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Date: Fri, 03 Jul 2015 19:21:19 +0200
From: Heinrich Schuchardt <xypron.glpk@....de>
To: Pintu Kumar <pintu.k@...sung.com>, corbet@....net,
akpm@...ux-foundation.org, vbabka@...e.cz, gorcunov@...nvz.org,
mhocko@...e.cz, emunson@...mai.com,
kirill.shutemov@...ux.intel.com, standby24x7@...il.com,
hannes@...xchg.org, vdavydov@...allels.com, hughd@...gle.com,
minchan@...nel.org, tj@...nel.org, rientjes@...gle.com,
dzickus@...hat.com, prarit@...hat.com, ebiederm@...ssion.com,
rostedt@...dmis.org, uobergfe@...hat.com,
paulmck@...ux.vnet.ibm.com, iamjoonsoo.kim@....com,
ddstreet@...e.org, sasha.levin@...cle.com, koct9i@...il.com,
mgorman@...e.de, cj@...ux.com, opensource.ganesh@...il.com,
vinmenon@...eaurora.org, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
linux-pm@...r.kernel.org
CC: cpgs@...sung.com, pintu_agarwal@...oo.com, vishnu.ps@...sung.com,
rohit.kr@...sung.com, iqbal.ams@...sung.com
Subject: Re: [PATCH 1/1] kernel/sysctl.c: Add /proc/sys/vm/shrink_memory feature
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@...sung.com>
> ---
> 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,
>
--
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