[PATCH] VM: add vm.free_node_memory sysctl
From: Martin Hicks
Date: Wed Aug 03 2005 - 08:58:22 EST
On Tue, Aug 02, 2005 at 11:07:46PM +0200, Ingo Molnar wrote:
>
> * Martin Hicks <mort@xxxxxxx> wrote:
>
> > On Mon, Aug 01, 2005 at 09:54:26PM +0200, Ingo Molnar wrote:
> > >
> > > * Andrew Morton <akpm@xxxxxxxx> wrote:
> > >
> > > > > We could perhaps add a CAP_SYS_ADMIN-only sysctl for this hack,
> > > >
> > > > That would be more appropriate.
> > > >
> > > > (I'm still not sure what happened to the idea of adding a call to
> > > > "clear out this node+zone's pagecache now" rather than "set this
> > > > noed+zone's policy")
> > >
> > > lets do that as a sysctl hack. It would be useful for debugging purposes
> > > anyway. But i'm not sure whether it's the same issue - Martin?
> >
> > (Sorry..I was on vacation yesterday)
> >
> > Yes, this is the same issue with a different way of making it happen.
> > Setting a zone's policy allows reclaim to happen automatically.
> >
> > I'll send in a patch to add a sysctl to do the manual dumping of
> > pagecache really soon.
>
> cool! [ Incidentally, when i found this problem i was looking for
> existing bits in the kernel to write such a patch myself (which i wanted
> to use on non-NUMA to create more reproducable workloads for
> performance-testing) - now i'll wait for your patch. ]
Here's the promised sysctl to dump a node's pagecache. Please review!
This patch depends on the zone reclaim atomic ops cleanup:
http://marc.theaimsgroup.com/?l=linux-mm&m=112307646306476&w=2
I split up zone_reclaim():
- __zone_reclaim() does the Real Work
- zone_reclaim() checks the rate-limiting stuff.
For the sysctl we don't want to be rate limited. We always want to scan
the LRU lists looking for tossable pages.
Thanks,
mh
--
Martin Hicks || Silicon Graphics Inc. || mort@xxxxxxx
This patch adds the vm.free_node_memory sysctl. This allows a root user
to ask the kernel to drop as many pages as possible out of the specified
node's pagecache.
Takes a single integer nodeID. e.g.,
echo 14 > /proc/sys/vm/free_zone_memory
will clear pagecache on node 14.
Signed-off-by: Martin Hicks <mort@xxxxxxx>
---
commit 9b0a83e09e4fea07cf877dc7f6ff8b38c0f48d61
tree 58d5467efa7f3bf103203e25c95c6f0936ed653f
parent 414acb15f0f237cbf560bfa56c74ca9d19c5cd5a
author Martin Hicks,,,,,,,engr <mort@xxxxxxxxxxxxxxxxxxxxx> Wed, 03 Aug 2005 06:53:33 -0700
committer Martin Hicks,,,,,,,engr <mort@xxxxxxxxxxxxxxxxxxxxx> Wed, 03 Aug 2005 06:53:33 -0700
include/linux/mmzone.h | 3 ++
include/linux/sysctl.h | 1 +
kernel/sysctl.c | 10 +++++++
mm/vmscan.c | 66 +++++++++++++++++++++++++++++++++++++++---------
4 files changed, 68 insertions(+), 12 deletions(-)
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -403,6 +403,9 @@ int min_free_kbytes_sysctl_handler(struc
extern int sysctl_lowmem_reserve_ratio[MAX_NR_ZONES-1];
int lowmem_reserve_ratio_sysctl_handler(struct ctl_table *, int, struct file *,
void __user *, size_t *, loff_t *);
+extern int sysctl_free_node_memory;
+int free_node_memory_sysctl_handler(struct ctl_table *, int, struct file *,
+ void __user *, size_t *, loff_t *);
#include <linux/topology.h>
/* Returns the number of the current Node. */
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -180,6 +180,7 @@ enum
VM_VFS_CACHE_PRESSURE=26, /* dcache/icache reclaim pressure */
VM_LEGACY_VA_LAYOUT=27, /* legacy/compatibility virtual address space layout */
VM_SWAP_TOKEN_TIMEOUT=28, /* default time for token time out */
+ VM_FREE_NODE_MEMORY=29, /* free page cache from specified node */
};
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -851,6 +851,16 @@ static ctl_table vm_table[] = {
.strategy = &sysctl_jiffies,
},
#endif
+ {
+ .ctl_name = VM_FREE_NODE_MEMORY,
+ .procname = "free_node_memory",
+ .data = &sysctl_free_node_memory,
+ .maxlen = sizeof(sysctl_free_node_memory),
+ .mode = 0644,
+ .proc_handler = &free_node_memory_sysctl_handler,
+ .strategy = &sysctl_intvec,
+ .extra1 = &zero,
+ },
{ .ctl_name = 0 }
};
diff --git a/mm/vmscan.c b/mm/vmscan.c
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -33,6 +33,7 @@
#include <linux/cpuset.h>
#include <linux/notifier.h>
#include <linux/rwsem.h>
+#include <linux/sysctl.h>
#include <asm/tlbflush.h>
#include <asm/div64.h>
@@ -1329,21 +1330,17 @@ static int __init kswapd_init(void)
module_init(kswapd_init)
-
/*
- * Try to free up some pages from this zone through reclaim.
