Re: [2.4] heavy-load under swap space shortage

[Marcelo Tosatti]

On Wed, May 26, 2004 at 08:24:34PM +0200, Marc-Christian Petersen wrote:
> On Wednesday 26 May 2004 14:41, Marcelo Tosatti wrote:
> 
> Marcelo,
> 
> > I think we can merge this patch.
> 
> I think this too =)
> 
> 
> > Its very safe - default behaviour unchanged.
> > Jun, are you willing to do another test for us if this gets merged
> > in v2.4.27-pre4 ?
> > Maybe we should document the VM tunables somewhere outside source code
> > (Documentation/) ?
> 
> I think we should merge the attached patches to finally remove utterly bogus 
> and non-existent documentation things and clean up stuff a bit and document 
> the -aa VM bits.
> 
> Agreed?
>
> Kinda same cleanups and more following soon for 2.6-mm.

Hi Marc, 

Looks ok for v2.4 -- would be good if Rik and Andrea
could go over it as well.

> --- a/Documentation/sysctl/vm.txt	2004-05-26 19:57:15.000000000 +0200
> +++ b/Documentation/sysctl/vm.txt	2004-05-26 20:06:20.000000000 +0200
> @@ -1,111 +1,143 @@
> -Documentation for /proc/sys/vm/*	kernel version 2.4.19
> -	(c) 1998, 1999,  Rik van Riel <riel@xxxxxxxxxxxx>
> +Documentation for /proc/sys/vm/*	Kernel version 2.4.26
> +=============================================================
>  
> -For general info and legal blurb, please look in README.
> + (c) 1998, 1999, Rik van Riel <riel@xxxxxxxxxxxx>
> +    - Initial version
>  
> -==============================================================
> + (c) 2004, Marc-Christian Petersen <m.c.p@xxxxxxxxxxxxxxxxx>
> +    - Removed non-existent knobs which were removed in early
> +      2.4 stages
> +    - Corrected values for bdflush
> +    - Documented missing tunables
> +    - Documented aa-vm tunables
> +
> +
> +
> +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 2.4.
> +/proc/sys/vm and is valid for Linux kernel v2.4.26.
>  
>  The files in this directory can be used to tune the operation
>  of the virtual memory (VM) subsystem of the Linux kernel, and
> -one of the files (bdflush) also has a little influence on disk
> -usage.
> +three of the files (bdflush, max-readahead, min-readahead)
> +also have some influence on disk usage.
>  
>  Default values and initialization routines for most of these
> -files can be found in mm/swap.c.
> +files can be found in mm/vmscan.c, mm/page_alloc.c and
> +mm/filemap.c.
>  
>  Currently, these files are in /proc/sys/vm:
>  - bdflush
> +- block_dump
>  - kswapd
> +- laptop_mode
> +- max-readahead
> +- min-readahead
>  - max_map_count
>  - overcommit_memory
>  - page-cluster
>  - pagetable_cache
> +- vm_anon_lru
> +- vm_cache_scan_ratio
> +- vm_gfp_debug
> +- vm_lru_balance_ratio
> +- vm_mapped_ratio
> +- vm_passes
> +- vm_vfs_scan_ratio
> +=============================================================
>  
> -==============================================================
>  
> -bdflush:
>  
> +bdflush:
> +--------
>  This file controls the operation of the bdflush kernel
>  daemon. The source code to this struct can be found in
> -linux/fs/buffer.c. It currently contains 9 integer values,
> +fs/buffer.c. It currently contains 9 integer values,
>  of which 6 are actually used by the kernel.
>  
> -From linux/fs/buffer.c:
> ---------------------------------------------------------------
> -union bdflush_param {
> -	struct {
> -		int nfract;	/* Percentage of buffer cache dirty to
> -				   activate bdflush */
> -		int ndirty;	/* Maximum number of dirty blocks to write out per
> -				   wake-cycle */
> -		int dummy2;	/* old "nrefill" */
> -		int dummy3;	/* unused */
> -		int interval;	/* jiffies delay between kupdate flushes */
> -		int age_buffer;	/* Time for normal buffer to age before we flush it */
> -		int nfract_sync;/* Percentage of buffer cache dirty to
> -				   activate bdflush synchronously */
> -		int nfract_stop_bdflush; /* Percentage of buffer cache dirty to stop bdflush */
> -		int dummy5;	/* unused */
> -	} b_un;
> -	unsigned int data[N_PARAM];
> -} bdf_prm = {{30, 500, 0, 0, 5*HZ, 30*HZ, 60, 20, 0}};
> ---------------------------------------------------------------
> -
> -int nfract:
> -The first parameter governs the maximum number of dirty
> -buffers in the buffer cache. Dirty means that the contents
> -of the buffer still have to be written to disk (as opposed
> -to a clean buffer, which can just be forgotten about).
