The patch titled
mm: add dirty_highmem option
has been added to the -mm tree. Its filename is
mm-add-dirty_highmem-option.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: mm: add dirty_highmem option
From: Bron Gondwana <brong@xxxxxxxxxxx>
A 32 bit machine with HIGHMEM64 enabled running DCC has an MMAPed file of
approximately 2Gb size which contains a hash format that is written
"randomly" by the dbclean process. On 2.6.16 this process took a few
minutes. With lowmem only accounting of dirty ratios, this takes about 12
hours of 100% disk IO, all random writes.
This patch includes some code cleanup from Linus and a toggle in
/proc/sys/vm/dirty_highmem which can be set to 1 to add the highmem back to
the total available memory count.
Signed-off-by: Bron Gondwana <brong@xxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: WU Fengguang <wfg@xxxxxxxxxxxxxxxx>
Cc: Ethan Solomita <solo@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/filesystems/proc.txt | 12 ++++++++++++
Documentation/sysctl/vm.txt | 9 +++++----
include/linux/writeback.h | 1 +
kernel/sysctl.c | 16 +++++++++++++++-
mm/page-writeback.c | 9 ++++++++-
5 files changed, 41 insertions(+), 6 deletions(-)
diff -puN Documentation/filesystems/proc.txt~mm-add-dirty_highmem-option Documentation/filesystems/proc.txt
--- a/Documentation/filesystems/proc.txt~mm-add-dirty_highmem-option
+++ a/Documentation/filesystems/proc.txt
@@ -1258,6 +1258,18 @@ dirty_background_ratio
Contains, as a percentage of total system memory, the number of pages at which
the pdflush background writeback daemon will start writing out dirty data.
+dirty_highmem
+-------------
+
+Contains, as a boolean, a switch to allow highmem to be counted as
+part of the "available" memory against which the dirty ratios will be
+applied.
+
+Setting this to 1 can be useful on 32 bit machines where you want to make
+random changes within an MMAPed file that is larger than your available
+lowmem, however it is potentially dangerous and has serious bounce-buffer
+issues.
+
dirty_ratio
-----------------
diff -puN Documentation/sysctl/vm.txt~mm-add-dirty_highmem-option Documentation/sysctl/vm.txt
--- a/Documentation/sysctl/vm.txt~mm-add-dirty_highmem-option
+++ a/Documentation/sysctl/vm.txt
@@ -18,6 +18,7 @@ files can be found in mm/swap.c.
Currently, these files are in /proc/sys/vm:
- overcommit_memory
- page-cluster
+- dirty_highmem
- dirty_ratio
- dirty_background_ratio
- dirty_expire_centisecs
@@ -37,10 +38,10 @@ Currently, these files are in /proc/sys/
==============================================================
-dirty_ratio, dirty_background_ratio, dirty_expire_centisecs,
-dirty_writeback_centisecs, vfs_cache_pressure, laptop_mode,
-block_dump, swap_token_timeout, drop-caches,
-hugepages_treat_as_movable:
+dirty_highmem, dirty_ratio, dirty_background_ratio,
+dirty_expire_centisecs, dirty_writeback_centisecs,
+vfs_cache_pressure, laptop_mode, block_dump,
+swap_token_timeout, drop-caches, hugepages_treat_as_movable:
See Documentation/filesystems/proc.txt
diff -puN include/linux/writeback.h~mm-add-dirty_highmem-option include/linux/writeback.h
--- a/include/linux/writeback.h~mm-add-dirty_highmem-option
+++ a/include/linux/writeback.h
@@ -98,6 +98,7 @@ void throttle_vm_writeout(gfp_t gfp_mask
/* These are exported to sysctl. */
extern int dirty_background_ratio;
+extern int vm_dirty_highmem;
extern int vm_dirty_ratio;
extern int dirty_writeback_interval;
extern int dirty_expire_interval;
diff -puN kernel/sysctl.c~mm-add-dirty_highmem-option kernel/sysctl.c
--- a/kernel/sysctl.c~mm-add-dirty_highmem-option
+++ a/kernel/sysctl.c
@@ -82,9 +82,10 @@ extern int maps_protect;
extern int sysctl_stat_interval;
extern int audit_argv_kb;
+static int one = 1;
+
/* Constants used for minimum and maximum */
#ifdef CONFIG_DETECT_SOFTLOCKUP
-static int one = 1;
static int sixty = 60;
#endif
@@ -1081,6 +1082,19 @@ static struct ctl_table vm_table[] = {
.extra1 = &zero,
},
#endif
+#ifdef CONFIG_HIGHMEM
+ {
+ .ctl_name = CTL_UNNUMBERED,
+ .procname = "dirty_highmem",
+ .data = &vm_dirty_highmem,
+ .maxlen = sizeof(vm_dirty_highmem),
+ .mode = 0644,
+ .proc_handler = &proc_dointvec_minmax,
+ .strategy = &sysctl_intvec,
+ .extra1 = &zero,
+ .extra2 = &one,
+ },
+#endif
/*
* NOTE: do not add new entries to this table unless you have read
* Documentation/sysctl/ctl_unnumbered.txt
diff -puN mm/page-writeback.c~mm-add-dirty_highmem-option mm/page-writeback.c
--- a/mm/page-writeback.c~mm-add-dirty_highmem-option
+++ a/mm/page-writeback.c
@@ -69,6 +69,12 @@ static inline long sync_writeback_pages(
int dirty_background_ratio = 5;
/*
+ * free highmem will not be subtracted from the total free memory
+ * for calculating free ratios if vm_dirty_highmem is true
+ */
+int vm_dirty_highmem;
+
+/*
* The generator of dirty data starts writeback at this percentage
*/
int vm_dirty_ratio = 10;
@@ -287,7 +293,8 @@ static unsigned long determine_dirtyable
x = global_page_state(NR_FREE_PAGES)
+ global_page_state(NR_INACTIVE)
+ global_page_state(NR_ACTIVE);
- x -= highmem_dirtyable_memory(x);
+ if (!vm_dirty_highmem)
+ x -= highmem_dirtyable_memory(x);
return x + 1; /* Ensure that we never return 0 */
}
_
Patches currently in -mm which might be from brong@xxxxxxxxxxx are
mm-add-dirty_highmem-option.patch
mm-add-dirty_highmem-option-fix.patch
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