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Date: Thu, 12 Jun 2014 08:45:39 -0400
From: Rik van Riel <riel@...hat.com>
To: Chen Yucong <slaoub@...il.com>, akpm@...ux-foundation.org
CC: mgorman@...e.de, hannes@...xchg.org, mhocko@...e.cz,
linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/vmscan.c: wrap five parameters into arg_container
in shrink_page_list()
On 06/12/2014 05:36 AM, Chen Yucong wrote:
> 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 arg_container and removes some temporary
> variables, thus making shrink_page_list() to consume fewer stack space.
Won't the container with those arguments now live on the stack,
using up the same space that the variables used to take?
> Before mm/vmscan.c is modified:
> 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
>
> Signed-off-by: Chen Yucong <slaoub@...il.com>
> ---
> mm/vmscan.c | 64 +++++++++++++++++++++++++++--------------------------------
> 1 file changed, 29 insertions(+), 35 deletions(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index a8ffe4e..538cdcf 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -790,6 +790,14 @@ static void page_check_dirty_writeback(struct page *page,
> mapping->a_ops->is_dirty_writeback(page, dirty, writeback);
> }
>
> +struct arg_container {
> + 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
> */
> @@ -797,22 +805,13 @@ 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 arg_container *ac,
> 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 +857,10 @@ static unsigned long shrink_page_list(struct list_head *page_list,
> */
> page_check_dirty_writeback(page, &dirty, &writeback);
> if (dirty || writeback)
> - nr_dirty++;
> + ac->nr_dirty++;
>
> if (dirty && !writeback)
> - nr_unqueued_dirty++;
> + ac->nr_unqueued_dirty++;
>
> /*
> * Treat this page as congested if the underlying BDI is or if
> @@ -872,7 +871,7 @@ 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++;
> + ac->nr_congested++;
>
> /*
> * If a page at the tail of the LRU is under writeback, there
> @@ -916,7 +915,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
> if (current_is_kswapd() &&
> PageReclaim(page) &&
> zone_is_reclaim_writeback(zone)) {
> - nr_immediate++;
> + ac->nr_immediate++;
> goto keep_locked;
>
> /* Case 2 above */
> @@ -934,7 +933,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
> * and it's also appropriate in global reclaim.
> */
> SetPageReclaim(page);
> - nr_writeback++;
> + ac->nr_writeback++;
>
> goto keep_locked;
>
> @@ -1132,11 +1131,6 @@ 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 +1142,8 @@ 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 arg_container dummy;
> struct page *page, *next;
> LIST_HEAD(clean_pages);
>
> @@ -1161,8 +1156,7 @@ 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 +1463,13 @@ 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 arg_container ac = {
> + .nr_dirty = 0,
> + .nr_congested = 0,
> + .nr_unqueued_dirty = 0,
> + .nr_writeback = 0,
> + .nr_immediate = 0,
> + };
> isolate_mode_t isolate_mode = 0;
> int file = is_file_lru(lru);
> struct zone *zone = lruvec_zone(lruvec);
> @@ -1515,9 +1511,7 @@ 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);
> + &ac, false);
>
> spin_lock_irq(&zone->lru_lock);
>
> @@ -1554,7 +1548,7 @@ 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 (ac.nr_writeback && ac.nr_writeback == nr_taken)
> zone_set_flag(zone, ZONE_WRITEBACK);
>
> /*
> @@ -1566,7 +1560,7 @@ 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 (ac.nr_dirty && ac.nr_dirty == ac.nr_congested)
> zone_set_flag(zone, ZONE_CONGESTED);
>
> /*
> @@ -1576,7 +1570,7 @@ 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 (ac.nr_unqueued_dirty == nr_taken)
> zone_set_flag(zone, ZONE_TAIL_LRU_DIRTY);
>
> /*
> @@ -1585,7 +1579,7 @@ 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 ((ac.nr_unqueued_dirty == nr_taken || ac.nr_immediate) &&
> current_may_throttle())
> congestion_wait(BLK_RW_ASYNC, HZ/10);
> }
>
--
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