Re: [PATCH 09/12] Add /proc trigger for memory compaction

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

On Thu, 18 Feb 2010 18:02:39 +0000
Mel Gorman <mel@csn.ul.ie> wrote:

> This patch adds a proc file /proc/sys/vm/compact_memory. When an arbitrary
> value is written to the file, all zones are compacted. The expected user
> of such a trigger is a job scheduler that prepares the system before the
> target application runs.
> 
> Signed-off-by: Mel Gorman <mel@csn.ul.ie>
> Acked-by: Rik van Riel <riel@redhat.com>

Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

Nitpick:
Hmm.. Is this necessary if we have per-node trigger in sysfs ?

Thanks,
-Kame


> ---
>  Documentation/sysctl/vm.txt |   11 ++++++++
>  include/linux/compaction.h  |    5 +++
>  kernel/sysctl.c             |   11 ++++++++
>  mm/compaction.c             |   60 +++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 87 insertions(+), 0 deletions(-)
> 
> diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt
> index fc5790d..92b5b00 100644
> --- a/Documentation/sysctl/vm.txt
> +++ b/Documentation/sysctl/vm.txt
> @@ -19,6 +19,7 @@ files can be found in mm/swap.c.
>  Currently, these files are in /proc/sys/vm:
>  
>  - block_dump
> +- compact_memory
>  - dirty_background_bytes
>  - dirty_background_ratio
>  - dirty_bytes
> @@ -64,6 +65,16 @@ information on block I/O debugging is in Documentation/laptops/laptop-mode.txt.
>  
>  ==============================================================
>  
> +compact_memory
> +
> +Available only when CONFIG_COMPACTION is set. When an arbitrary value
> +is written to the file, all zones are compacted such that free memory
> +is available in contiguous blocks where possible. This can be important
> +for example in the allocation of huge pages although processes will also
> +directly compact memory as required.
> +
> +==============================================================
> +
>  dirty_background_bytes
>  
>  Contains the amount of dirty memory at which the pdflush background writeback
> diff --git a/include/linux/compaction.h b/include/linux/compaction.h
> index 6201371..facaa3d 100644
> --- a/include/linux/compaction.h
> +++ b/include/linux/compaction.h
> @@ -5,4 +5,9 @@
>  #define COMPACT_INCOMPLETE	0
>  #define COMPACT_COMPLETE	1
>  
> +#ifdef CONFIG_COMPACTION
> +extern int sysctl_compaction_handler(struct ctl_table *table, int write,
> +			void __user *buffer, size_t *length, loff_t *ppos);
> +#endif /* CONFIG_COMPACTION */
> +
>  #endif /* _LINUX_COMPACTION_H */
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 8a68b24..a02c816 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -50,6 +50,7 @@
>  #include <linux/ftrace.h>
>  #include <linux/slow-work.h>
>  #include <linux/perf_event.h>
> +#include <linux/compaction.h>
>  
>  #include <asm/uaccess.h>
>  #include <asm/processor.h>
> @@ -80,6 +81,7 @@ extern int pid_max;
>  extern int min_free_kbytes;
>  extern int pid_max_min, pid_max_max;
>  extern int sysctl_drop_caches;
> +extern int sysctl_compact_memory;
>  extern int percpu_pagelist_fraction;
>  extern int compat_log;
>  extern int latencytop_enabled;
> @@ -1109,6 +1111,15 @@ static struct ctl_table vm_table[] = {
>  		.mode		= 0644,
>  		.proc_handler	= drop_caches_sysctl_handler,
>  	},
> +#ifdef CONFIG_COMPACTION
> +	{
> +		.procname	= "compact_memory",
> +		.data		= &sysctl_compact_memory,
> +		.maxlen		= sizeof(int),
> +		.mode		= 0200,
> +		.proc_handler	= sysctl_compaction_handler,
> +	},
> +#endif /* CONFIG_COMPACTION */
>  	{
>  		.procname	= "min_free_kbytes",
>  		.data		= &min_free_kbytes,
> diff --git a/mm/compaction.c b/mm/compaction.c
> index 14ba0ac..22f223f 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -11,6 +11,7 @@
>  #include <linux/migrate.h>
>  #include <linux/compaction.h>
>  #include <linux/mm_inline.h>
> +#include <linux/sysctl.h>
>  #include "internal.h"
>  
>  /*
> @@ -345,3 +346,62 @@ static int compact_zone(struct zone *zone, struct compact_control *cc)
>  	return ret;
>  }
>  
> +/* Compact all zones within a node */
> +static int compact_node(int nid)
> +{
> +	int zoneid;
> +	pg_data_t *pgdat;
> +	struct zone *zone;
> +
> +	if (nid < 0 || nid > nr_node_ids || !node_online(nid))
> +		return -EINVAL;
> +	pgdat = NODE_DATA(nid);
> +
> +	/* Flush pending updates to the LRU lists */
> +	lru_add_drain_all();
> +
> +	for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
> +		struct compact_control cc;
> +
> +		zone = &pgdat->node_zones[zoneid];
> +		if (!populated_zone(zone))
> +			continue;
> +
> +		cc.nr_freepages = 0;
> +		cc.nr_migratepages = 0;
> +		cc.zone = zone;
> +		INIT_LIST_HEAD(&cc.freepages);
> +		INIT_LIST_HEAD(&cc.migratepages);
> +
> +		compact_zone(zone, &cc);
> +
> +		VM_BUG_ON(!list_empty(&cc.freepages));
> +		VM_BUG_ON(!list_empty(&cc.migratepages));
> +	}
> +
> +	return 0;
> +}
> +
> +/* Compact all nodes in the system */
> +static int compact_nodes(void)
> +{
> +	int nid;
> +
> +	for_each_online_node(nid)
> +		compact_node(nid);
> +
> +	return COMPACT_COMPLETE;
> +}
> +
> +/* The written value is actually unused, all memory is compacted */
> +int sysctl_compact_memory;
> +
> +/* This is the entry point for compacting all nodes via /proc/sys/vm */
> +int sysctl_compaction_handler(struct ctl_table *table, int write,
> +			void __user *buffer, size_t *length, loff_t *ppos)
> +{
> +	if (write)
> +		return compact_nodes();
> +
> +	return 0;
> +}
> -- 
> 1.6.5
> 
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