> -Setting this to a high value means that Linux can delay disk
> -writes for a long time, but it also means that it will have
> -to do a lot of I/O at once when memory becomes short. A low
> -value will spread out disk I/O more evenly, at the cost of
> -more frequent I/O operations.  The default value is 30%,
> -the minimum is 0%, and the maximum is 100%.
> -
> -int ndirty:
> -The second parameter (ndirty) gives the maximum number of
> -dirty buffers that bdflush can write to the disk in one time.
> -A high value will mean delayed, bursty I/O, while a small
> -value can lead to memory shortage when bdflush isn't woken
> -up often enough.
> -
> -int interval:
> -The fifth parameter, interval, is the minimum rate at
> -which kupdate will wake and flush.  The value is expressed in
> -jiffies (clockticks), the number of jiffies per second is
> -normally 100 (Alpha is 1024). Thus, x*HZ is x seconds.  The
> -default value is 5 seconds, the minimum is 0 seconds, and the
> -maximum is 600 seconds.
> -
> -int age_buffer:
> -The sixth parameter, age_buffer, governs the maximum time
> -Linux waits before writing out a dirty buffer to disk.  The
> -value is in jiffies.  The default value is 30 seconds,
> -the minimum is 1 second, and the maximum 6,000 seconds.
> -
> -int nfract_sync:
> -The seventh parameter, nfract_sync, governs the percentage
> -of buffer cache that is dirty before bdflush activates
> -synchronously.  This can be viewed as the hard limit before
> -bdflush forces buffers to disk.  The default is 60%, the
> -minimum is 0%, and the maximum is 100%.
> -
> -int nfract_stop_bdflush:
> -The eighth parameter, nfract_stop_bdflush, governs the percentage
> -of buffer cache that is dirty which will stop bdflush.
> -The default is 20%, the miniumum is 0%, and the maxiumum is 100%.
> -==============================================================
> +nfract:		The first parameter governs the maximum
> +		number of dirty buffers in the buffer
> +		cache. Dirty means that the contents of the
> +		buffer still have to be written to disk (as
> +		opposed to a clean buffer, which can just be
> +		forgotten about). Setting this to a high
> +		value means that Linux can delay disk writes
> +		for a long time, but it also means that it
> +		will have to do a lot of I/O at once when
> +		memory becomes short. A low value will
> +		spread out disk I/O more evenly, at the cost
> +		of more frequent I/O operations. The default
> +		value is 30%, the minimum is 0%, and the
> +		maximum is 100%.
> +
> +ndirty:		The second parameter (ndirty) gives the
> +		maximum number of dirty buffers that bdflush
> +		can write to the disk in one time. A high
> +		value will mean delayed, bursty I/O, while a
> +		small value can lead to memory shortage when
> +		bdflush isn't woken up often enough. The
> +		default value is 500 dirty buffers, the
> +		minimum is 1, and the maximum is 50000.
> +
> +dummy2:		The third parameter is not used.
> +
> +dummy3:		The fourth parameter is not used.
> +
> +interval:	The fifth parameter, interval, is the minimum
> +		rate at which kupdate will wake and flush.
> +		The value is in jiffies (clockticks), the
> +		number of jiffies per second is normally 100
> +		(Alpha is 1024). Thus, x*HZ is x seconds. The
> +		default value is 5 seconds, the minimum	is 0
> +		seconds, and the maximum is 10,000 seconds.
> +
> +age_buffer:	The sixth parameter, age_buffer, governs the
> +		maximum time Linux waits before writing out a
> +		dirty buffer to disk. The value is in jiffies.
> +		The default value is 30 seconds, the minimum
> +		is 1 second, and the maximum 10,000 seconds.
