mm: Add min_free_order_shift tunable.
Arve Hjønnevåg [Tue, 17 Feb 2009 22:51:02 +0000 (14:51 -0800)]
By default the kernel tries to keep half as much memory free at each
order as it does for one order below. This can be too agressive when
running without swap.

Change-Id: I5efc1a0b50f41ff3ac71e92d2efd175dedd54ead
Signed-off-by: Arve Hjønnevåg <arve@android.com>

kernel/sysctl.c
mm/page_alloc.c

index 11d65b5..fd15163 100644 (file)
@@ -96,6 +96,7 @@ extern char core_pattern[];
 extern unsigned int core_pipe_limit;
 extern int pid_max;
 extern int min_free_kbytes;
+extern int min_free_order_shift;
 extern int pid_max_min, pid_max_max;
 extern int sysctl_drop_caches;
 extern int percpu_pagelist_fraction;
@@ -1189,6 +1190,13 @@ static struct ctl_table vm_table[] = {
                .extra1         = &zero,
        },
        {
+               .procname       = "min_free_order_shift",
+               .data           = &min_free_order_shift,
+               .maxlen         = sizeof(min_free_order_shift),
+               .mode           = 0644,
+               .proc_handler   = &proc_dointvec
+       },
+       {
                .procname       = "percpu_pagelist_fraction",
                .data           = &percpu_pagelist_fraction,
                .maxlen         = sizeof(percpu_pagelist_fraction),
index 6e8ecb6..4125353 100644 (file)
@@ -176,6 +176,7 @@ static char * const zone_names[MAX_NR_ZONES] = {
 };
 
 int min_free_kbytes = 1024;
+int min_free_order_shift = 1;
 
 static unsigned long __meminitdata nr_kernel_pages;
 static unsigned long __meminitdata nr_all_pages;
@@ -1469,7 +1470,7 @@ static bool __zone_watermark_ok(struct zone *z, int order, unsigned long mark,
                free_pages -= z->free_area[o].nr_free << o;
 
                /* Require fewer higher order pages to be free */
-               min >>= 1;
+               min >>= min_free_order_shift;
 
                if (free_pages <= min)
                        return false;