+ * Try to free up pages from the zone through reclaim.
*/
-int zone_reclaim(struct zone *zone, unsigned int gfp_mask, unsigned int order)
+int __zone_reclaim(struct zone *zone, unsigned int gfp_mask, unsigned int order)
{
struct scan_control sc;
int nr_pages = 1 << order;
- int total_reclaimed = 0;
/* The reclaim may sleep, so don't do it if sleep isn't allowed */
if (!(gfp_mask & __GFP_WAIT))
return 0;
- if (zone->all_unreclaimable)
- return 0;
sc.gfp_mask = gfp_mask;
sc.may_writepage = 0;
@@ -1359,15 +1356,22 @@ int zone_reclaim(struct zone *zone, unsi
else
sc.swap_cluster_max = SWAP_CLUSTER_MAX;
+ shrink_zone(zone, &sc);
+ return sc.nr_reclaimed;
+}
+
+/*
+ * Checks to make sure that reclaim isn't active on the zone already
+ */
+int zone_reclaim(struct zone *zone, unsigned int gfp_mask, unsigned int order)
+{
+ if (zone->all_unreclaimable)
+ return 0;
/* Don't reclaim the zone if there are other reclaimers active */
if (atomic_read(&zone->reclaim_in_progress) > 0)
- goto out;
-
- shrink_zone(zone, &sc);
- total_reclaimed = sc.nr_reclaimed;
+ return 0;
- out:
- return total_reclaimed;
+ return __zone_reclaim(zone, gfp_mask, order);
}
asmlinkage long sys_set_zone_reclaim(unsigned int node, unsigned int zone,
@@ -1393,6 +1397,44 @@ asmlinkage long sys_set_zone_reclaim(uns
z->reclaim_pages = 1;
else
z->reclaim_pages = 0;
+ }
+
+ return 0;
+}
+
+int sysctl_free_node_memory;
+static DECLARE_MUTEX(free_node_memory_lock);
+
+int free_node_memory_sysctl_handler(ctl_table *table, int write,
+ struct file *file, void __user *buffer,
+ size_t *length, loff_t *ppos)
+{
+ struct zone *z;
+ int node;
+ int gfp_mask = __GFP_WAIT;
+ int i;
+
+ if (!write)
+ return 0;
+
+ down_interruptible(&free_node_memory_lock);
+ proc_dointvec(table, write, file, buffer, length, ppos);
+
+ node = sysctl_free_node_memory;
+ up(&free_node_memory_lock);
+
+ if (node >= MAX_NUMNODES || !node_online(node))
+ return -EINVAL;
+
+ for (i = 0; i < MAX_NR_ZONES; i++) {
+ z = &NODE_DATA(node)->node_zones[i];
+
+ if (!z->present_pages)
+ continue;
+
+ /* Reclaim pages from the zone */
+ while (__zone_reclaim(z, gfp_mask, SWAP_CLUSTER_MAX) != 0)
+ ;
}
return 0;
-
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