Re: [RFC] mm: Honor min_free_kbytes set by user
From: Zhang Yanfei
Date: Thu Jul 04 2013 - 12:35:53 EST
On 07/05/2013 12:20 AM, Michal Hocko wrote:
[snip]
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---
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From 5f089c0b2a57ff6c08710ac9698d65aede06079f Mon Sep 17 00:00:00 2001
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From: Michal Hocko <mhocko@xxxxxxx>
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Date: Thu, 4 Jul 2013 17:15:54 +0200
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Subject: [PATCH] mm: Honor min_free_kbytes set by user
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min_free_kbytes is updated during memory hotplug (by init_per_zone_wmark_min)
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currently which is right thing to do in most cases but this could be
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unexpected if admin increased the value to prevent from allocation
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failures and the new min_free_kbytes would be decreased as a result of
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memory hotadd.
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This patch saves the user defined value and allows updating
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min_free_kbytes only if it is higher than the saved one.
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A warning is printed when the new value is ignored.
Looks reasonable.
Acked-by: Zhang Yanfei <zhangyanfei@xxxxxxxxxxxxxx>
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Signed-off-by: Michal Hocko <mhocko@xxxxxxx>
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---
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mm/page_alloc.c | 24 +++++++++++++++++-------
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1 file changed, 17 insertions(+), 7 deletions(-)
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diff --git a/mm/page_alloc.c b/mm/page_alloc.c
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index 22c528e..9c011fc 100644
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--- a/mm/page_alloc.c
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+++ b/mm/page_alloc.c
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@@ -204,6 +204,7 @@ static char * const zone_names[MAX_NR_ZONES] = {
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};
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int min_free_kbytes = 1024;
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+int user_min_free_kbytes;
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static unsigned long __meminitdata nr_kernel_pages;
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static unsigned long __meminitdata nr_all_pages;
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@@ -5592,14 +5593,21 @@ static void __meminit setup_per_zone_inactive_ratio(void)
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int __meminit init_per_zone_wmark_min(void)
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{
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unsigned long lowmem_kbytes;
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+ int new_min_free_kbytes;
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lowmem_kbytes = nr_free_buffer_pages() * (PAGE_SIZE >> 10);
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-
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- min_free_kbytes = int_sqrt(lowmem_kbytes * 16);
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- if (min_free_kbytes < 128)
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- min_free_kbytes = 128;
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- if (min_free_kbytes > 65536)
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- min_free_kbytes = 65536;
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+ new_min_free_kbytes = int_sqrt(lowmem_kbytes * 16);
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+
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+ if (new_min_free_kbytes > user_min_free_kbytes) {
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+ min_free_kbytes = new_min_free_kbytes;
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+ if (min_free_kbytes < 128)
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+ min_free_kbytes = 128;
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+ if (min_free_kbytes > 65536)
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+ min_free_kbytes = 65536;
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+ } else {
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+ pr_warn("min_free_kbytes is not updated to %d because user defined value %d is preferred\n",
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+ new_min_free_kbytes, user_min_free_kbytes);
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+ }
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setup_per_zone_wmarks();
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refresh_zone_stat_thresholds();
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setup_per_zone_lowmem_reserve();
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@@ -5617,8 +5625,10 @@ int min_free_kbytes_sysctl_handler(ctl_table *table, int write,
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void __user *buffer, size_t *length, loff_t *ppos)
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{
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proc_dointvec(table, write, buffer, length, ppos);
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- if (write)
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+ if (write) {
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+ user_min_free_kbytes = min_free_kbytes;
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setup_per_zone_wmarks();
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+ }
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return 0;
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}
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--
Thanks.
Zhang Yanfei
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