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Date: Fri, 13 Jun 2014 08:52:22 +0400
From: Konstantin Khlebnikov <koct9i@...il.com>
To: Chen Yucong <slaoub@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Mel Gorman <mgorman@...e.de>,
Johannes Weiner <hannes@...xchg.org>, mhocko@...e.cz,
Rik van Riel <riel@...hat.com>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] mm/vmscan.c: wrap five parameters into shrink_result
for reducing the stack consumption
On Fri, Jun 13, 2014 at 8:36 AM, Chen Yucong <slaoub@...il.com> 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 shrink_result and removes
> some temporary variables, thus making the relative functions to consume fewer
> stack space.
I think it's better to put them into struct scan_control.
Reset them before calling shrinker or take a snapshot to get delta.
>
> 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 <slaoub@...il.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
>
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