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author | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 15:20:36 -0700 |
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committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 15:20:36 -0700 |
commit | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch) | |
tree | 0bba044c4ce775e45a88a51686b5d9f90697ea9d /Documentation/sysctl/vm.txt | |
download | kernel_samsung_smdk4412-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.zip kernel_samsung_smdk4412-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.gz kernel_samsung_smdk4412-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.bz2 |
Linux-2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Diffstat (limited to 'Documentation/sysctl/vm.txt')
-rw-r--r-- | Documentation/sysctl/vm.txt | 104 |
1 files changed, 104 insertions, 0 deletions
diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt new file mode 100644 index 0000000..2f1aae3 --- /dev/null +++ b/Documentation/sysctl/vm.txt @@ -0,0 +1,104 @@ +Documentation for /proc/sys/vm/* kernel version 2.2.10 + (c) 1998, 1999, Rik van Riel <riel@nl.linux.org> + +For general info and legal blurb, please look in README. + +============================================================== + +This file contains the documentation for the sysctl files in +/proc/sys/vm and is valid for Linux kernel version 2.2. + +The files in this directory can be used to tune the operation +of the virtual memory (VM) subsystem of the Linux kernel and +the writeout of dirty data to disk. + +Default values and initialization routines for most of these +files can be found in mm/swap.c. + +Currently, these files are in /proc/sys/vm: +- overcommit_memory +- page-cluster +- dirty_ratio +- dirty_background_ratio +- dirty_expire_centisecs +- dirty_writeback_centisecs +- max_map_count +- min_free_kbytes +- laptop_mode +- block_dump + +============================================================== + +dirty_ratio, dirty_background_ratio, dirty_expire_centisecs, +dirty_writeback_centisecs, vfs_cache_pressure, laptop_mode, +block_dump, swap_token_timeout: + +See Documentation/filesystems/proc.txt + +============================================================== + +overcommit_memory: + +This value contains a flag that enables memory overcommitment. + +When this flag is 0, the kernel attempts to estimate the amount +of free memory left when userspace requests more memory. + +When this flag is 1, the kernel pretends there is always enough +memory until it actually runs out. + +When this flag is 2, the kernel uses a "never overcommit" +policy that attempts to prevent any overcommit of memory. + +This feature can be very useful because there are a lot of +programs that malloc() huge amounts of memory "just-in-case" +and don't use much of it. + +The default value is 0. + +See Documentation/vm/overcommit-accounting and +security/commoncap.c::cap_vm_enough_memory() for more information. + +============================================================== + +overcommit_ratio: + +When overcommit_memory is set to 2, the committed address +space is not permitted to exceed swap plus this percentage +of physical RAM. See above. + +============================================================== + +page-cluster: + +The Linux VM subsystem avoids excessive disk seeks by reading +multiple pages on a page fault. The number of pages it reads +is dependent on the amount of memory in your machine. + +The number of pages the kernel reads in at once is equal to +2 ^ page-cluster. Values above 2 ^ 5 don't make much sense +for swap because we only cluster swap data in 32-page groups. + +============================================================== + +max_map_count: + +This file contains the maximum number of memory map areas a process +may have. Memory map areas are used as a side-effect of calling +malloc, directly by mmap and mprotect, and also when loading shared +libraries. + +While most applications need less than a thousand maps, certain +programs, particularly malloc debuggers, may consume lots of them, +e.g., up to one or two maps per allocation. + +The default value is 65536. + +============================================================== + +min_free_kbytes: + +This is used to force the Linux VM to keep a minimum number +of kilobytes free. The VM uses this number to compute a pages_min +value for each lowmem zone in the system. Each lowmem zone gets +a number of reserved free pages based proportionally on its size. |