> +
> +sync:		The seventh parameter, nfract_sync, governs
> +		the percentage of buffer cache that is dirty
> +		before bdflush activates synchronously. This
> +		can be viewed as the hard limit before
> +		bdflush forces buffers to disk. The default
> +		is 60%,	the minimum is 0%, and the maximum
> +		is 100%.
> +
> +stop_bdflush:	The eighth parameter, nfract_stop_bdflush,
> +		governs the percentage of buffer cache that
> +		is dirty which will stop bdflush. The default
> +		is 20%, the miniumum is 0%, and the maxiumum
> +		is 100%.
> +
> +dummy5:		The ninth parameter is not used.
> +
> +So the default is: 30 500 0 0 500 3000 60 20 0   for 100 HZ.
> +=============================================================
> +
> +
> +
> +block_dump:
> +-----------
> +It can happen that the disk still keeps spinning up and you
> +don't quite know why or what causes it. The laptop mode patch
> +has a little helper for that as well. When set to 1, it will
> +dump info to the kernel message buffer about what process
> +caused the io. Be careful when playing with this setting.
> +It is advisable to shut down syslog first! The default is 0.
> +=============================================================
> +
>  
> -kswapd:
>  
> +kswapd:
> +-------
>  Kswapd is the kernel swapout daemon. That is, kswapd is that
>  piece of the kernel that frees memory when it gets fragmented
> -or full. Since every system is different, you'll probably want
> -some control over this piece of the system.
> +or full. Since every system is different, you'll probably
> +want some control over this piece of the system.
>  
>  The numbers in this page correspond to the numbers in the
>  struct pager_daemon {tries_base, tries_min, swap_cluster
> @@ -117,39 +149,83 @@ tries_base	The maximum number of pages k
>  		number. Usually this number will be divided
>  		by 4 or 8 (see mm/vmscan.c), so it isn't as
>  		big as it looks.
> -		When you need to increase the bandwidth to/from
> -		swap, you'll want to increase this number.
> +		When you need to increase the bandwidth to/
> +		from swap, you'll want to increase this
> +		number.
> +
>  tries_min	This is the minimum number of times kswapd
>  		tries to free a page each time it is called.
>  		Basically it's just there to make sure that
>  		kswapd frees some pages even when it's being
>  		called with minimum priority.
> +
>  swap_cluster	This is the number of pages kswapd writes in
>  		one turn. You want this large so that kswapd
>  		does it's I/O in large chunks and the disk
> -		doesn't have to seek often, but you don't want
> -		it to be too large since that would flood the
> -		request queue.
> +		doesn't have to seek often, but you don't
> +		want it to be too large since that would
> +		flood the request queue.
> +
> +The default value is: 512 32 8.
> +=============================================================
>  
> -==============================================================
>  
> -overcommit_memory:
>  
> -This value contains a flag that enables memory overcommitment.
> -When this flag is 0, the kernel checks before each malloc()
> -to see if there's enough memory left. If the flag is nonzero,
> -the system pretends there's always enough memory.
> +laptop_mode:
> +------------
> +Setting this to 1 switches the vm (and block layer) to laptop
> +mode. Leaving it to 0 makes the kernel work like before. When
> +in laptop mode, you also want to extend the intervals
> +desribed in Documentation/laptop-mode.txt.
> +See the laptop-mode.sh script for how to do that.
> +
> +The default value is 0.
> +=============================================================
>  
> -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.
>  
> -Look at: mm/mmap.c::vm_enough_memory() for more information.
>  
> -==============================================================
> +max-readahead:
> +--------------
> +This tunable affects how early the Linux VFS will fetch the
> +next block of a file from memory. File readahead values are
> +determined on a per file basis in the VFS and are adjusted
> +based on the behavior of the application accessing the file.
> +Anytime the current position being read in a file plus the
> +current read ahead value results in the file pointer pointing
> +to the next block in the file, that block will be fetched
> +from disk. By raising this value, the Linux kernel will allow
> +the readahead value to grow larger, resulting in more blocks
> +being prefetched from disks which predictably access files in
> +uniform linear fashion. This can result in performance
> +improvements, but can also result in excess (and often
> +unnecessary) memory usage. Lowering this value has the
> +opposite affect. By forcing readaheads to be less aggressive,
> +memory may be conserved at a potential performance impact.
> +
> +The default value is 31.
