From: Artem Bityutskiy <artem.bityutskiy@xxxxxxxxxxxxxxx>
The pdflush thread is long gone, however we still mention it incorrectly in the
kernel documentation. This patch fixes the situation.
Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxx>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@xxxxxxxxxxxxxxx>
---
I expect this patch to be merged via Al Viro's VFS tree.
Documentation/laptops/laptop-mode.txt | 12 ++++++------
Documentation/sysctl/vm.txt | 25 ++++++++++++++-----------
2 files changed, 20 insertions(+), 17 deletions(-)
diff --git a/Documentation/laptops/laptop-mode.txt b/Documentation/laptops/laptop-mode.txt
index 0bf25ee..4ebbfc3 100644
--- a/Documentation/laptops/laptop-mode.txt
+++ b/Documentation/laptops/laptop-mode.txt
@@ -262,9 +262,9 @@ MINIMUM_BATTERY_MINUTES=10
#
# Allowed dirty background ratio, in percent. Once DIRTY_RATIO has been
-# exceeded, the kernel will wake pdflush which will then reduce the amount
-# of dirty memory to dirty_background_ratio. Set this nice and low, so once
-# some writeout has commenced, we do a lot of it.
+# exceeded, the kernel will wake flusher threads which will then reduce the
+# amount of dirty memory to dirty_background_ratio. Set this nice and low,
+# so once some writeout has commenced, we do a lot of it.
#
#DIRTY_BACKGROUND_RATIO=5
@@ -384,9 +384,9 @@ CPU_MAXFREQ=${CPU_MAXFREQ:-'slowest'}
#
# Allowed dirty background ratio, in percent. Once DIRTY_RATIO has been
-# exceeded, the kernel will wake pdflush which will then reduce the amount
-# of dirty memory to dirty_background_ratio. Set this nice and low, so once
-# some writeout has commenced, we do a lot of it.
+# exceeded, the kernel will wake flusher threads which will then reduce the
+# amount of dirty memory to dirty_background_ratio. Set this nice and low,
+# so once some writeout has commenced, we do a lot of it.
#
DIRTY_BACKGROUND_RATIO=${DIRTY_BACKGROUND_RATIO:-'5'}
diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt
index 96f0ee8..cec12bb 100644
--- a/Documentation/sysctl/vm.txt
+++ b/Documentation/sysctl/vm.txt
@@ -77,8 +77,8 @@ huge pages although processes will also directly compact memory as required.
dirty_background_bytes
-Contains the amount of dirty memory at which the pdflush background writeback
-daemon will start writeback.
+Contains the amount of dirty memory at which the background kernel
+flusher threads will start writeback.
Note: dirty_background_bytes is the counterpart of dirty_background_ratio. Only
one of them may be specified at a time. When one sysctl is written it is
@@ -90,7 +90,7 @@ other appears as 0 when read.
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.
+the background kernel flusher threads will start writing out dirty data.
==============================================================
@@ -113,9 +113,9 @@ retained.
dirty_expire_centisecs
This tunable is used to define when dirty data is old enough to be eligible
-for writeout by the pdflush daemons. It is expressed in 100'ths of a second.
-Data which has been dirty in-memory for longer than this interval will be
-written out next time a pdflush daemon wakes up.
+for writeout by the kernel flusher threads. It is expressed in 100'ths
+of a second. Data which has been dirty in-memory for longer than this
+interval will be written out next time a flusher thread wakes up.
==============================================================
@@ -129,7 +129,7 @@ data.
dirty_writeback_centisecs
-The pdflush writeback daemons will periodically wake up and write `old' data
+The kernel flusher threads will periodically wake up and write `old' data
out to disk. This tunable expresses the interval between those wakeups, in
100'ths of a second.
@@ -428,11 +428,14 @@ See Documentation/vm/hugetlbpage.txt
nr_pdflush_threads
-The current number of pdflush threads. This value is read-only.
-The value changes according to the number of dirty pages in the system.
+This is not used by the kernel since version 2.6.32, this is read-only
+and is always set to 1. Preserve for backward-compatibility reasons.
-When necessary, additional pdflush threads are created, one per second, up to
-nr_pdflush_threads_max.
+In the past, it contained the current number of pdflush threads. The
+value changed according to the number of dirty pages in the system.
+When necessary, additional pdflush threads were created, one per second.
+However, in kernel version 2.6.32 the pdflush thread was removed in
+favour of per-block device bdi flusher threads.
==============================================================
--
1.7.10
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