[PATCH 0/2] proc.5 modification

[PATCH 0/2] proc.5 modification

[Elie De Brauwer]

Hello Michael,

Two patches related to proc.5:
 - the first patch adds an explanation of /proc/sys/vm/compact_memory
 - the second patch fixes two typo's (of which I'm guilty myself) in the 
   buddyinfo section of proc.5

my 2 cents
E.

Elie De Brauwer (2):
  proc.5: Explain /proc/sys/vm/compact_memory
  proc.5: tfix

 man5/proc.5 | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

-- 
2.1.4

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[PATCH 1/2] proc.5: Explain /proc/sys/vm/compact_memory

[Elie De Brauwer]

Since 2.6.36 [1] CONFIG_COMPACTION is supported in Linux (for a
detailed explanation see [2]). But in essence the contents of /proc/buddyinfo
shows how much contiguous areas of a certain size are available. These
numbers are not actually up to date as the Linux kernel will implicitely
trigger compaction (+- defragmentation) when an allocation is done.
This makes it difficult since you can't predict upfront whether or not a
large allocation will succeed or not.
By using /proc/sys/vm/compact_memory you can explicitely trigger compaction
to occur and /proc/buddyinfo will give a more realistic view on the
available memory in contiguous areas.

This patch updates proc.5 to explain the usage of this file and is
inspired upon Documentation/systcl/vm.txt [3]

[1] http://kernelnewbies.org/Linux_2_6_35#head-9cb0a1275559d40296da42efb7977896ac9edab7
[2] http://lwn.net/Articles/368869/
[3] http://lxr.free-electrons.com/source/Documentation/sysctl/vm.txt#L100

Signed-off-by: Elie De Brauwer <eliedebrauwer-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
---
 man5/proc.5 | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/man5/proc.5 b/man5/proc.5
index 860eb66..5bff2a0 100644
--- a/man5/proc.5
+++ b/man5/proc.5
@@ -3943,6 +3943,15 @@ On some systems, it is not present.
 This directory contains files for memory management tuning, buffer and
 cache management.
 .TP
+.IR /proc/sys/vm/compact_memory " (since Linux 2.6.35)"
+When 1 is written to this file, all zones are compacted such that free
+memory is available in contiguous blocks where possible.
+The effect of this action can be seen by examining
+.IR /proc/buddyinfo .
+.IP
+Only present if the kernel was configured with
+.BR CONFIG_COMPACTION .
+.TP
 .IR /proc/sys/vm/drop_caches " (since Linux 2.6.16)"
 Writing to this file causes the kernel to drop clean caches, dentries, and
 inodes from memory, causing that memory to become free.
-- 
2.1.4

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[PATCH 2/2] proc.5: tfix

[Elie De Brauwer]

Signed-off-by: Elie De Brauwer <eliedebrauwer-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
---
 man5/proc.5 | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/man5/proc.5 b/man5/proc.5
index 5bff2a0..9138ead 100644
--- a/man5/proc.5
+++ b/man5/proc.5
@@ -1981,12 +1981,12 @@ Node 0, zone  Normal   216   55  189  101   84   38   37   27    5    3  587
 
 In this example, there is one node containing three zones and there
 are 11 different chunk sizes.
-If the page size is 4 kilobyteis, then the first zone called
+If the page size is 4 kilobytes, then the first zone called
 .I DMA
 (on x86 the first 16 megabyte of memory) has 1 chunk of 4 kilobytes
 (order 0) available and has 3 chunks of 4 megabytes (order 10) available.
 
-If the memory is heavily fragmentated, the counters for higher
+If the memory is heavily fragmented, the counters for higher
 order chunks will be zero and allocation of large contiguous areas
 will fail.
 
-- 
2.1.4

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Re: [PATCH 1/2] proc.5: Explain /proc/sys/vm/compact_memory

[Michael Kerrisk (man-pages)]

On 01/22/2015 08:21 PM, Elie De Brauwer wrote:
> Since 2.6.36 [1] CONFIG_COMPACTION is supported in Linux (for a
> detailed explanation see [2]). But in essence the contents of /proc/buddyinfo
> shows how much contiguous areas of a certain size are available. These
> numbers are not actually up to date as the Linux kernel will implicitely
> trigger compaction (+- defragmentation) when an allocation is done.
> This makes it difficult since you can't predict upfront whether or not a
> large allocation will succeed or not.
> By using /proc/sys/vm/compact_memory you can explicitely trigger compaction
> to occur and /proc/buddyinfo will give a more realistic view on the
> available memory in contiguous areas.
> 
> This patch updates proc.5 to explain the usage of this file and is
> inspired upon Documentation/systcl/vm.txt [3]
> 
> [1] http://kernelnewbies.org/Linux_2_6_35#head-9cb0a1275559d40296da42efb7977896ac9edab7
> [2] http://lwn.net/Articles/368869/
> [3] http://lxr.free-electrons.com/source/Documentation/sysctl/vm.txt#L100

Thanks, Elie. Applied.

Cheers,

Michael


> Signed-off-by: Elie De Brauwer <eliedebrauwer-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> ---
>  man5/proc.5 | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/man5/proc.5 b/man5/proc.5
> index 860eb66..5bff2a0 100644
> --- a/man5/proc.5
> +++ b/man5/proc.5
> @@ -3943,6 +3943,15 @@ On some systems, it is not present.
>  This directory contains files for memory management tuning, buffer and
>  cache management.
>  .TP
> +.IR /proc/sys/vm/compact_memory " (since Linux 2.6.35)"
> +When 1 is written to this file, all zones are compacted such that free
> +memory is available in contiguous blocks where possible.
> +The effect of this action can be seen by examining
> +.IR /proc/buddyinfo .
> +.IP
> +Only present if the kernel was configured with
> +.BR CONFIG_COMPACTION .
> +.TP
>  .IR /proc/sys/vm/drop_caches " (since Linux 2.6.16)"
>  Writing to this file causes the kernel to drop clean caches, dentries, and
>  inodes from memory, causing that memory to become free.
> 


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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Re: [PATCH 2/2] proc.5: tfix

[Michael Kerrisk (man-pages)]

Thanks Elie!

Applied.

Cheers,

Michael


On 01/22/2015 08:21 PM, Elie De Brauwer wrote:
> Signed-off-by: Elie De Brauwer <eliedebrauwer-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> ---
>  man5/proc.5 | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/man5/proc.5 b/man5/proc.5
> index 5bff2a0..9138ead 100644
> --- a/man5/proc.5
> +++ b/man5/proc.5
> @@ -1981,12 +1981,12 @@ Node 0, zone  Normal   216   55  189  101   84   38   37   27    5    3  587
>  
>  In this example, there is one node containing three zones and there
>  are 11 different chunk sizes.
> -If the page size is 4 kilobyteis, then the first zone called
> +If the page size is 4 kilobytes, then the first zone called
>  .I DMA
>  (on x86 the first 16 megabyte of memory) has 1 chunk of 4 kilobytes
>  (order 0) available and has 3 chunks of 4 megabytes (order 10) available.
>  
> -If the memory is heavily fragmentated, the counters for higher
> +If the memory is heavily fragmented, the counters for higher
>  order chunks will be zero and allocation of large contiguous areas
>  will fail.
>  
> 


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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