> +=============================================================
>  
> -max_map_count:
>  
> +
> +min-readahead:
> +--------------
> +Like max-readahead, min-readahead places a floor on the
> +readahead value. Raising this number forces a files readahead
> +value to be unconditionally higher, which can bring about
> +performance improvements, provided that all file access in
> +the system is predictably linear from the start to the end of
> +a file. This of course results in higher memory usage from
> +the pagecache. Conversely, lowering this value, allows the
> +kernel to conserve pagecache memory, at a potential
> +performance cost.
> +
> +The default value is 3.
> +=============================================================
> +
> +
> +
> +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
> @@ -159,10 +235,29 @@ While most applications need less than a
>  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.
> +=============================================================
> +
> +
> +
> +overcommit_memory:
> +------------------
> +This value contains a flag to enable memory overcommitment.
> +When this flag is 0, the kernel checks before each malloc()
> +to see if there's enough memory left. If the flag is nonzero,
> +the system pretends there's always enough 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.
> +
> +Look at: mm/mmap.c::vm_enough_memory() for more information.
> +=============================================================
> +
>  
> -page-cluster:
>  
> +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.
> @@ -170,11 +265,12 @@ is dependent on the amount of memory in 
>  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.
> +=============================================================
>  
> -==============================================================
>  
> -pagetable_cache:
>  
> +pagetable_cache:
> +----------------
>  The kernel keeps a number of page tables in a per-processor
>  cache (this helps a lot on SMP systems). The cache size for
>  each processor will be between the low and the high value.
> @@ -188,3 +284,98 @@ For large systems, the settings are prob
>  systems they won't hurt a bit. For small systems (<16MB ram)
>  it might be advantageous to set both values to 0.
>  
> +The default value is: 25 50.
> +=============================================================
> +
> +
> +
> +vm_anon_lru:
> +------------
> +select if to immdiatly insert anon pages in the lru.
> +Immediatly means as soon as they're allocated during the page
> +faults. If this is set to 0, they're inserted only after the
> +first swapout.
> +  
> +Having anon pages immediatly inserted in the lru allows the
> +VM to know better when it's worthwhile to start swapping
> +anonymous ram, it will start to swap earlier and it should
> +swap smoother and faster, but it will decrease scalability
> +on the >16-ways of an order of magnitude. Big SMP/NUMA
> +definitely can't take an hit on a global spinlock at
> +every anon page allocation.
> +
> +Low ram machines that swaps all the time want to turn
> +this on (i.e. set to 1).
> +
> +The default value is 1.
> +=============================================================
> +
> +
> +
> +vm_cache_scan_ratio:
> +--------------------
> +is how much of the inactive LRU queue we will scan in one go.
> +A value of 6 for vm_cache_scan_ratio implies that we'll scan
> +1/6 of the inactive lists during a normal aging round.
> +
> +The default value is 6.
> +=============================================================
> +
> +
> +
> +vm_gfp_debug:
> +------------
> +is when __alloc_pages fails, dump us a stack. This will
> +mostly happen during OOM conditions (hopefully ;)
> +
> +The default value is 0.
> +=============================================================
> +
> +
> +
> +vm_lru_balance_ratio:
> +---------------------
> +controls the balance between active and inactive cache. The
> +bigger vm_balance is, the easier the active cache will grow,
> +because we'll rotate the active list slowly. A value of 2
> +means we'll go towards a balance of 1/3 of the cache being
> +inactive.
> +
> +The default value is 2.
> +=============================================================
> +
> +
> +
> +vm_mapped_ratio:
> +----------------
> +controls the pageout rate, the smaller, the earlier we'll
> +start to pageout.
> +
> +The default value is 100.
> +=============================================================
> +
> +
> +
> +vm_passes:
> +----------
> +is the number of vm passes before failing the memory
> +balancing. Take into account 3 passes are needed for a
> +flush/wait/free cycle and that we only scan
> +1/vm_cache_scan_ratio of the inactive list at each pass.
> +
> +The default value is 60.
> +=============================================================
> +
> +
> +
> +vm_vfs_scan_ratio:
> +------------------
> +is what proportion of the VFS queues we will scan in one go.
> +A value of 6 for vm_vfs_scan_ratio implies that 1/6th of the
> +unused-inode, dentry and dquot caches will be freed during a
> +normal aging round.
> +Big fileservers (NFS, SMB etc.) probably want to set this
> +value to 3 or 2.
