LinuxLists.cc - [PATCH] Documentation: Describe the shared memory usage/accounting

2015-11-19 18:58:23

Subject: [PATCH] Documentation: Describe the shared memory usage/accounting

The Shared Memory accounting support is present in Kernel since
commit 4b02108ac1b3 ("mm: oom analysis: add shmem vmstat") and in userland
free(1) since 2014. This patch updates the Documentation to reflect
this change.

Signed-off-by: Rodrigo Freire <[email protected]>
---
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -842,6 +842,7 @@
Writeback: 0 kB
AnonPages: 861800 kB
Mapped: 280372 kB
+Shmem: 644 kB
Slab: 284364 kB
SReclaimable: 159856 kB
SUnreclaim: 124508 kB
@@ -898,6 +899,7 @@
AnonPages: Non-file backed pages mapped into userspace page tables
AnonHugePages: Non-file backed huge pages mapped into userspace page tables
Mapped: files which have been mmaped, such as libraries
+ Shmem: Total memory used by shared memory (shmem) and tmpfs
Slab: in-kernel data structures cache
SReclaimable: Part of Slab, that might be reclaimed, such as caches
SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure
--- a/Documentation/filesystems/tmpfs.txt
+++ b/Documentation/filesystems/tmpfs.txt
@@ -17,10 +17,10 @@
cannot swap and you do not have the possibility to resize them.

Since tmpfs lives completely in the page cache and on swap, all tmpfs
-pages currently in memory will show up as cached. It will not show up
-as shared or something like that. Further on you can check the actual
-RAM+swap use of a tmpfs instance with df(1) and du(1).
-
+pages will be shown in /proc/meminfo as "Shmem" and "Shared" in
+free(1). Notice that shared memory pages (see ipcs(1)) will be also
+counted as shared memory. The most reliable way to get the count is
+using df(1) and du(1).

tmpfs has the following uses:

---
1.7.1

2015-12-05 11:09:08

by Rodrigo Freire

[permalink] [raw]

Subject: [PATCH RESEND] Documentation: Describe the shared memory usage/accounting

2015-12-21 15:19:27

by Vlastimil Babka

[permalink] [raw]

Subject: Re: [PATCH] Documentation: Describe the shared memory usage/accounting

On 11/19/2015 07:58 PM, Rodrigo Freire wrote:
>
> The Shared Memory accounting support is present in Kernel since
> commit 4b02108ac1b3 ("mm: oom analysis: add shmem vmstat") and in userland
> free(1) since 2014. This patch updates the Documentation to reflect
> this change.
>
> Signed-off-by: Rodrigo Freire <[email protected]>

You should send to Andrew Morton and maybe CC Hugh Dickins at the very
least. Sending just to mailing list doesn't guarantee maintainers will
pick it up due to the high volume there.
Also note that your RESEND has broken whitespace.

> ---
> --- a/Documentation/filesystems/proc.txt
> +++ b/Documentation/filesystems/proc.txt
> @@ -842,6 +842,7 @@
> Writeback: 0 kB
> AnonPages: 861800 kB
> Mapped: 280372 kB
> +Shmem: 644 kB
> Slab: 284364 kB
> SReclaimable: 159856 kB
> SUnreclaim: 124508 kB
> @@ -898,6 +899,7 @@
> AnonPages: Non-file backed pages mapped into userspace page tables
> AnonHugePages: Non-file backed huge pages mapped into userspace page tables
> Mapped: files which have been mmaped, such as libraries
> + Shmem: Total memory used by shared memory (shmem) and tmpfs
> Slab: in-kernel data structures cache
> SReclaimable: Part of Slab, that might be reclaimed, such as caches
> SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure
> --- a/Documentation/filesystems/tmpfs.txt
> +++ b/Documentation/filesystems/tmpfs.txt
> @@ -17,10 +17,10 @@
> cannot swap and you do not have the possibility to resize them.
>
> Since tmpfs lives completely in the page cache and on swap, all tmpfs
> -pages currently in memory will show up as cached. It will not show up
> -as shared or something like that. Further on you can check the actual
> -RAM+swap use of a tmpfs instance with df(1) and du(1).
> -
> +pages will be shown in /proc/meminfo as "Shmem" and "Shared" in

It would be IMHO clearer if it said:
... will be shown as "Shmem" in /proc/meminfo and "Shared" in ...

