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Date: Thu, 4 Dec 2008 13:20:21 +0900
From: "MinChan Kim" <minchan.kim@...il.com>
To: "KOSAKI Motohiro" <kosaki.motohiro@...fujitsu.com>
Cc: "Rik van Riel" <riel@...hat.com>, akpm@...ux-foundation.org,
linux-mm@...ck.org, linux-kernel@...r.kernel.org, mel@....ul.ie
Subject: Re: [PATCH] vmscan: improve reclaim throuput to bail out patch take2
Hi, Kosaki-san.
It's a great improvement with only one variable than I expected. :)
What is your test environment ? (CPU, L1, L2 cache size and so )
Just out of curiosity.
On Thu, Dec 4, 2008 at 10:28 AM, KOSAKI Motohiro
<kosaki.motohiro@...fujitsu.com> wrote:
> The vmscan bail out patch move nr_reclaimed variable to struct scan_control.
> Unfortunately, indirect access can easily happen cache miss.
>
> if heavy memory pressure happend, that's ok.
> cache miss already plenty. it is not observable.
>
> but, if memory pressure is lite, performance degression is obserbable.
>
>
> I compared following three pattern (it was mesured 10 times each)
>
> hackbench 125 process 3000
> hackbench 130 process 3000
> hackbench 135 process 3000
>
> 2.6.28-rc6 bail-out
>
> 125 130 135 125 130 135
> ==============================================================
> 71.866 75.86 81.274 93.414 73.254 193.382
> 74.145 78.295 77.27 74.897 75.021 80.17
> 70.305 77.643 75.855 70.134 77.571 79.896
> 74.288 73.986 75.955 77.222 78.48 80.619
> 72.029 79.947 78.312 75.128 82.172 79.708
> 71.499 77.615 77.042 74.177 76.532 77.306
> 76.188 74.471 83.562 73.839 72.43 79.833
> 73.236 75.606 78.743 76.001 76.557 82.726
> 69.427 77.271 76.691 76.236 79.371 103.189
> 72.473 76.978 80.643 69.128 78.932 75.736
>
> avg 72.545 76.767 78.534 76.017 77.03 93.256
> std 1.89 1.71 2.41 6.29 2.79 34.16
> min 69.427 73.986 75.855 69.128 72.43 75.736
> max 76.188 79.947 83.562 93.414 82.172 193.382
>
>
> about 4-5% degression.
>
> Then, this patch introduce temporal local variable.
>
> result:
>
> 2.6.28-rc6 this patch
>
> num 125 130 135 125 130 135
> ==============================================================
> 71.866 75.86 81.274 67.302 68.269 77.161
> 74.145 78.295 77.27 72.616 72.712 79.06
> 70.305 77.643 75.855 72.475 75.712 77.735
> 74.288 73.986 75.955 69.229 73.062 78.814
> 72.029 79.947 78.312 71.551 74.392 78.564
> 71.499 77.615 77.042 69.227 74.31 78.837
> 76.188 74.471 83.562 70.759 75.256 76.6
> 73.236 75.606 78.743 69.966 76.001 78.464
> 69.427 77.271 76.691 69.068 75.218 80.321
> 72.473 76.978 80.643 72.057 77.151 79.068
>
> avg 72.545 76.767 78.534 70.425 74.2083 78.462
> std 1.89 1.71 2.41 1.66 2.34 1.00
> min 69.427 73.986 75.855 67.302 68.269 76.6
> max 76.188 79.947 83.562 72.616 77.151 80.321
>
>
> OK. the degression is disappeared.
>
>
>
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> Acked-by: Rik van Riel <riel@...hat.com>
> ---
> mm/vmscan.c | 15 +++++++++------
> 1 file changed, 9 insertions(+), 6 deletions(-)
>
> Index: b/mm/vmscan.c
> ===================================================================
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1418,6 +1418,8 @@ static void shrink_zone(int priority, st
> unsigned long nr_to_scan;
> unsigned long percent[2]; /* anon @ 0; file @ 1 */
> enum lru_list l;
> + unsigned long nr_reclaimed = sc->nr_reclaimed;
> + unsigned long swap_cluster_max = sc->swap_cluster_max;
>
> get_scan_ratio(zone, sc, percent);
>
> @@ -1433,7 +1435,7 @@ static void shrink_zone(int priority, st
> }
> zone->lru[l].nr_scan += scan;
> nr[l] = zone->lru[l].nr_scan;
> - if (nr[l] >= sc->swap_cluster_max)
> + if (nr[l] >= swap_cluster_max)
> zone->lru[l].nr_scan = 0;
> else
> nr[l] = 0;
> @@ -1452,12 +1454,11 @@ static void shrink_zone(int priority, st
> nr[LRU_INACTIVE_FILE]) {
> for_each_evictable_lru(l) {
> if (nr[l]) {
> - nr_to_scan = min(nr[l],
> - (unsigned long)sc->swap_cluster_max);
> + nr_to_scan = min(nr[l], swap_cluster_max);
> nr[l] -= nr_to_scan;
>
> - sc->nr_reclaimed += shrink_list(l, nr_to_scan,
> - zone, sc, priority);
> + nr_reclaimed += shrink_list(l, nr_to_scan,
> + zone, sc, priority);
> }
> }
> /*
> @@ -1468,11 +1469,13 @@ static void shrink_zone(int priority, st
> * with multiple processes reclaiming pages, the total
> * freeing target can get unreasonably large.
> */
> - if (sc->nr_reclaimed > sc->swap_cluster_max &&
> + if (nr_reclaimed > swap_cluster_max &&
> priority < DEF_PRIORITY && !current_is_kswapd())
> break;
> }
>
> + sc->nr_reclaimed = nr_reclaimed;
> +
> /*
> * Even if we did not try to evict anon pages at all, we want to
> * rebalance the anon lru active/inactive ratio.
>
>
> --
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>
--
Kinds regards,
MinChan Kim
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