> +
> +The default value is 6.
> +=============================================================
> --- a/Documentation/filesystems/proc.txt	2004-05-23 00:08:31.000000000 +0200
> +++ b/Documentation/filesystems/proc.txt	2004-05-23 02:33:41.000000000 +0200
> @@ -936,172 +936,7 @@ program to load modules on demand.
>  
>  2.4 /proc/sys/vm - The virtual memory subsystem
>  -----------------------------------------------
> -
> -The files  in  this directory can be used to tune the operation of the virtual
> -memory (VM)  subsystem  of  the  Linux  kernel.  In addition, one of the files
> -(bdflush) has some influence on disk usage.
> -
> -bdflush
> --------
> -
> -This file  controls  the  operation of the bdflush kernel daemon. It currently
> -contains nine  integer  values,  six of which are actually used by the kernel.
> -They are listed in table 2-2.
> -
> -
> -Table 2-2: Parameters in /proc/sys/vm/bdflush 
> -..............................................................................
> - Value      Meaning                                                            
> - nfract     Percentage of buffer cache dirty to activate bdflush              
> - ndirty     Maximum number of dirty blocks to  write out per wake-cycle        
> - dummy      Unused                                                             
> - dummy      Unused                                                             
> - interval   jiffies delay between kupdate flushes
> - age_buffer Time for normal buffer to age before we flush it                   
> - nfract_sync Percentage of buffer cache dirty to activate bdflush synchronously
> - nfract_stop_bdflush Percetange of buffer cache dirty to stop bdflush
> - dummy      Unused                                                             
> -..............................................................................
> -
> -nfract
> -------
> -
> -This parameter  governs  the  maximum  number  of  dirty buffers in the buffer
> -cache. Dirty means that the contents of the buffer still have to be written to
> -disk (as  opposed  to  a  clean  buffer,  which  can just be forgotten about).
> -Setting this  to  a  higher value means that Linux can delay disk writes for a
> -long time, but it also means that it will have to do a lot of I/O at once when
> -memory becomes short. A lower value will spread out disk I/O more evenly.
> -
> -interval
> ---------
> -
> -The interval between two kupdate runs. The value is expressed in
> -jiffies (clockticks),  the  number of jiffies per second is 100.
> -
> -ndirty
> -------
> -
> -Ndirty gives the maximum number of dirty buffers that bdflush can write to the
> -disk at  one  time.  A high value will mean delayed, bursty I/O, while a small
> -value can lead to memory shortage when bdflush isn't woken up often enough.
> -
> -age_buffer
> -----------
> -
> -Finally, the age_buffer parameter govern the maximum time Linux
> -waits before  writing  out  a  dirty buffer to disk. The value is expressed in
> -jiffies (clockticks),  the  number of jiffies per second is 100.
> -
> -nfract_sync
> ------------
> -
> -nfract_stop_bdflush
> --------------------
> -
> -kswapd
> -------
> -
> -Kswapd is  the  kernel  swap  out daemon. That is, kswapd is that piece of the
> -kernel that  frees  memory when it gets fragmented or full. Since every system
> -is different, you'll probably want some control over this piece of the system.
> -
> -The file contains three numbers:
> -
> -tries_base
> -----------
> -
> -The maximum  number  of  pages kswapd tries to free in one round is calculated
> -from this  number.  Usually  this  number  will  be  divided  by  4  or 8 (see
> -mm/vmscan.c), so it isn't as big as it looks.
> -
> -When you  need to increase the bandwidth to/from swap, you'll want to increase
> -this number.
> -
> -tries_min
> ----------
> -
> -This is  the  minimum number of times kswapd tries to free a page each time it
> -is called. Basically it's just there to make sure that kswapd frees some pages
> -even when it's being called with minimum priority.
> -
> -overcommit_memory
> ------------------
> -
> -This file  contains  one  value.  The following algorithm is used to decide if
> -there's enough  memory:  if  the  value of overcommit_memory is positive, then
> -there's always  enough  memory. This is a useful feature, since programs often
> -malloc() huge  amounts  of  memory 'just in case', while they only use a small
> -part of  it.  Leaving  this value at 0 will lead to the failure of such a huge
> -malloc(), when in fact the system has enough memory for the program to run.
> -
> -On the  other  hand,  enabling this feature can cause you to run out of memory
> -and thrash the system to death, so large and/or important servers will want to
> -set this value to 0.
