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authorDavid Rientjes <rientjes@google.com>2009-01-06 14:39:31 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2009-01-06 15:59:03 -0800
commit2da02997e08d3efe8174c7a47696e6f7cbe69ba9 (patch)
tree2e52d9346c52dda83dc8cc9626cbe302e026ad9a /kernel/sysctl.c
parent364aeb2849789b51bf4b9af2ddd02fee7285c54e (diff)
mm: add dirty_background_bytes and dirty_bytes sysctls
This change introduces two new sysctls to /proc/sys/vm: dirty_background_bytes and dirty_bytes. dirty_background_bytes is the counterpart to dirty_background_ratio and dirty_bytes is the counterpart to dirty_ratio. With growing memory capacities of individual machines, it's no longer sufficient to specify dirty thresholds as a percentage of the amount of dirtyable memory over the entire system. dirty_background_bytes and dirty_bytes specify quantities of memory, in bytes, that represent the dirty limits for the entire system. If either of these values is set, its value represents the amount of dirty memory that is needed to commence either background or direct writeback. When a `bytes' or `ratio' file is written, its counterpart becomes a function of the written value. For example, if dirty_bytes is written to be 8096, 8K of memory is required to commence direct writeback. dirty_ratio is then functionally equivalent to 8K / the amount of dirtyable memory: dirtyable_memory = free pages + mapped pages + file cache dirty_background_bytes = dirty_background_ratio * dirtyable_memory -or- dirty_background_ratio = dirty_background_bytes / dirtyable_memory AND dirty_bytes = dirty_ratio * dirtyable_memory -or- dirty_ratio = dirty_bytes / dirtyable_memory Only one of dirty_background_bytes and dirty_background_ratio may be specified at a time, and only one of dirty_bytes and dirty_ratio may be specified. When one sysctl is written, the other appears as 0 when read. The `bytes' files operate on a page size granularity since dirty limits are compared with ZVC values, which are in page units. Prior to this change, the minimum dirty_ratio was 5 as implemented by get_dirty_limits() although /proc/sys/vm/dirty_ratio would show any user written value between 0 and 100. This restriction is maintained, but dirty_bytes has a lower limit of only one page. Also prior to this change, the dirty_background_ratio could not equal or exceed dirty_ratio. This restriction is maintained in addition to restricting dirty_background_bytes. If either background threshold equals or exceeds that of the dirty threshold, it is implicitly set to half the dirty threshold. Acked-by: Peter Zijlstra <peterz@infradead.org> Cc: Dave Chinner <david@fromorbit.com> Cc: Christoph Lameter <cl@linux-foundation.org> Signed-off-by: David Rientjes <rientjes@google.com> Cc: Andrea Righi <righi.andrea@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/sysctl.c')
-rw-r--r--kernel/sysctl.c27
1 files changed, 22 insertions, 5 deletions
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index ff6d45c7626f..92f6e5bc3c24 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -87,10 +87,6 @@ extern int rcutorture_runnable;
#endif /* #ifdef CONFIG_RCU_TORTURE_TEST */
/* Constants used for minimum and maximum */
-#if defined(CONFIG_HIGHMEM) || defined(CONFIG_DETECT_SOFTLOCKUP)
-static int one = 1;
-#endif
-
#ifdef CONFIG_DETECT_SOFTLOCKUP
static int sixty = 60;
static int neg_one = -1;
@@ -101,6 +97,7 @@ static int two = 2;
#endif
static int zero;
+static int one = 1;
static int one_hundred = 100;
/* this is needed for the proc_dointvec_minmax for [fs_]overflow UID and GID */
@@ -952,12 +949,22 @@ static struct ctl_table vm_table[] = {
.data = &dirty_background_ratio,
.maxlen = sizeof(dirty_background_ratio),
.mode = 0644,
- .proc_handler = &proc_dointvec_minmax,
+ .proc_handler = &dirty_background_ratio_handler,
.strategy = &sysctl_intvec,
.extra1 = &zero,
.extra2 = &one_hundred,
},
{
+ .ctl_name = CTL_UNNUMBERED,
+ .procname = "dirty_background_bytes",
+ .data = &dirty_background_bytes,
+ .maxlen = sizeof(dirty_background_bytes),
+ .mode = 0644,
+ .proc_handler = &dirty_background_bytes_handler,
+ .strategy = &sysctl_intvec,
+ .extra1 = &one,
+ },
+ {
.ctl_name = VM_DIRTY_RATIO,
.procname = "dirty_ratio",
.data = &vm_dirty_ratio,
@@ -969,6 +976,16 @@ static struct ctl_table vm_table[] = {
.extra2 = &one_hundred,
},
{
+ .ctl_name = CTL_UNNUMBERED,
+ .procname = "dirty_bytes",
+ .data = &vm_dirty_bytes,
+ .maxlen = sizeof(vm_dirty_bytes),
+ .mode = 0644,
+ .proc_handler = &dirty_bytes_handler,
+ .strategy = &sysctl_intvec,
+ .extra1 = &one,
+ },
+ {
.procname = "dirty_writeback_centisecs",
.data = &dirty_writeback_interval,
.maxlen = sizeof(dirty_writeback_interval),