[PATCH 1/1] kernel/sysctl.c: Add /proc/sys/vm/shrink_memory feature
From: Pintu Kumar
Date: Fri Jul 03 2015 - 09:33:24 EST
This patch provides 2 things:
1. Add new control called shrink_memory in /proc/sys/vm/.
This control can be used to aggressively reclaim memory system-wide
in one shot from the user space. A value of 1 will instruct the
kernel to reclaim as much as totalram_pages in the system.
Example: echo 1 > /proc/sys/vm/shrink_memory
2. Enable shrink_all_memory API in kernel with new CONFIG_SHRINK_MEMORY.
Currently, shrink_all_memory function is used only during hibernation.
With the new config we can make use of this API for non-hibernation case
also without disturbing the hibernation case.
The detailed paper was presented in Embedded Linux Conference, Mar-2015
http://events.linuxfoundation.org/sites/events/files/slides/
%5BELC-2015%5D-System-wide-Memory-Defragmenter.pdf
Scenarios were this can be used and helpful are:
1) Can be invoked just after system boot-up is finished.
2) Can be invoked just before entering entire system suspend.
3) Can be invoked from kernel when order-4 pages starts failing.
4) Can be helpful to completely avoid or delay the kerenl OOM condition.
5) Can be developed as a system-tool to quickly defragment entire system
from user space, without the need to kill any application.
Signed-off-by: Pintu Kumar <pintu.k@xxxxxxxxxxx>
---
Documentation/sysctl/vm.txt | 16 ++++++++++++++++
include/linux/swap.h | 7 +++++++
kernel/sysctl.c | 9 +++++++++
mm/Kconfig | 8 ++++++++
mm/vmscan.c | 23 +++++++++++++++++++++--
5 files changed, 61 insertions(+), 2 deletions(-)
diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt
index 9832ec5..a959ad1 100644
--- a/Documentation/sysctl/vm.txt
+++ b/Documentation/sysctl/vm.txt
@@ -54,6 +54,7 @@ Currently, these files are in /proc/sys/vm:
- page-cluster
- panic_on_oom
- percpu_pagelist_fraction
+- shrink_memory
- stat_interval
- swappiness
- user_reserve_kbytes
@@ -718,6 +719,21 @@ sysctl, it will revert to this default behavior.
==============================================================
+shrink_memory
+
+This control is available only when CONFIG_SHRINK_MEMORY is set. This control
+can be used to aggressively reclaim memory system-wide in one shot. A value of
+1 will instruct the kernel to reclaim as much as totalram_pages in the system.
+For example, to reclaim all memory system-wide we can do:
+# echo 1 > /proc/sys/vm/shrink_memory
+
+For more information about this control, please visit the following
+presentation in embedded linux conference, 2015.
+http://events.linuxfoundation.org/sites/events/files/slides/
+%5BELC-2015%5D-System-wide-Memory-Defragmenter.pdf
+
+==============================================================
+
stat_interval
The time interval between which vm statistics are updated. The default
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 9a7adfb..6505b0b 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -333,6 +333,13 @@ extern int vm_swappiness;
extern int remove_mapping(struct address_space *mapping, struct page *page);
extern unsigned long vm_total_pages;
+#ifdef CONFIG_SHRINK_MEMORY
+extern int sysctl_shrink_memory;
+extern int sysctl_shrinkmem_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *length, loff_t *ppos);
+#endif
+
+
#ifdef CONFIG_NUMA
extern int zone_reclaim_mode;
extern int sysctl_min_unmapped_ratio;
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index c566b56..2895099 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1351,6 +1351,15 @@ static struct ctl_table vm_table[] = {
},
#endif /* CONFIG_COMPACTION */
+#ifdef CONFIG_SHRINK_MEMORY
+ {
+ .procname = "shrink_memory",
+ .data = &sysctl_shrink_memory,
+ .maxlen = sizeof(int),
+ .mode = 0200,
+ .proc_handler = sysctl_shrinkmem_handler,
+ },
+#endif
{
.procname = "min_free_kbytes",
.data = &min_free_kbytes,
diff --git a/mm/Kconfig b/mm/Kconfig
index b3a60ee..8e04bd9 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -657,3 +657,11 @@ config DEFERRED_STRUCT_PAGE_INIT
when kswapd starts. This has a potential performance impact on
processes running early in the lifetime of the systemm until kswapd
finishes the initialisation.
+
+config SHRINK_MEMORY
+ bool "Allow for system-wide shrinking of memory"
+ default n
+ depends on MMU
+ help
+ It enables support for system-wide memory reclaim in one shot using
+ echo 1 > /proc/sys/vm/shrink_memory.
diff --git a/mm/vmscan.c b/mm/vmscan.c
index c8d8282..837b88d 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3557,7 +3557,7 @@ void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
wake_up_interruptible(&pgdat->kswapd_wait);
}
-#ifdef CONFIG_HIBERNATION
+#if defined CONFIG_HIBERNATION || CONFIG_SHRINK_MEMORY
/*
* Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
* freed pages.
@@ -3571,12 +3571,17 @@ unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
struct reclaim_state reclaim_state;
struct scan_control sc = {
.nr_to_reclaim = nr_to_reclaim,
+#ifdef CONFIG_SHRINK_MEMORY
+ .gfp_mask = (GFP_HIGHUSER_MOVABLE | GFP_RECLAIM_MASK),
+ .hibernation_mode = 0,
+#else
.gfp_mask = GFP_HIGHUSER_MOVABLE,
+ .hibernation_mode = 1,
+#endif
.priority = DEF_PRIORITY,
.may_writepage = 1,
.may_unmap = 1,
.may_swap = 1,
- .hibernation_mode = 1,
};
struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
struct task_struct *p = current;
@@ -3597,6 +3602,20 @@ unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
}
#endif /* CONFIG_HIBERNATION */
+#ifdef CONFIG_SHRINK_MEMORY
+int sysctl_shrink_memory;
+/* This is the entry point for system-wide shrink memory
++via /proc/sys/vm/shrink_memory */
+int sysctl_shrinkmem_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *length, loff_t *ppos)
+{
+ if (write)
+ shrink_all_memory(totalram_pages);
+
+ return 0;
+}
+#endif
+
/* It's optimal to keep kswapds on the same CPUs as their memory, but
not required for correctness. So if the last cpu in a node goes
away, we get changed to run anywhere: as the first one comes back,
--
1.7.9.5
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