Re: [PATCH] mm: compaction: skip memory compaction when there are not enough migratable pages

[kernel test robot <lkp@intel.com>]

Hi,

kernel test robot noticed the following build warnings:

[auto build test WARNING on akpm-mm/mm-everything]

url:    https://github.com/intel-lab-lkp/linux/commits/yangge1116-126-com/mm-compaction-skip-memory-compaction-when-there-are-not-enough-migratable-pages/20250104-170112
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/1735981122-2085-1-git-send-email-yangge1116%40126.com
patch subject: [PATCH] mm: compaction: skip memory compaction when there are not enough migratable pages
config: i386-buildonly-randconfig-001-20250104 (https://download.01.org/0day-ci/archive/20250104/202501041908.jDpLhAgL-lkp@intel.com/config)
compiler: clang version 19.1.3 (https://github.com/llvm/llvm-project ab51eccf88f5321e7c60591c5546b254b6afab99)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250104/202501041908.jDpLhAgL-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/202501041908.jDpLhAgL-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from mm/compaction.c:15:
   include/linux/mm_inline.h:47:41: warning: arithmetic between different enumeration types ('enum node_stat_item' and 'enum lru_list') [-Wenum-enum-conversion]
      47 |         __mod_lruvec_state(lruvec, NR_LRU_BASE + lru, nr_pages);
         |                                    ~~~~~~~~~~~ ^ ~~~
   include/linux/mm_inline.h:49:22: warning: arithmetic between different enumeration types ('enum zone_stat_item' and 'enum lru_list') [-Wenum-enum-conversion]
      49 |                                 NR_ZONE_LRU_BASE + lru, nr_pages);
         |                                 ~~~~~~~~~~~~~~~~ ^ ~~~
>> mm/compaction.c:2386:13: warning: unused variable 'pgdat' [-Wunused-variable]
    2386 |         pg_data_t *pgdat = zone->zone_pgdat;
         |                    ^~~~~
   3 warnings generated.


vim +/pgdat +2386 mm/compaction.c

  2381	
  2382	static bool __compaction_suitable(struct zone *zone, int order,
  2383					  int highest_zoneidx,
  2384					  unsigned long wmark_target)
  2385	{
> 2386		pg_data_t *pgdat = zone->zone_pgdat;
  2387		unsigned long sum, nr_pinned;
  2388		unsigned long watermark;
  2389	
  2390		sum = node_page_state(pgdat, NR_INACTIVE_FILE) +
  2391			node_page_state(pgdat, NR_INACTIVE_ANON) +
  2392			node_page_state(pgdat, NR_ACTIVE_FILE) +
  2393			node_page_state(pgdat, NR_ACTIVE_ANON);
  2394	
  2395		nr_pinned = node_page_state(pgdat, NR_FOLL_PIN_ACQUIRED) -
  2396			node_page_state(pgdat, NR_FOLL_PIN_RELEASED);
  2397	
  2398		/*
  2399		 * Gup-pinned pages are non-migratable. After subtracting these pages,
  2400		 * we need to check if the remaining pages are sufficient for memory
  2401		 * compaction.
  2402		 */
  2403		if ((sum - nr_pinned) < (1 << order))
  2404			return false;
  2405	
  2406		/*
  2407		 * Watermarks for order-0 must be met for compaction to be able to
  2408		 * isolate free pages for migration targets. This means that the
  2409		 * watermark and alloc_flags have to match, or be more pessimistic than
  2410		 * the check in __isolate_free_page(). We don't use the direct
  2411		 * compactor's alloc_flags, as they are not relevant for freepage
  2412		 * isolation. We however do use the direct compactor's highest_zoneidx
  2413		 * to skip over zones where lowmem reserves would prevent allocation
  2414		 * even if compaction succeeds.
  2415		 * For costly orders, we require low watermark instead of min for
  2416		 * compaction to proceed to increase its chances.
  2417		 * ALLOC_CMA is used, as pages in CMA pageblocks are considered
  2418		 * suitable migration targets
  2419		 */
  2420		watermark = (order > PAGE_ALLOC_COSTLY_ORDER) ?
  2421					low_wmark_pages(zone) : min_wmark_pages(zone);
  2422		watermark += compact_gap(order);
  2423		return __zone_watermark_ok(zone, 0, watermark, highest_zoneidx,
  2424					   ALLOC_CMA, wmark_target);
  2425	}
  2426	

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