> get_obj_and_str 157 124 -33
> slab_size 43 - -43
> slab_mismatch 47 - -47
> get_obj 48 - -48
> slab_waste 56 - -56
> link_slabs 226 169 -57
> slab_activity 60 - -60
> slab_validate 63 - -63
> slab_shrink 63 - -63
> slab_empty 74 - -74
> first_line 74 - -74
> store_size 271 191 -80
> xtotals 142 - -142
> ops 145 - -145
> set_obj 162 - -162
> read_slab_obj 182 - -182
> find_one_alias 187 - -187
> sort_aliases 288 - -288
> alias 298 - -298
> debug_opt_scan 355 - -355
> slab_debug 870 - -870
> totals 4136 3198 -938
> slabcache 1289 - -1289
> read_slab_dir 1798 - -1798
> slab_stats 2047 - -2047
>
>
>
> I believe the remaining tools will not `suffer' as well.
> Do you prefer to remove -O2?
>

No, I have no objection to removing -O2. I'd prefer that the rationale be
included in the commit description, however.

Acked-by: David Rientjes <rientjes@google.com>
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