[sj:damon/next 151/151] mm/damon/vaddr.c:196:13: warning: variable 'tidx' set but not used

[sj:damon/next 151/151] mm/damon/vaddr.c:196:13: warning: variable 'tidx' set but not used

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/sj/linux.git damon/next
head:   b617f1f8428697a2583fb6882864224d59a91bf2
commit: b617f1f8428697a2583fb6882864224d59a91bf2 [151/151] mm/damon/vaddr: remove debug message
config: m68k-allyesconfig (https://download.01.org/0day-ci/archive/20260711/202607111055.NqcvApT6-lkp@intel.com/config)
compiler: m68k-linux-gcc (GCC) 16.1.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260711/202607111055.NqcvApT6-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202607111055.NqcvApT6-lkp@intel.com/

All warnings (new ones prefixed by >>):

   mm/damon/vaddr.c: In function '__damon_va_init_regions':
>> mm/damon/vaddr.c:196:13: warning: variable 'tidx' set but not used [-Wunused-but-set-variable=]
     196 |         int tidx = 0;
         |             ^~~~


vim +/tidx +196 mm/damon/vaddr.c

3f49584b262cf8 SeongJae Park 2021-09-07  148  
3f49584b262cf8 SeongJae Park 2021-09-07  149  /*
3f49584b262cf8 SeongJae Park 2021-09-07  150   * Initialize the monitoring target regions for the given target (task)
3f49584b262cf8 SeongJae Park 2021-09-07  151   *
3f49584b262cf8 SeongJae Park 2021-09-07  152   * t	the given target
3f49584b262cf8 SeongJae Park 2021-09-07  153   *
3f49584b262cf8 SeongJae Park 2021-09-07  154   * Because only a number of small portions of the entire address space
3f49584b262cf8 SeongJae Park 2021-09-07  155   * is actually mapped to the memory and accessed, monitoring the unmapped
3f49584b262cf8 SeongJae Park 2021-09-07  156   * regions is wasteful.  That said, because we can deal with small noises,
3f49584b262cf8 SeongJae Park 2021-09-07  157   * tracking every mapping is not strictly required but could even incur a high
3f49584b262cf8 SeongJae Park 2021-09-07  158   * overhead if the mapping frequently changes or the number of mappings is
3f49584b262cf8 SeongJae Park 2021-09-07  159   * high.  The adaptive regions adjustment mechanism will further help to deal
3f49584b262cf8 SeongJae Park 2021-09-07  160   * with the noise by simply identifying the unmapped areas as a region that
3f49584b262cf8 SeongJae Park 2021-09-07  161   * has no access.  Moreover, applying the real mappings that would have many
3f49584b262cf8 SeongJae Park 2021-09-07  162   * unmapped areas inside will make the adaptive mechanism quite complex.  That
3f49584b262cf8 SeongJae Park 2021-09-07  163   * said, too huge unmapped areas inside the monitoring target should be removed
3f49584b262cf8 SeongJae Park 2021-09-07  164   * to not take the time for the adaptive mechanism.
3f49584b262cf8 SeongJae Park 2021-09-07  165   *
3f49584b262cf8 SeongJae Park 2021-09-07  166   * For the reason, we convert the complex mappings to three distinct regions
3f49584b262cf8 SeongJae Park 2021-09-07  167   * that cover every mapped area of the address space.  Also the two gaps
3f49584b262cf8 SeongJae Park 2021-09-07  168   * between the three regions are the two biggest unmapped areas in the given
3f49584b262cf8 SeongJae Park 2021-09-07  169   * address space.  In detail, this function first identifies the start and the
3f49584b262cf8 SeongJae Park 2021-09-07  170   * end of the mappings and the two biggest unmapped areas of the address space.
3f49584b262cf8 SeongJae Park 2021-09-07  171   * Then, it constructs the three regions as below:
3f49584b262cf8 SeongJae Park 2021-09-07  172   *
3f49584b262cf8 SeongJae Park 2021-09-07  173   *     [mappings[0]->start, big_two_unmapped_areas[0]->start)
3f49584b262cf8 SeongJae Park 2021-09-07  174   *     [big_two_unmapped_areas[0]->end, big_two_unmapped_areas[1]->start)
3f49584b262cf8 SeongJae Park 2021-09-07  175   *     [big_two_unmapped_areas[1]->end, mappings[nr_mappings - 1]->end)
3f49584b262cf8 SeongJae Park 2021-09-07  176   *
3f49584b262cf8 SeongJae Park 2021-09-07  177   * As usual memory map of processes is as below, the gap between the heap and
3f49584b262cf8 SeongJae Park 2021-09-07  178   * the uppermost mmap()-ed region, and the gap between the lowermost mmap()-ed
3f49584b262cf8 SeongJae Park 2021-09-07  179   * region and the stack will be two biggest unmapped regions.  Because these
3f49584b262cf8 SeongJae Park 2021-09-07  180   * gaps are exceptionally huge areas in usual address space, excluding these
3f49584b262cf8 SeongJae Park 2021-09-07  181   * two biggest unmapped regions will be sufficient to make a trade-off.
3f49584b262cf8 SeongJae Park 2021-09-07  182   *
3f49584b262cf8 SeongJae Park 2021-09-07  183   *   <heap>
3f49584b262cf8 SeongJae Park 2021-09-07  184   *   <BIG UNMAPPED REGION 1>
3f49584b262cf8 SeongJae Park 2021-09-07  185   *   <uppermost mmap()-ed region>
3f49584b262cf8 SeongJae Park 2021-09-07  186   *   (other mmap()-ed regions and small unmapped regions)
3f49584b262cf8 SeongJae Park 2021-09-07  187   *   <lowermost mmap()-ed region>
3f49584b262cf8 SeongJae Park 2021-09-07  188   *   <BIG UNMAPPED REGION 2>
3f49584b262cf8 SeongJae Park 2021-09-07  189   *   <stack>
3f49584b262cf8 SeongJae Park 2021-09-07  190   */
3f49584b262cf8 SeongJae Park 2021-09-07  191  static void __damon_va_init_regions(struct damon_ctx *ctx,
3f49584b262cf8 SeongJae Park 2021-09-07  192  				     struct damon_target *t)
3f49584b262cf8 SeongJae Park 2021-09-07  193  {
962fe7a6b1b2f9 SJ Park       2022-01-14  194  	struct damon_target *ti;
3f49584b262cf8 SeongJae Park 2021-09-07  195  	struct damon_addr_range regions[3];
442d87c7db9e9e SJ Park       2026-02-28 @196  	int tidx = 0;
3f49584b262cf8 SeongJae Park 2021-09-07  197  
3f49584b262cf8 SeongJae Park 2021-09-07  198  	if (damon_va_three_regions(t, regions)) {
962fe7a6b1b2f9 SJ Park       2022-01-14  199  		damon_for_each_target(ti, ctx) {
962fe7a6b1b2f9 SJ Park       2022-01-14  200  			if (ti == t)
962fe7a6b1b2f9 SJ Park       2022-01-14  201  				break;
962fe7a6b1b2f9 SJ Park       2022-01-14  202  			tidx++;
962fe7a6b1b2f9 SJ Park       2022-01-14  203  		}
3f49584b262cf8 SeongJae Park 2021-09-07  204  		return;
3f49584b262cf8 SeongJae Park 2021-09-07  205  	}
3f49584b262cf8 SeongJae Park 2021-09-07  206  
442d87c7db9e9e SJ Park       2026-02-28  207  	damon_set_regions(t, regions, 3, DAMON_MIN_REGION_SZ);
3f49584b262cf8 SeongJae Park 2021-09-07  208  }
3f49584b262cf8 SeongJae Park 2021-09-07  209  

