mm: Add min_free_order_shift tunable.

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>

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index f175d98bd3557c912e15f65fcd98be713f400f29..ea468b1232ac39385d46e59e7200d6a32409a4e0 100644 (file)
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -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;
@@ -1188,6 +1189,13 @@ static struct ctl_table vm_table[] = {
                .proc_handler   = min_free_kbytes_sysctl_handler,
                .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,

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 4e8985acdab8b5c234a6486b3c84caf5fb89dca0..fef8dc3b11a4e7a5b6b4af5a565bf04fda1c1237 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -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;
@@ -1487,7 +1488,7 @@ 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;