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Message-ID: <44c63dc40802200056va847417v1cfc847341bb8cc0@mail.gmail.com>
Date: Wed, 20 Feb 2008 17:56:02 +0900
From: "minchan Kim" <barrioskmc@...il.com>
To: "KOSAKI Motohiro" <kosaki.motohiro@...fujitsu.com>
Cc: "KAMEZAWA Hiroyuki" <kamezawa.hiroyu@...fujitsu.com>,
"Balbir Singh" <balbir@...ux.vnet.ibm.com>,
"Rik van Riel" <riel@...hat.com>,
"Lee Schermerhorn" <Lee.Schermerhorn@...com>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH] the proposal of improve page reclaim by throttle
Hi, KOSAKI.
I am a many interested in your patch. so I want to test it with exact
same method as you did.
I will test it in embedded environment(ARM 920T, 32M ram) and my
desktop machine.(Core2Duo 2.2G, 2G ram)
I guess this patch won't be efficient in embedded environment.
Since many embedded board just have one processor and don't have any
swap device.
What I want to know is that this patch have a regression in UP and NO
swap device like embedded.
I think I can't show some field only top or freemem.
Becuase top or freemem won't be able to work well if system have a
great overhead with page reclaiming and swapping.
So, How do I evaluate following field as you did ?
* elapse (what do you mean it ??)
* major fault
* max parallel reclaim tasks:
* max consumption time of
try_to_free_pages():
If you have a patch for testing, Let me receive it.
On Feb 19, 2008 2:44 PM, KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> wrote:
> background
> ========================================
> current VM implementation doesn't has limit of # of parallel reclaim.
> when heavy workload, it bring to 2 bad things
> - heavy lock contention
> - unnecessary swap out
>
> abount 2 month ago, KAMEZA Hiroyuki proposed the patch of page
> reclaim throttle and explain it improve reclaim time.
> http://marc.info/?l=linux-mm&m=119667465917215&w=2
>
> but unfortunately it works only memcgroup reclaim.
> Today, I implement it again for support global reclaim and mesure it.
>
>
> test machine, method and result
> ==================================================
> <test machine>
> CPU: IA64 x8
> MEM: 8GB
> SWAP: 2GB
>
> <test method>
> got hackbench from
> http://people.redhat.com/mingo/cfs-scheduler/tools/hackbench.c
>
> $ /usr/bin/time hackbench 120 process 1000
>
> this parameter mean consume all physical memory and
> 1GB swap space on my test environment.
>
> <test result (average of 3 times measurement)>
>
> before:
> hackbench result: 282.30
> /usr/bin/time result
> user: 14.16
> sys: 1248.47
> elapse: 432.93
> major fault: 29026
> max parallel reclaim tasks: 1298
> max consumption time of
> try_to_free_pages(): 70394
>
> after:
> hackbench result: 30.36
> /usr/bin/time result
> user: 14.26
> sys: 294.44
> elapse: 118.01
> major fault: 3064
> max parallel reclaim tasks: 4
> max consumption time of
> try_to_free_pages(): 12234
>
>
> conclusion
> =========================================
> this patch improve 3 things.
> 1. reduce unnecessary swap
> (see above major fault. about 90% reduced)
> 2. improve throughput performance
> (see above hackbench result. about 90% reduced)
> 3. improve interactive performance.
> (see above max consumption of try_to_free_pages.
> about 80% reduced)
> 4. reduce lock contention.
> (see above sys time. about 80% reduced)
>
>
> Now, we got about 1000% performance improvement of hackbench :)
>
>
>
> foture works
> ==========================================================
> - more discussion with memory controller guys.
