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Date: Fri, 2 Mar 2012 15:18:47 +0800
From: Fengguang Wu <fengguang.wu@...el.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Greg Thelen <gthelen@...gle.com>, Jan Kara <jack@...e.cz>,
Ying Han <yinghan@...gle.com>,
"hannes@...xchg.org" <hannes@...xchg.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
Rik van Riel <riel@...hat.com>,
Linux Memory Management List <linux-mm@...ck.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH] mm: don't treat anonymous pages as dirtyable pages
The test results:
With the below heavy memory usage and one file copy from sparse file
to USB key under way,
root@snb /home/wfg/memcg-dirty/snb# free
total used free shared buffers cached
Mem: 6801 6750 50 0 0 893
-/+ buffers/cache: 5857 944
Swap: 51106 34 51072
There are no single reclaim waits:
/debug/vm/nr_reclaim_throttle_clean:0
/debug/vm/nr_reclaim_throttle_kswapd:0
/debug/vm/nr_reclaim_throttle_recent_write:0
/debug/vm/nr_reclaim_throttle_write:0
/debug/vm/nr_reclaim_wait_congested:0
/debug/vm/nr_reclaim_wait_writeback:0
/debug/vm/nr_migrate_wait_writeback:0
and only occasionally increase of
/debug/vm/nr_congestion_wait (from kswapd)
nr_vmscan_write
allocstall
And the most visible thing: windows switching remains swiftly fast:
time window title
-----------------------------------------------------------------------------
3024.91 A LibreOffice 3.4
3024.97 A Restore Session - Iceweasel
3024.98 A System Settings
3025.13 A urxvt
3025.14 A xeyes
3025.15 A snb:/home/wfg - ZSH
3025.16 A snb:/home/wfg - ZSH
3025.17 A Xpdf: /usr/share/doc/shared-mime-info/shared-mime-info-spec.pdf
3025.18 A OpenOffice.org
3025.23 A OpenOffice.org
3025.25 A OpenOffice.org
3025.26 A OpenOffice.org
3025.27 A OpenOffice.org
3025.28 A Chess
3025.29 A Dictionary
3025.31 A System Monitor
3025.35 A snb:/home/wfg - ZSH
3025.41 A Desktop Help
3025.43 A Mines
3025.49 A Tetravex
3025.54 A Iagno
3025.55 A Four-in-a-row
3025.60 A Mahjongg - Easy
3025.64 A Klotski
3025.66 A Five or More
3025.68 A Tali
3025.69 A Robots
3025.71 A Klondike
3025.79 A Home
3025.82 A Home
3025.86 A *Unsaved Document 1 - gedit
3025.87 A Sudoku
3025.93 A LibreOffice 3.4
3025.98 A Restore Session - Iceweasel
3025.99 A System Settings
3026.13 A urxvt
Thanks,
Fengguang
> Assume a mem=1GB desktop (swap enabled) with 800MB anonymous pages and
> 200MB file pages. When the user starts a heavy dirtier task, the file
> LRU lists may be mostly filled with dirty pages since the global dirty
> limit is calculated as
>
> (anon+file) * 20% = 1GB * 20% = 200MB
>
> This makes the file LRU lists hard to reclaim, which in turn increases
> the scan rate of the anon LRU lists and lead to a lot of swapping. This
> is probably one big reason why some desktop users see bad responsiveness
> during heavy file copies once the swap is enabled.
>
> The heavy swapping could mostly be avoided by calculating the global
> dirty limit as
>
> file * 20% = 200MB * 20% = 40MB
>
> The side effect would be that users feel longer file copy time because
> the copy task is throttled earlier than before. However typical users
> should be much more sensible to interactive performance rather than the
> copy task which may well be leaved in the background.
>
> Signed-off-by: Fengguang Wu <fengguang.wu@...el.com>
> ---
> include/linux/vmstat.h | 1 -
> mm/page-writeback.c | 10 ++++++----
> mm/vmscan.c | 14 --------------
> 3 files changed, 6 insertions(+), 19 deletions(-)
>
> --- linux.orig/include/linux/vmstat.h 2012-03-02 13:55:28.569749568 +0800
> +++ linux/include/linux/vmstat.h 2012-03-02 13:56:06.585750471 +0800
> @@ -139,7 +139,6 @@ static inline unsigned long zone_page_st
> return x;
> }
>
> -extern unsigned long global_reclaimable_pages(void);
> extern unsigned long zone_reclaimable_pages(struct zone *zone);
>
> #ifdef CONFIG_NUMA
> --- linux.orig/mm/page-writeback.c 2012-03-02 13:55:28.549749567 +0800
> +++ linux/mm/page-writeback.c 2012-03-02 13:56:26.257750938 +0800
> @@ -181,8 +181,7 @@ static unsigned long highmem_dirtyable_m
> struct zone *z =
> &NODE_DATA(node)->node_zones[ZONE_HIGHMEM];
>
> - x += zone_page_state(z, NR_FREE_PAGES) +
> - zone_reclaimable_pages(z) - z->dirty_balance_reserve;
> + x += zone_dirtyable_memory(z);
> }
> /*
> * Make sure that the number of highmem pages is never larger
> @@ -206,7 +205,9 @@ unsigned long global_dirtyable_memory(vo
> {
> unsigned long x;
>
> - x = global_page_state(NR_FREE_PAGES) + global_reclaimable_pages() -
> + x = global_page_state(NR_FREE_PAGES) +
> + global_page_state(NR_ACTIVE_FILE) +
> + global_page_state(NR_INACTIVE_FILE) -
> dirty_balance_reserve;
>
> if (!vm_highmem_is_dirtyable)
> @@ -275,7 +276,8 @@ unsigned long zone_dirtyable_memory(stru
> * care about vm_highmem_is_dirtyable here.
> */
> return zone_page_state(zone, NR_FREE_PAGES) +
> - zone_reclaimable_pages(zone) -
> + zone_page_state(zone, NR_ACTIVE_FILE) +
> + zone_page_state(zone, NR_INACTIVE_FILE) -
> zone->dirty_balance_reserve;
> }
>
> --- linux.orig/mm/vmscan.c 2012-03-02 13:55:28.561749567 +0800
> +++ linux/mm/vmscan.c 2012-03-02 13:56:06.585750471 +0800
> @@ -3315,20 +3315,6 @@ void wakeup_kswapd(struct zone *zone, in
> * - mapped pages, which may require several travels to be reclaimed
> * - dirty pages, which is not "instantly" reclaimable
> */
> -unsigned long global_reclaimable_pages(void)
> -{
> - int nr;
> -
> - nr = global_page_state(NR_ACTIVE_FILE) +
> - global_page_state(NR_INACTIVE_FILE);
> -
> - if (nr_swap_pages > 0)
> - nr += global_page_state(NR_ACTIVE_ANON) +
> - global_page_state(NR_INACTIVE_ANON);
> -
> - return nr;
> -}
> -
> unsigned long zone_reclaimable_pages(struct zone *zone)
> {
> int nr;
--
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