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Date: Mon, 30 Mar 2009 20:24:32 +0530 From: Nitin Gupta <nitingupta910@...il.com> To: Andrew Morton <akpm@...ux-foundation.org> CC: Pekka Enberg <penberg@...helsinki.fi>, Christoph Lameter <cl@...ux-foundation.org>, Ed Tomlinson <edt@....ca>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> Subject: [PATCH 3/3] ramzswap documentation Documentation/blockdev/00-INDEX | 2 + Documentation/blockdev/ramzswap.txt | 67 +++++++++++++++++++++++++++++++++++ Documentation/kernel-parameters.txt | 9 +++++ 3 files changed, 78 insertions(+), 0 deletions(-) Documentation on how to use ramzswap module. Signed-off-by: Nitin Gupta <ngupta@...are.org> --- diff --git a/Documentation/blockdev/00-INDEX b/Documentation/blockdev/00-INDEX index 86f054c..8751488 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. +ramzswap.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/ramzswap.txt b/Documentation/blockdev/ramzswap.txt new file mode 100644 index 0000000..835afcf --- /dev/null +++ b/Documentation/blockdev/ramzswap.txt @@ -0,0 +1,67 @@ +ramzswap: Compressed RAM swap device +------------------------------------ + +Project home: http://compcache.googlecode.com + +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 ramzswap [memlimit_kb=<val>|disksize_kb=<val>] [backing_swap=<dev>] + + memlimit_kb: This param is applicable only when backing_swap is given. + It is limit on amount compressed data stored in memory. Any + additional data is forwarded to backing_swap. 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_swap 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_swap: This is block device to be used as backing store for ramzswap. + 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 ramzswap 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 ramzswap module. + +Examples: + 1) modprobe ramzswap memlimit_kb=10240 backing_swap=/dev/sda2 + sets ramzswap limit as 10MB and /dev/sda2 as backing swap device. + NOTE: here /dev/sda2 is a valid swap partition. + + 2) modprobe ramzswap backing_swap=/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 ramzswap disksize_kb=10240 + sets ramzswap disk size as 10MB. + + 4) modprobe ramzswap.ko + same as (3) but ramzswap 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: + - ramzswap stats are exported via /proc/ramzswap + - If you give non-swap partition as backing_swap, 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_swap. + +Please report any problems to: + +Nitin Gupta +ngupta@...are.org diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index be3bde5..1cb1d2e 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -415,6 +415,15 @@ 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. + ramzswap.memlimit_kb= + See Documentation/blockdev/ramzswap.txt. + + ramzswap.disksize_kb= + See Documentation/blockdev/ramzswap.txt. + + ramzswap.backing_swap= + See Documentation/blockdev/ramzswap.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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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