shrink_page_list() has too many arguments that have already reached ten. Some of those arguments and temporary variables introduces extra 80 bytes on the stack. This patch wraps five parameters into shrink_result and removes some temporary variables, thus making the relative functions to consume fewer stack space.
Before mm/vmscan.c is changed: text data bss dec hex filename 6876698 957224 966656 8800578 864942 vmlinux-3.15 After mm/vmscan.c is changed: text data bss dec hex filename 6876506 957224 966656 8800386 864882 vmlinux-3.15 scripts/checkstack.pl can be used for checking the change of the target function stack. Before mm/vmscan.c is changed: 0xffffffff810af103 shrink_inactive_list []: 152 0xffffffff810af43d shrink_inactive_list []: 152 ------------------------------------------------------------- 0xffffffff810aede8 reclaim_clean_pages_from_list []: 184 0xffffffff810aeef8 reclaim_clean_pages_from_list []: 184 ------------------------------------------------------------- 0xffffffff810ae582 shrink_page_list []: 232 0xffffffff810aedb5 shrink_page_list []: 232 After mm/vmscan.c is changed:: 0xffffffff810af078 shrink_inactive_list []: 120 0xffffffff810af36d shrink_inactive_list []: 120 ------------------------------------------------------------- 0xffffffff810aed6c reclaim_clean_pages_from_list []: 152 0xffffffff810aee68 reclaim_clean_pages_from_list []: 152 -------------------------------------------------------------------------------------- 0xffffffff810ae586 shrink_page_list []: 184 ---> sub $0xb8,%rsp 0xffffffff810aed36 shrink_page_list []: 184 ---> add $0xb8,%rsp Via the above figures, we can find that the difference value of the stack is 32 for shrink_inactive_list and reclaim_clean_pages_from_list, and this value is 48(232-184) for shrink_page_list. From the hierarchy of functions called, the total difference value is 80(32+48) for this change. Changes since v1: https://lkml.org/lkml/2014/6/12/159 * Rename arg_container to shrink_result * Change the the way of initializing shrink_result object. Signed-off-by: Chen Yucong <sla...@gmail.com> --- mm/vmscan.c | 62 ++++++++++++++++++++++++++--------------------------------- 1 file changed, 27 insertions(+), 35 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index a8ffe4e..3f28e39 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -791,28 +791,31 @@ static void page_check_dirty_writeback(struct page *page, } /* + * Callers pass a prezeroed shrink_result into the shrink functions to gather + * statistics about how many pages of particular states were processed + */ +struct shrink_result { + unsigned long nr_dirty; + unsigned long nr_unqueued_dirty; + unsigned long nr_congested; + unsigned long nr_writeback; + unsigned long nr_immediate; +}; + +/* * shrink_page_list() returns the number of reclaimed pages */ static unsigned long shrink_page_list(struct list_head *page_list, struct zone *zone, struct scan_control *sc, enum ttu_flags ttu_flags, - unsigned long *ret_nr_dirty, - unsigned long *ret_nr_unqueued_dirty, - unsigned long *ret_nr_congested, - unsigned long *ret_nr_writeback, - unsigned long *ret_nr_immediate, + struct shrink_result *sr, bool force_reclaim) { LIST_HEAD(ret_pages); LIST_HEAD(free_pages); int pgactivate = 0; - unsigned long nr_unqueued_dirty = 0; - unsigned long nr_dirty = 0; - unsigned long nr_congested = 0; unsigned long nr_reclaimed = 0; - unsigned long nr_writeback = 0; - unsigned long nr_immediate = 0; cond_resched(); @@ -858,10 +861,10 @@ static unsigned long shrink_page_list(struct list_head *page_list, */ page_check_dirty_writeback(page, &dirty, &writeback); if (dirty || writeback) - nr_dirty++; + sr->nr_dirty++; if (dirty && !writeback) - nr_unqueued_dirty++; + sr->nr_unqueued_dirty++; /* * Treat this page as congested if the underlying BDI is or if @@ -872,7 +875,7 @@ static unsigned long shrink_page_list(struct