On 03.07.2015 15:20, Pintu Kumar wrote: > 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 The API should be as restrictive as possible to allow for extensibility. You describe "1" as the only used value. So, please add here: "If any other value than 1 is written to shrink_memory an error EINVAL occurs." > + > +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, Supply the value limits. int min_shrink_memory = 1; int max_shrink_memory = 1; .extra1 = &min_shrink_memory, .extra2 = &max_shrink_memory, > + }, > +#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) > +{ Check if *buffer contains "1". If the value is not "1" return -EINVAL. The check can be done using function proc_dointvec_minmax(). Best regards Heinrich Schuchardt > + 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, > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>