Hi zhaoyang.huang, 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/zhaoyang-huang/mm-skip-CMA-pages-when-they-are-not-available/20230420-163443 base: https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything patch link: https://lore.kernel.org/r/1681979577-11360-1-git-send-email-zhaoyang.huang%40unisoc.com patch subject: [PATCHv2] mm: skip CMA pages when they are not available config: powerpc-allnoconfig (https://download.01.org/0day-ci/archive/20230420/202304201725.pa3nMNWa-lkp@xxxxxxxxx/config) compiler: powerpc-linux-gcc (GCC) 12.1.0 reproduce (this is a W=1 build): wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # https://github.com/intel-lab-lkp/linux/commit/2227e95350088b79da6d6b9e6c95a67474593852 git remote add linux-review https://github.com/intel-lab-lkp/linux git fetch --no-tags linux-review zhaoyang-huang/mm-skip-CMA-pages-when-they-are-not-available/20230420-163443 git checkout 2227e95350088b79da6d6b9e6c95a67474593852 # save the config file mkdir build_dir && cp config build_dir/.config COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=powerpc olddefconfig COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=powerpc SHELL=/bin/bash If you fix the issue, kindly add following tag where applicable | Reported-by: kernel test robot <lkp@xxxxxxxxx> | Link: https://lore.kernel.org/oe-kbuild-all/202304201725.pa3nMNWa-lkp@xxxxxxxxx/ All warnings (new ones prefixed by >>): mm/vmscan.c: In function 'isolate_lru_folios': >> mm/vmscan.c:2295:22: warning: variable 'page' set but not used [-Wunused-but-set-variable] 2295 | struct page *page; | ^~~~ >> mm/vmscan.c:2294:14: warning: variable 'cma_cap' set but not used [-Wunused-but-set-variable] 2294 | bool cma_cap = true; | ^~~~~~~ vim +/page +2295 mm/vmscan.c 2261 2262 /* 2263 * Isolating page from the lruvec to fill in @dst list by nr_to_scan times. 2264 * 2265 * lruvec->lru_lock is heavily contended. Some of the functions that 2266 * shrink the lists perform better by taking out a batch of pages 2267 * and working on them outside the LRU lock. 2268 * 2269 * For pagecache intensive workloads, this function is the hottest 2270 * spot in the kernel (apart from copy_*_user functions). 2271 * 2272 * Lru_lock must be held before calling this function. 2273 * 2274 * @nr_to_scan: The number of eligible pages to look through on the list. 2275 * @lruvec: The LRU vector to pull pages from. 2276 * @dst: The temp list to put pages on to. 2277 * @nr_scanned: The number of pages that were scanned. 2278 * @sc: The scan_control struct for this reclaim session 2279 * @lru: LRU list id for isolating 2280 * 2281 * returns how many pages were moved onto *@dst. 2282 */ 2283 static unsigned long isolate_lru_folios(unsigned long nr_to_scan, 2284 struct lruvec *lruvec, struct list_head *dst, 2285 unsigned long *nr_scanned, struct scan_control *sc, 2286 enum lru_list lru) 2287 { 2288 struct list_head *src = &lruvec->lists[lru]; 2289 unsigned long nr_taken = 0; 2290 unsigned long nr_zone_taken[MAX_NR_ZONES] = { 0 }; 2291 unsigned long nr_skipped[MAX_NR_ZONES] = { 0, }; 2292 unsigned long skipped = 0; 2293 unsigned long scan, total_scan, nr_pages; > 2294 bool cma_cap = true; > 2295 struct page *page; 2296 LIST_HEAD(folios_skipped); 2297 2298 total_scan = 0; 2299 scan = 0; 2300 if ((IS_ENABLED(CONFIG_CMA)) && !current_is_kswapd() 2301 && (gfp_migratetype(sc->gfp_mask) != MIGRATE_MOVABLE)) 2302 cma_cap = false; 2303 2304 while (scan < nr_to_scan && !list_empty(src)) { 2305 struct list_head *move_to = src; 2306 struct folio *folio; 2307 2308 folio = lru_to_folio(src); 2309 prefetchw_prev_lru_folio(folio, src, flags); 2310 2311 nr_pages = folio_nr_pages(folio); 2312 total_scan += nr_pages; 2313 2314 page = &folio->page; 2315 2316 if ((folio_zonenum(folio) > sc->reclaim_idx) 2317 #ifdef CONFIG_CMA 2318 || (get_pageblock_migratetype(page) == MIGRATE_CMA && !cma_cap) 2319 #endif 2320 ) { 2321 nr_skipped[folio_zonenum(folio)] += nr_pages; 2322 move_to = &folios_skipped; 2323 goto move; 2324 } 2325 /* 2326 * Do not count skipped folios because that makes the function 2327 * return with no isolated folios if the LRU mostly contains 2328 * ineligible folios. This causes the VM to not reclaim any 2329 * folios, triggering a premature OOM. 2330 * Account all pages in a folio. 2331 */ 2332 scan += nr_pages; 2333 2334 if (!folio_test_lru(folio)) 2335 goto move; 2336 if (!sc->may_unmap && folio_mapped(folio)) 2337 goto move; 2338 2339 /* 2340 * Be careful not to clear the lru flag until after we're 2341 * sure the folio is not being freed elsewhere -- the 2342 * folio release code relies on it. 2343 */ 2344 if (unlikely(!folio_try_get(folio))) 2345 goto move; 2346 2347 if (!folio_test_clear_lru(folio)) { 2348 /* Another thread is already isolating this folio */ 2349 folio_put(folio); 2350 goto move; 2351 } 2352 2353 nr_taken += nr_pages; 2354 nr_zone_taken[folio_zonenum(folio)] += nr_pages; 2355 move_to = dst; 2356 move: 2357 list_move(&folio->lru, move_to); 2358 } 2359 2360 /* 2361 * Splice any skipped folios to the start of the LRU list. Note that 2362 * this disrupts the LRU order when reclaiming for lower zones but 2363 * we cannot splice to the tail. If we did then the SWAP_CLUSTER_MAX 2364 * scanning would soon rescan the same folios to skip and waste lots 2365 * of cpu cycles. 2366 */ 2367 if (!list_empty(&folios_skipped)) { 2368 int zid; 2369 2370 list_splice(&folios_skipped, src); 2371 for (zid = 0; zid < MAX_NR_ZONES; zid++) { 2372 if (!nr_skipped[zid]) 2373 continue; 2374 2375 __count_zid_vm_events(PGSCAN_SKIP, zid, nr_skipped[zid]); 2376 skipped += nr_skipped[zid]; 2377 } 2378 } 2379 *nr_scanned = total_scan; 2380 trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, nr_to_scan, 2381 total_scan, skipped, nr_taken, 2382 sc->may_unmap ? 0 : ISOLATE_UNMAPPED, lru); 2383 update_lru_sizes(lruvec, lru, nr_zone_taken); 2384 return nr_taken; 2385 } 2386 -- 0-DAY CI Kernel Test Service https://github.com/intel/lkp-tests