list_head *page_list, mapping = page_mapping(page); if ((mapping && bdi_write_congested(mapping->backing_dev_info)) || (writeback && PageReclaim(page))) - nr_congested++; + sr->nr_congested++; /* * If a page at the tail of the LRU is under writeback, there @@ -916,7 +919,7 @@ static unsigned long shrink_page_list(struct list_head *page_list, if (current_is_kswapd() && PageReclaim(page) && zone_is_reclaim_writeback(zone)) { - nr_immediate++; + sr->nr_immediate++; goto keep_locked; /* Case 2 above */ @@ -934,7 +937,7 @@ static unsigned long shrink_page_list(struct list_head *page_list, * and it's also appropriate in global reclaim. */ SetPageReclaim(page); - nr_writeback++; + sr->nr_writeback++; goto keep_locked; @@ -1132,11 +1135,6 @@ keep: list_splice(&ret_pages, page_list); count_vm_events(PGACTIVATE, pgactivate); mem_cgroup_uncharge_end(); - *ret_nr_dirty += nr_dirty; - *ret_nr_congested += nr_congested; - *ret_nr_unqueued_dirty += nr_unqueued_dirty; - *ret_nr_writeback += nr_writeback; - *ret_nr_immediate += nr_immediate; return nr_reclaimed; } @@ -1148,7 +1146,8 @@ unsigned long reclaim_clean_pages_from_list(struct zone *zone, .priority = DEF_PRIORITY, .may_unmap = 1, }; - unsigned long ret, dummy1, dummy2, dummy3, dummy4, dummy5; + unsigned long ret; + struct shrink_result dummy = { }; struct page *page, *next; LIST_HEAD(clean_pages); @@ -1161,8 +1160,7 @@ unsigned long reclaim_clean_pages_from_list(struct zone *zone, } ret = shrink_page_list(&clean_pages, zone, &sc, - TTU_UNMAP|TTU_IGNORE_ACCESS, - &dummy1, &dummy2, &dummy3, &dummy4, &dummy5, true); + TTU_UNMAP|TTU_IGNORE_ACCESS, &dummy, true); list_splice(&clean_pages, page_list); mod_zone_page_state(zone, NR_ISOLATED_FILE, -ret); return ret; @@ -1469,11 +1467,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec, unsigned long nr_scanned; unsigned long nr_reclaimed = 0; unsigned long nr_taken; - unsigned long nr_dirty = 0; - unsigned long nr_congested = 0; - unsigned long nr_unqueued_dirty = 0; - unsigned long nr_writeback = 0; - unsigned long nr_immediate = 0; + struct shrink_result sr = { }; isolate_mode_t isolate_mode = 0; int file = is_file_lru(lru); struct zone *zone = lruvec_zone(lruvec); @@ -1515,9 +1509,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec, return 0; nr_reclaimed = shrink_page_list(&page_list, zone, sc, TTU_UNMAP, - &nr_dirty, &nr_unqueued_dirty, &nr_congested, - &nr_writeback, &nr_immediate, - false); + &sr, false); spin_lock_irq(&zone->lru_lock); @@ -1554,7 +1546,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec, * of pages under pages flagged for immediate reclaim and stall if any * are encountered in the nr_immediate check below. */ - if (nr_writeback && nr_writeback == nr_taken) + if (sr.nr_writeback && sr.nr_writeback == nr_taken) zone_set_flag(zone, ZONE_WRITEBACK); /* @@ -1566,7 +1558,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec, * Tag a zone as congested if all the dirty pages scanned were * backed by a congested BDI and wait_iff_congested will stall. */ - if (nr_dirty && nr_dirty == nr_congested) + if (sr.nr_dirty && sr.nr_dirty == sr.nr_congested) zone_set_flag(zone, ZONE_CONGESTED); /* @@ -1576,7 +1568,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec, * pages from reclaim context. It will forcibly stall in the * next check. */ - if (nr_unqueued_dirty == nr_taken) + if (sr.nr_unqueued_dirty == nr_taken) zone_set_flag(zone, ZONE_TAIL_LRU_DIRTY); /* @@ -1585,7 +1577,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec, * implies that pages are cycling through the LRU faster than * they are written so also forcibly stall. */ - if ((nr_unqueued_dirty == nr_taken || nr_immediate) && + if ((sr.nr_unqueued_dirty == nr_taken || sr.nr_immediate) && current_may_throttle()) congestion_wait(BLK_RW_ASYNC, HZ/10); } -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
