Re: [RFC PATCH 2/4] mm: kpromoted: Hot page info collection and promotion daemon

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

Hi Bharata,

[This is a private test report for your RFC patch.]
kernel test robot noticed the following build warnings:

[auto build test WARNING on tip/x86/core]
[also build test WARNING on tip/x86/mm linus/master v6.14-rc5]
[cannot apply to akpm-mm/mm-everything next-20250306]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Bharata-B-Rao/mm-migrate-Allow-misplaced-migration-without-VMA-too/20250306-134949
base:   tip/x86/core
patch link:    https://lore.kernel.org/r/20250306054532.221138-3-bharata%40amd.com
patch subject: [RFC PATCH 2/4] mm: kpromoted: Hot page info collection and promotion daemon
config: s390-randconfig-001-20250307 (https://download.01.org/0day-ci/archive/20250307/202503071523.f89emNyA-lkp@intel.com/config)
compiler: s390-linux-gcc (GCC) 14.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250307/202503071523.f89emNyA-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/202503071523.f89emNyA-lkp@intel.com/

All warnings (new ones prefixed by >>):

   mm/kpromoted.c: In function 'kpromoted_record_access':
>> mm/kpromoted.c:158:13: warning: variable 'ret' set but not used [-Wunused-but-set-variable]
     158 |         int ret, bkt;
         |             ^~~


vim +/ret +158 mm/kpromoted.c

   147	
   148	/*
   149	 * Called by subsystems that generate page hotness/access information.
   150	 *
   151	 * Records the memory access info for futher action by kpromoted.
   152	 */
   153	int kpromoted_record_access(u64 pfn, int nid, int src, unsigned long now)
   154	{
   155		struct page_hotness_info *phi;
   156		struct page *page;
   157		struct folio *folio;
 > 158		int ret, bkt;
   159	
   160		count_vm_event(KPROMOTED_RECORDED_ACCESSES);
   161	
   162		switch (src) {
   163		case KPROMOTED_HW_HINTS:
   164			count_vm_event(KPROMOTED_RECORD_HWHINTS);
   165			break;
   166		case KPROMOTED_PGTABLE_SCAN:
   167			count_vm_event(KPROMOTED_RECORD_PGTSCANS);
   168			break;
   169		default:
   170			break;
   171		}
   172	
   173		/*
   174		 * Record only accesses from lower tiers.
   175		 * Assuming node having CPUs as toptier for now.
   176		 */
   177		if (node_is_toptier(pfn_to_nid(pfn))) {
   178			count_vm_event(KPROMOTED_RECORD_TOPTIER);
   179			return 0;
   180		}
   181	
   182		page = pfn_to_online_page(pfn);
   183		if (!page || is_zone_device_page(page))
   184			return 0;
   185	
   186		folio = page_folio(page);
   187		if (!folio_test_lru(folio))
   188			return 0;
   189	
   190		bkt = hash_min(pfn, KPROMOTED_HASH_ORDER);
   191		mutex_lock(&page_hotness_lock[bkt]);
   192		phi = kpromoted_lookup(pfn, bkt, now);
   193		if (!phi) {
   194			ret = PTR_ERR(phi);
   195			goto out;
   196		}
   197	
   198		if ((phi->last_update - now) > msecs_to_jiffies(KPROMOTED_FREQ_WINDOW)) {
   199			/* New window */
   200			phi->frequency = 1; /* TODO: Factor in the history */
   201			phi->last_update = now;
   202		} else {
   203			phi->frequency++;
   204		}
   205		phi->recency = now;
   206	
   207		/*
   208		 * TODOs:
   209		 * 1. Source nid is hard-coded for some temperature sources
   210		 * 2. Take action if hot_node changes - may be a shared page?
   211		 * 3. Maintain node info for every access within the window?
   212		 */
   213		phi->hot_node = (nid == NUMA_NO_NODE) ? 1 : nid;
   214		mutex_unlock(&page_hotness_lock[bkt]);
   215	out:
   216		return 0;
   217	}
   218	

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