> -
> -pagetable_cache
> ----------------
> -
> -The kernel  keeps a number of page tables in a per-processor cache (this helps
> -a lot  on  SMP systems). The cache size for each processor will be between the
> -low and the high value.
> -
> -On a  low-memory,  single  CPU system, you can safely set these values to 0 so
> -you don't  waste  memory.  It  is  used  on SMP systems so that the system can
> -perform fast  pagetable allocations without having to acquire the kernel memory
> -lock.
> -
> -For large  systems,  the  settings  are probably fine. For normal systems they
> -won't hurt  a  bit.  For  small  systems  (  less  than  16MB ram) it might be
> -advantageous to set both values to 0.
> -
> -swapctl
> --------
> -
> -This file  contains  no less than 8 variables. All of these values are used by
> -kswapd.
> -
> -The first four variables
> -* sc_max_page_age,
> -* sc_page_advance,
> -* sc_page_decline and
> -* sc_page_initial_age
> -are used  to  keep  track  of  Linux's page aging. Page aging is a bookkeeping
> -method to  track  which pages of memory are often used, and which pages can be
> -swapped out without consequences.
> -
> -When a  page  is  swapped in, it starts at sc_page_initial_age (default 3) and
> -when the  page  is  scanned  by  kswapd,  its age is adjusted according to the
> -following scheme:
> -
> -* If  the  page  was used since the last time we scanned, its age is increased
> -  by sc_page_advance  (default  3).  Where  the  maximum  value  is  given  by
> -  sc_max_page_age (default 20).
> -* Otherwise  (meaning  it wasn't used) its age is decreased by sc_page_decline
> -  (default 1).
> -
> -When a page reaches age 0, it's ready to be swapped out.
> -
> -The variables  sc_age_cluster_fract, sc_age_cluster_min, sc_pageout_weight and
> -sc_bufferout_weight, can  be  used  to  control  kswapd's  aggressiveness  in
> -swapping out pages.
> -
> -Sc_age_cluster_fract is used to calculate how many pages from a process are to
> -be scanned by kswapd. The formula used is
> -
> -(sc_age_cluster_fract divided by 1024) times resident set size
> -
> -So if you want kswapd to scan the whole process, sc_age_cluster_fract needs to
> -have a  value  of  1024.  The  minimum  number  of  pages  kswapd will scan is
> -represented by sc_age_cluster_min, which is done so that kswapd will also scan
> -small processes.
> -
> -The values  of  sc_pageout_weight  and sc_bufferout_weight are used to control
> -how many  tries  kswapd  will make in order to swap out one page/buffer. These
> -values can  be used to fine-tune the ratio between user pages and buffer/cache
> -memory. When  you find that your Linux system is swapping out too many process
> -pages in  order  to  satisfy  buffer  memory  demands,  you may want to either
> -increase sc_bufferout_weight, or decrease the value of sc_pageout_weight.
> +Please read Documentation/sysctl/vm.txt
>  
>  2.5 /proc/sys/dev - Device specific parameters
>  ----------------------------------------------
> @@ -1719,10 +1719,3 @@ need to  recompile  the kernel, or even 
>  command to write value into these files, thereby changing the default settings
>  of the kernel.
>  ------------------------------------------------------------------------------
> -
> -
> -
> -
> -
> -
> -

> --- a/Documentation/sysctl/vm.txt	2002-11-28 16:53:08.000000000 -0700
> +++ b/Documentation/sysctl/vm.txt	2003-11-12 17:35:11.000000000 -0700
> @@ -18,13 +18,10 @@
>  
>  Currently, these files are in /proc/sys/vm:
>  - bdflush
> -- buffermem
> -- freepages
>  - kswapd
>  - max_map_count
>  - overcommit_memory
>  - page-cluster
> -- pagecache
>  - pagetable_cache
>  
>  ==============================================================
> @@ -102,38 +99,6 @@
>  of buffer cache that is dirty which will stop bdflush.
>  The default is 20%, the miniumum is 0%, and the maxiumum is 100%.
>  ==============================================================
> -buffermem:
> -
> -The three values in this file correspond to the values in
> -the struct buffer_mem. It controls how much memory should
> -be used for buffer memory. The percentage is calculated
> -as a percentage of total system memory.
