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 -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
