mm: honor min_free_kbytes set by user
min_free_kbytes is updated during memory hotplug (by init_per_zone_wmark_min) currently which is right thing to do in most cases but this could be unexpected if admin increased the value to prevent from allocation failures and the new min_free_kbytes would be decreased as a result of memory hotadd. This patch saves the user defined value and allows updating min_free_kbytes only if it is higher than the saved one. A warning is printed when the new value is ignored. Signed-off-by: Michal Hocko <mhocko@suse.cz> Cc: Mel Gorman <mgorman@suse.de> Acked-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com> Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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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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@ -5589,14 +5590,21 @@ 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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new_min_free_kbytes = int_sqrt(lowmem_kbytes * 16);
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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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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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@ -5614,8 +5622,10 @@ 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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