:::::: The code at line 196 was first introduced by commit
:::::: 442d87c7db9e9e2a569a49d38f404b8b556b8719 mm/damon/vaddr: do not split regions for min_nr_regions

:::::: TO: SeongJae Park <sj@kernel.org>
:::::: CC: Andrew Morton <akpm@linux-foundation.org>

--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [sj:damon/next 151/151] mm/damon/vaddr.c:196:13: warning: variable 'tidx' set but not used

[SJ Park]

On Sat, 11 Jul 2026 10:36:45 +0800 kernel test robot <lkp@intel.com> wrote:

> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/sj/linux.git damon/next
> head:   b617f1f8428697a2583fb6882864224d59a91bf2
> commit: b617f1f8428697a2583fb6882864224d59a91bf2 [151/151] mm/damon/vaddr: remove debug message
> config: m68k-allyesconfig (https://download.01.org/0day-ci/archive/20260711/202607111055.NqcvApT6-lkp@intel.com/config)
> compiler: m68k-linux-gcc (GCC) 16.1.0
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260711/202607111055.NqcvApT6-lkp@intel.com/reproduce)
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202607111055.NqcvApT6-lkp@intel.com/
> 
> All warnings (new ones prefixed by >>):
> 
>    mm/damon/vaddr.c: In function '__damon_va_init_regions':
> >> mm/damon/vaddr.c:196:13: warning: variable 'tidx' set but not used [-Wunused-but-set-variable=]
>      196 |         int tidx = 0;
>          |             ^~~~

Thank you for this report.  I just pushed a fix to damon/next.


Thanks,
SJ

[...]