> -
> -The values are:
> -min_percent	-- this is the minimum percentage of memory
> -		   that should be spent on buffer memory
> -borrow_percent  -- UNUSED
> -max_percent     -- UNUSED
> -
> -==============================================================
> -freepages:
> -
> -This file contains the values in the struct freepages. That
> -struct contains three members: min, low and high.
> -
> -The meaning of the numbers is:
> -
> -freepages.min	When the number of free pages in the system
> -		reaches this number, only the kernel can
> -		allocate more memory.
> -freepages.low	If the number of free pages gets below this
> -		point, the kernel starts swapping aggressively.
> -freepages.high	The kernel tries to keep up to this amount of
> -		memory free; if memory comes below this point,
> -		the kernel gently starts swapping in the hopes
> -		that it never has to do real aggressive swapping.
> -
> -==============================================================
>  
>  kswapd:
>  
> @@ -208,24 +173,6 @@
>  
>  ==============================================================
>  
> -pagecache:
> -
> -This file does exactly the same as buffermem, only this
> -file controls the struct page_cache, and thus controls
> -the amount of memory used for the page cache.
> -
> -In 2.2, the page cache is used for 3 main purposes:
> -- caching read() data from files
> -- caching mmap()ed data and executable files
> -- swap cache
> -
> -When your system is both deep in swap and high on cache,
> -it probably means that a lot of the swapped data is being
> -cached, making for more efficient swapping than possible
> -with the 2.0 kernel.
> -
> -==============================================================
> -
>  pagetable_cache:
>  
>  The kernel keeps a number of page tables in a per-processor
> --- a/Documentation/filesystems/proc.txt	2004-05-21 22:54:13.000000000 +0200
> +++ b/Documentation/filesystems/proc.txt	2004-05-23 00:08:09.000000000 +0200
> @@ -999,54 +999,6 @@ nfract_sync
>  nfract_stop_bdflush
>  -------------------
>  
> -buffermem
> ----------
> -
> -The three  values  in  this  file  control  how much memory should be used for
> -buffer memory.  The  percentage  is calculated as a percentage of total system
> -memory.
> -
> -The values are:
> -
> -min_percent
> ------------
> -
> -This is  the  minimum  percentage  of  memory  that  should be spent on buffer
> -memory.
> -
> -borrow_percent
> ---------------
> -
> -When Linux is short on memory, and the buffer cache uses more than it has been
> -allotted, the  memory  management  (MM)  subsystem will prune the buffer cache
> -more heavily than other memory to compensate.
> -
> -max_percent
> ------------
> -
> -This is the maximum amount of memory that can be used for buffer memory.
> -
> -freepages
> ----------
> -
> -This file contains three values: min, low and high:
> -
> -min
> ----
> -When the  number  of  free  pages  in the system reaches this number, only the
> -kernel can allocate more memory.
> -
> -low
> ----
> -If the number of free pages falls below this point, the kernel starts swapping
> -aggressively.
> -
> -high
> -----
> -The kernel  tries  to  keep  up to this amount of memory free; if memory falls
> -below this point, the kernel starts gently swapping in the hopes that it never
> -has to do really aggressive swapping.
> -
>  kswapd
>  ------
>  
> @@ -1073,16 +1025,6 @@ This is  the  minimum number of times ks
>  is called. Basically it's just there to make sure that kswapd frees some pages
>  even when it's being called with minimum priority.
>  
> -swap_cluster
> -------------
> -
> -This is probably the greatest influence on system performance.
> -
> -swap_cluster is  the  number  of  pages kswapd writes in one turn. You'll want
> -this value  to  be  large  so that kswapd does its I/O in large chunks and the
> -disk doesn't  have  to  seek  as  often, but you don't want it to be too large
> -since that would flood the request queue.
> -
>  overcommit_memory
>  -----------------
>  
> @@ -1097,15 +1039,6 @@ On the  other  hand,  enabling this feat
>  and thrash the system to death, so large and/or important servers will want to
>  set this value to 0.
>  
> -pagecache
> ----------
> -
> -This file  does exactly the same job as buffermem, only this file controls the
> -amount of memory allowed for memory mapping and generic caching of files.
> -
> -You don't  want  the  minimum level to be too low, otherwise your system might
> -thrash when memory is tight or fragmentation is high.
> -
>  pagetable_cache
>  ---------------
>  

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