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Message-ID: <49BF8BB3.1060606@vflare.org>
Date: Tue, 17 Mar 2009 17:08:27 +0530
From: Nitin Gupta <ngupta@...are.org>
To: linux-kernel@...r.kernel.org
Subject: [PATCH 3/3]: documentation
Documentation/blockdev/00-INDEX | 2 +
Documentation/blockdev/compcache.txt | 67 ++++++++++++++++++++++++++++++++++
Documentation/kernel-parameters.txt | 9 +++++
3 files changed, 78 insertions(+), 0 deletions(-)
Documentation on how to use compcache module.
Signed-off-by: Nitin Gupta <ngupta@...are.org>
---
diff --git a/Documentation/blockdev/00-INDEX b/Documentation/blockdev/00-INDEX
index 86f054c..d53dec0 100644
--- a/Documentation/blockdev/00-INDEX
+++ b/Documentation/blockdev/00-INDEX
@@ -4,6 +4,8 @@ README.DAC960
- info on Mylex DAC960/DAC1100 PCI RAID Controller Driver for Linux.
cciss.txt
- info, major/minor #'s for Compaq's SMART Array Controllers.
+compcache.txt
+ - short guide on how to setup compressed RAM swap device.
cpqarray.txt
- info on using Compaq's SMART2 Intelligent Disk Array Controllers.
floppy.txt
diff --git a/Documentation/blockdev/compcache.txt b/Documentation/blockdev/compcache.txt
new file mode 100644
index 0000000..46c33a5
--- /dev/null
+++ b/Documentation/blockdev/compcache.txt
@@ -0,0 +1,67 @@
+compcache: Compressed RAM swap device
+-------------------------------------
+
+Project home: http://code.google.com/p/compcache/
+
+This module creates RAM based block device (named ramzswap0) which acts
+as swap disk. Pages swapped to this disk are compressed and stored in
+memory itself.
+
+It uses these components:
+ - xvMalloc: memory allocator (xvmalloc.ko)
+ - LZO1X: de/compressor: (lzo_compress.ko, lzo_decompress.ko)
+
+Usage:
+ - modprobe compcache [memlimit_kb=<val>|disksize_kb=<val>] [backing_dev=<dev>]
+
+ memlimit_kb: This param is applicable only when backing_dev is given.
+ It is limit on amount compressed data stored in memory. Any
+ additional data is forwarded to backing_dev. It cannot be greater
+ than backing device size. If missing or 0, default value is used:
+ 15% of RAM or backing device size, whichever is smaller.
+
+ disksize_kb: This param is applicable only when backing_dev is not given.
+ It is limit on amount of *uncompressed* worth of data stored in
+ memory. For e.g. disksize_kb=1024 means it can hold 1024kb worth of
+ uncompressed data even if this data compresses to just, say, 100kb.
+ If missing or 0, default value is used: 25% of RAM.
+
+ backing_dev: This is block device to be used as backing store for compcache.
+ It must be a valid swap partition. We move data to this device when we
+ encounter incompressible page or memlimit is reached. TODO: we may also
+ move some pages from compcache to this device in case system is really
+ low on memory.
+ This device is not directly visible to kernel as a swap device
+ (/proc/swaps will only show /dev/ramzswap0 and not this device).
+ Managing this backing device is the job of compcache module.
+
+Examples:
+ 1) modprobe compcache memlimit_kb=10240 backing_dev=/dev/sda2
+ sets compcache limit as 10MB and /dev/sda2 as backing swap device.
+ NOTE: here /dev/sda2 is a valid swap partition.
+
+ 2) modprobe compcache backing_dev=/dev/sda2
+ same as (1) but memlimit is set to default: 15% of RAM or size of
+ backing swap device, whichever is smaller.
+
+ 3) modprobe compcache disksize_kb=10240
+ sets compcache disk size as 10MB.
+
+ 4) modprobe compcache.ko
+ same as (3) but compcache disk size will be set to default:
+ 25% of RAM size.
+
+ Once module is loaded, activate this swap with highest priority:
+ swapon /dev/ramzswap0 -p 100
+ (-p param set swap priority)
+
+Notes:
+ - compcache stats are exported via /proc/compcache
+ - If you give non-swap partition as backing_dev, nothing bad will happen -
+ swapon will simply fail to recognize /dev/ramzswap0 as swap partition.
+ So, in this case, unload the module and reload with correct backing_dev.
+
+Please report any problems to:
+
+Nitin Gupta
+ngupta@...are.org
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 54f21a5..a23f0ae 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -414,6 +414,15 @@ and is between 256 and 4096 characters. It is defined in the file
possible to determine what the correct size should be.
This option provides an override for these situations.
+ compcache.memlimit_kb=
+ See Documentation/blockdev/compcache.txt.
+
+ compcache.disksize_kb=
+ See Documentation/blockdev/compcache.txt.
+
+ compcache.backing_dev=
+ See Documentation/blockdev/compcache.txt.
+
security= [SECURITY] Choose a security module to enable at boot.
If this boot parameter is not specified, only the first
security module asking for security registration will be
--
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