>
>
>
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> CC: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> CC: Balbir Singh <balbir@...ux.vnet.ibm.com>
> CC: Rik van Riel <riel@...hat.com>
> CC: Lee Schermerhorn <Lee.Schermerhorn@...com>
>
> ---
> include/linux/nodemask.h | 1
> mm/vmscan.c | 49 +++++++++++++++++++++++++++++++++++++++++++++--
> 2 files changed, 48 insertions(+), 2 deletions(-)
>
> Index: b/include/linux/nodemask.h
> ===================================================================
> --- a/include/linux/nodemask.h 2008-02-19 13:58:05.000000000 +0900
> +++ b/include/linux/nodemask.h 2008-02-19 13:58:23.000000000 +0900
> @@ -431,6 +431,7 @@ static inline int num_node_state(enum no
>
> #define num_online_nodes() num_node_state(N_ONLINE)
> #define num_possible_nodes() num_node_state(N_POSSIBLE)
> +#define num_highmem_nodes() num_node_state(N_HIGH_MEMORY)
> #define node_online(node) node_state((node), N_ONLINE)
> #define node_possible(node) node_state((node), N_POSSIBLE)
>
> Index: b/mm/vmscan.c
> ===================================================================
> --- a/mm/vmscan.c 2008-02-19 13:58:05.000000000 +0900
> +++ b/mm/vmscan.c 2008-02-19 14:04:06.000000000 +0900
> @@ -127,6 +127,11 @@ long vm_total_pages; /* The total number
> static LIST_HEAD(shrinker_list);
> static DECLARE_RWSEM(shrinker_rwsem);
>
> +static atomic_t nr_reclaimers = ATOMIC_INIT(0);
> +static DECLARE_WAIT_QUEUE_HEAD(reclaim_throttle_waitq);
> +#define RECLAIM_LIMIT (2 * num_highmem_nodes())
> +
> +
> #ifdef CONFIG_CGROUP_MEM_CONT
> #define scan_global_lru(sc) (!(sc)->mem_cgroup)
> #else
> @@ -1421,6 +1426,46 @@ out:
> return ret;
> }
>
> +static unsigned long try_to_free_pages_throttled(struct zone **zones,
> + int order,
> + gfp_t gfp_mask,
> + struct scan_control *sc)
> +{
> + unsigned long nr_reclaimed = 0;
> + unsigned long start_time;
> + int i;
> +
> + start_time = jiffies;
> +
> + wait_event(reclaim_throttle_waitq,
> + atomic_add_unless(&nr_reclaimers, 1, RECLAIM_LIMIT));
> +
> + /* more reclaim until needed? */
> + if (unlikely(time_after(jiffies, start_time + HZ))) {
> + for (i = 0; zones[i] != NULL; i++) {
> + struct zone *zone = zones[i];
> + int classzone_idx = zone_idx(zones[0]);
> +
> + if (!populated_zone(zone))
> + continue;
> +
> + if (zone_watermark_ok(zone, order, 4*zone->pages_high,
> + classzone_idx, 0)) {
> + nr_reclaimed = 1;
> + goto out;
> + }
> + }
> + }
> +
> + nr_reclaimed = do_try_to_free_pages(zones, gfp_mask, sc);
> +
> +out:
> + atomic_dec(&nr_reclaimers);
> + wake_up_all(&reclaim_throttle_waitq);
> +
> + return nr_reclaimed;
> +}
> +
> unsigned long try_to_free_pages(struct zone **zones, int order, gfp_t gfp_mask)
> {
> struct scan_control sc = {
> @@ -1434,7 +1479,7 @@ unsigned long try_to_free_pages(struct z
> .isolate_pages = isolate_pages_global,
> };
>
> - return do_try_to_free_pages(zones, gfp_mask, &sc);
> + return try_to_free_pages_throttled(zones, order, gfp_mask, &sc);
> }
>
> #ifdef CONFIG_CGROUP_MEM_CONT
> @@ -1456,7 +1501,7 @@ unsigned long try_to_free_mem_cgroup_pag
> int target_zone = gfp_zone(GFP_HIGHUSER_MOVABLE);
>
> zones = NODE_DATA(numa_node_id())->node_zonelists[target_zone].zones;
> - if (do_try_to_free_pages(zones, sc.gfp_mask, &sc))
> + if (try_to_free_pages_throttled(zones, 0, sc.gfp_mask, &sc))
> return 1;
> return 0;
> }
>
>
> --
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>
--
Thanks,
barrios
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