> +free(1). Notice that shared memory pages (see ipcs(1)) will be also
> +counted as shared memory.

Too much of "shared memory" here. Maybe something like:
"However, these counters also include shared memory (shmem)."

> The most reliable way to get the count is
> +using df(1) and du(1).
>
> tmpfs has the following uses:
>
> ---
> 1.7.1
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to [email protected]. For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"[email protected]"> [email protected] </a>
>

2015-12-21 18:08:10

by Rodrigo Freire

[permalink] [raw]

Subject: [PATCH V2] Documentation: Describe the shared memory usage/accounting

The Shared Memory accounting support is present in Kernel since
commit 4b02108ac1b3 ("mm: oom analysis: add shmem vmstat") and in
userland free(1) since 2014. This patch updates the Documentation to
reflect this change.

Signed-off-by: Rodrigo Freire <[email protected]>
---
V2: Better wording as per Vlastimil Babka's suggestions
---
Documentation/filesystems/proc.txt | 2 ++
Documentation/filesystems/tmpfs.txt | 8 ++++----
2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index 402ab99..8ca61a0 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -842,6 +842,7 @@ Dirty: 968 kB
Writeback: 0 kB
AnonPages: 861800 kB
Mapped: 280372 kB
+Shmem: 644 kB
Slab: 284364 kB
SReclaimable: 159856 kB
SUnreclaim: 124508 kB
@@ -898,6 +899,7 @@ MemAvailable: An estimate of how much memory is available for starting new
AnonPages: Non-file backed pages mapped into userspace page tables
AnonHugePages: Non-file backed huge pages mapped into userspace page tables
Mapped: files which have been mmaped, such as libraries
+ Shmem: Total memory used by shared memory (shmem) and tmpfs
Slab: in-kernel data structures cache
SReclaimable: Part of Slab, that might be reclaimed, such as caches
SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure
diff --git a/Documentation/filesystems/tmpfs.txt b/Documentation/filesystems/tmpfs.txt
index 98ef551..d1abf2d 100644
--- a/Documentation/filesystems/tmpfs.txt
+++ b/Documentation/filesystems/tmpfs.txt
@@ -17,10 +17,10 @@ RAM, where you have to create an ordinary filesystem on top. Ramdisks
cannot swap and you do not have the possibility to resize them.

Since tmpfs lives completely in the page cache and on swap, all tmpfs
-pages currently in memory will show up as cached. It will not show up
-as shared or something like that. Further on you can check the actual
-RAM+swap use of a tmpfs instance with df(1) and du(1).
-
+pages will be shown as "Shmem" in /proc/meminfo and "Shared" in
+free(1). Notice that these counters also include shared memory
+(shmem, see ipcs(1)). The most reliable way to get the count is
+using df(1) and du(1).

tmpfs has the following uses:

--
1.7.1

2015-12-22 15:52:13

by Vlastimil Babka

[permalink] [raw]

Subject: Re: [PATCH V2] Documentation: Describe the shared memory usage/accounting

On 12/21/2015 07:07 PM, Rodrigo Freire wrote:
>
> The Shared Memory accounting support is present in Kernel since
> commit 4b02108ac1b3 ("mm: oom analysis: add shmem vmstat") and in
> userland free(1) since 2014. This patch updates the Documentation to
> reflect this change.
>
> Signed-off-by: Rodrigo Freire <[email protected]>

Acked-by: Vlastimil Babka <[email protected]>