Messages in this thread | | | Date | Thu, 7 Jan 2010 14:00:16 -0800 (PST) | From | David Rientjes <> | Subject | Re: [PATCH 5/7] Add /proc trigger for memory compaction |
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On Wed, 6 Jan 2010, Mel Gorman wrote:
> This patch adds a proc file /proc/sys/vm/compact_node. When a NID is written > to the file, each zone in that node is compacted. This should be done with > debugfs but this was what was available to rebase quickly and I suspect > debugfs either did not exist or was in development during the first > implementation. > > If this interface is to exist in the long term, it needs to be thought > about carefully. For the moment, it's handy to have to test compaction > under a controlled setting. >
With Lee's work on mempolicy-constrained hugepage allocations, there is a use-case for this explicit trigger to be exported via sysfs in the longterm: we should be able to determine how successful the allocation of hugepages will be on a particular node without actually allocating them depending on the degree of external fragmentation to form our mempolicy. Since node-targeted hugepage allocation and freeing now exists in the kernel and compaction is used primary for the former, I don't see why it shouldn't be exposed.
I like the (slightly racy) interface that avoids having a trigger for each node under /sys/devices/system/node as well.
> Signed-off-by: Mel Gorman <mel@csn.ul.ie> > --- > include/linux/compaction.h | 5 ++++ > kernel/sysctl.c | 11 +++++++++ > mm/compaction.c | 52 ++++++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 68 insertions(+), 0 deletions(-) > > diff --git a/include/linux/compaction.h b/include/linux/compaction.h > index 6201371..5965ef2 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_MIGRATION > +extern int sysctl_compaction_handler(struct ctl_table *table, int write, > + void __user *buffer, size_t *length, loff_t *ppos); > +#endif /* CONFIG_MIGRATION */ > + > #endif /* _LINUX_COMPACTION_H */ > diff --git a/kernel/sysctl.c b/kernel/sysctl.c > index 8a68b24..6202e95 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_node; > 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_MIGRATION > + { > + .procname = "compact_node", > + .data = &sysctl_compact_node, > + .maxlen = sizeof(int), > + .mode = 0644,
This should only need 0200?
> + .proc_handler = sysctl_compaction_handler, > + }, > +#endif /* CONFIG_MIGRATION */ > { > .procname = "min_free_kbytes", > .data = &min_free_kbytes, > diff --git a/mm/compaction.c b/mm/compaction.c > index d36760a..a8bcae2 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" > > /* > @@ -338,3 +339,54 @@ static int compact_zone(struct zone *zone, struct compact_control *cc) > return ret; > } > > +/* Compact all zones within a node */ > +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(); > + > + printk(KERN_INFO "Compacting memory in node %d\n", nid); > + 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)); > + } > + printk(KERN_INFO "Compaction of node %d complete\n", nid);
If it's exposed through sysfs, the printk's should probably be demoted to pr_debug().
> + > + return 0; > +} > + > +/* This is global and fierce ugly but it's straight-forward */ > +int sysctl_compact_node; > + > +/* This is the entry point for compacting nodes via /proc/sys/vm */ > +int sysctl_compaction_handler(struct ctl_table *table, int write, > + void __user *buffer, size_t *length, loff_t *ppos) > +{ > + proc_dointvec(table, write, buffer, length, ppos); > + if (write) > + return compact_node(sysctl_compact_node); > + > + return 0; > +}
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