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#author("2025-09-11T20:14:20+09:00","default:guest","guest") #author("2025-09-11T20:14:40+09:00","default:guest","guest") *参照元 [#w4116c8e] #backlinks *説明 [#e45b90b4] -パス: [[linux-5.15/mm/vmscan.c]] -FIXME: これは何？ --説明 **引数 [#ncde76d3] -unsigned long nr_to_scan -- -struct lruvec *lruvec -- --[[linux-5.15/lruvec]] -struct list_head *dst -- --[[linux-5.15/list_head]] -unsigned long *nr_scanned -- -struct scan_control *sc -- --[[linux-5.15/scan_control]] -enum lru_list lru -- --[[linux-5.15/lru_list]] **返り値 [#g28b4382] - -unsigned long -- **参考 [#cf2e02fa] *実装 [#t08d6a17] /* * Isolating page from the lruvec to fill in @dst list by nr_to_scan times. * * lruvec->lru_lock is heavily contended. Some of the functions that * shrink the lists perform better by taking out a batch of pages * and working on them outside the LRU lock. * * For pagecache intensive workloads, this function is the hottest * spot in the kernel (apart from copy_*_user functions). * * Lru_lock must be held before calling this function. * * @nr_to_scan: The number of eligible pages to look through on the list. * @lruvec: The LRU vector to pull pages from. * @dst: The temp list to put pages on to. * @nr_scanned: The number of pages that were scanned. * @sc: The scan_control struct for this reclaim session * @lru: LRU list id for isolating * * returns how many pages were moved onto *@dst. */ static unsigned long isolate_lru_pages(unsigned long nr_to_scan, struct lruvec *lruvec, struct list_head *dst, unsigned long *nr_scanned, struct scan_control *sc, enum lru_list lru) { struct list_head *src = &lruvec->lists[lru]; unsigned long nr_taken = 0; unsigned long nr_zone_taken[MAX_NR_ZONES] = { 0 }; unsigned long nr_skipped[MAX_NR_ZONES] = { 0, }; unsigned long skipped = 0; unsigned long scan, total_scan, nr_pages; LIST_HEAD(pages_skipped); isolate_mode_t mode = (sc->may_unmap ? 0 : ISOLATE_UNMAPPED); - --[[linux-5.15/list_head]] --[[linux-5.15/LIST_HEAD()]] total_scan = 0; scan = 0; while (scan < nr_to_scan && !list_empty(src)) { struct page *page; page = lru_to_page(src); prefetchw_prev_lru_page(page, src, flags); nr_pages = compound_nr(page); total_scan += nr_pages; if (page_zonenum(page) > sc->reclaim_idx) { list_move(&page->lru, &pages_skipped); nr_skipped[page_zonenum(page)] += nr_pages; continue; } - --[[linux-5.15/list_empty()]] --[[linux-5.15/lru_to_page()]] --[[linux-5.15/prefetchw_prev_lru_page()]] --[[linux-5.15/page_zonenum()]] --[[linux-5.15/list_move()]] /* * Do not count skipped pages because that makes the function * return with no isolated pages if the LRU mostly contains * ineligible pages. This causes the VM to not reclaim any * pages, triggering a premature OOM. * * Account all tail pages of THP. This would not cause * premature OOM since __isolate_lru_page() returns -EBUSY * only when the page is being freed somewhere else. */ scan += nr_pages; if (!__isolate_lru_page_prepare(page, mode)) { /* It is being freed elsewhere */ list_move(&page->lru, src); continue; } - --[[linux-5.15/isolate_lru_page_prepare()]] --[[linux-5.15/list_move()]] /* * Be careful not to clear PageLRU until after we're * sure the page is not being freed elsewhere -- the * page release code relies on it. */ if (unlikely(!get_page_unless_zero(page))) { list_move(&page->lru, src); continue; } - --[[linux-5.15/unlikely()]] --[[linux-5.15/get_page_unless_zero()]] --[[linux-5.15/list_move()]] if (!TestClearPageLRU(page)) { /* Another thread is already isolating this page */ put_page(page); list_move(&page->lru, src); continue; } - --[[linux-5.15/TestClearPageLRU()]] --[[linux-5.15/put_page()]] --[[linux-5.15/list_move()]] nr_taken += nr_pages; nr_zone_taken[page_zonenum(page)] += nr_pages; list_move(&page->lru, dst); } - --[[linux-5.15/list_move()]] /* * Splice any skipped pages to the start of the LRU list. Note that * this disrupts the LRU order when reclaiming for lower zones but * we cannot splice to the tail. If we did then the SWAP_CLUSTER_MAX * scanning would soon rescan the same pages to skip and put the * system at risk of premature OOM. */ if (!list_empty(&pages_skipped)) { int zid; list_splice(&pages_skipped, src); for (zid = 0; zid < MAX_NR_ZONES; zid++) { if (!nr_skipped[zid]) continue; __count_zid_vm_events(PGSCAN_SKIP, zid, nr_skipped[zid]); skipped += nr_skipped[zid]; } } *nr_scanned = total_scan; trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, nr_to_scan, total_scan, skipped, nr_taken, mode, lru); update_lru_sizes(lruvec, lru, nr_zone_taken); return nr_taken; } - --[[linux-5.15/list_empty()]] --[[linux-5.15/list_splice()]] --[[linux-5.15/__count_zid_vm_events()]] --[[linux-5.15/trace_mm_vmscan_lru_isolate()]] --[[linux-5.15/update_lru_sizes()]] *コメント [#r2c53b57]
