[lc-checkins] CVS: linux/Documentation Configure.help,1.7,1.8

[Rodrigo S. de C. <rc...@us...>]

Update of /cvsroot/linuxcompressed/linux/Documentation
In directory usw-pr-cvs1:/tmp/cvs-serv13268/Documentation

Modified Files:
	Configure.help 
Log Message:
Feature
o Implemented support for resizing the compressed cache on demand. The
user defines the maximum compressed cache size and compressed cache
will grow up to this size if necessary. Only then it will start
swapping out fragments. And when the compressed cache entries start to
get empty, their pages will be released to the system, decreasing
compressed cache size. Still have to solve some issues about resizing
vswap.

o Changed most of the calls from comp_cache_free_locked() to
comp_cache_free(), in order to release the page if necessary. Only
calls from writeout functions were not changed since we don't want to
use those pages to shrink the compressed cache.

Bug fixes
o Fixed potential oops in comp_cache_use_address(). If the ptes cannot
be set to the new address, we would access a null variable (fragment).

o Fixed bug in swap in process for virtual swap addresses. While
allocating a new page, that virtual swap address might get unused (it
gained a real address or vswap table got shrunk), what could lead to a
BUG() in comp_cache_swp_duplicate().

Other
o Some comments added to functions in adaptivity.c
o Updated Configure.help for CONFIG_COMP_CACHE



Index: Configure.help
===================================================================
RCS file: /cvsroot/linuxcompressed/linux/Documentation/Configure.help,v
retrieving revision 1.7
retrieving revision 1.8
diff -C2 -r1.7 -r1.8
*** Configure.help	20 Jun 2002 14:28:48 -0000	1.7
--- Configure.help	25 Jun 2002 14:34:07 -0000	1.8
***************
*** 387,391 ****
  
    Initial number of pages reserved for compressed cache is set by the
!   kernel parameter "compsize=N", where N is a number of memory pages.
  
    If unsure, say N here.
--- 387,393 ----
  
    Initial number of pages reserved for compressed cache is set by the
!   kernel parameter "compsize=N", where N is a memory size like the
!   input accepted by "mem=" parameter. For example "compsize=48M" sets
!   the initial compressed cache size to 48 megabytes.
  
    If unsure, say N here.
***************
*** 398,401 ****
--- 400,425 ----
    behaviour. If you don't select this option, compressed cache will
    store only anonymous pages, ie pages not mapped to files.
+ 
+   If unsure, say N here.
+ 
+ Resize Compressed Cache On Demand
+ CONFIG_COMP_DEMAND_RESIZE
+ 
+   Select this option in case you want compressed cache to start with a
+   minimum number of pages and resize on demand. It means that
+   compressed cache will grow uo to its maximum size while the system
+   is under memory pressure and will only start swapping out when it
+   reaches that size. As soon as the reserved pages for compressed
+   cache are no longer used, they are freed to the system, decreasing
+   compressed cache size.
+ 
+   The maximum size is defined by the very same kernel parameter
+   "compsize=N", where N is a memory size like the input accepted by
+   "mem=" parameter. For example "compsize=48M" will set the maximum
+   compressed cache size to 48 megabytes.
+ 
+   In the case this option is enabled, the user cannot any longer
+   change compressed cache size via sysctl entry
+   (/proc/sys/vm/comp_cache/size).
  
    If unsure, say N here.