On 10/03/2011 04:36 PM, Kirill A. Shutemov wrote:

On Mon, Oct 03, 2011 at 04:26:41PM +0400, Glauber Costa wrote:

quoted

On 10/03/2011 04:25 PM, Kirill A. Shutemov wrote:

quoted

On Mon, Oct 03, 2011 at 04:19:18PM +0400, Glauber Costa wrote:

quoted

On 10/03/2011 04:14 PM, Kirill A. Shutemov wrote:

quoted

On Mon, Oct 03, 2011 at 02:18:42PM +0400, Glauber Costa wrote:

quoted

This patch introduces kmem.tcp_current_memory file, living in the
kmem_cgroup filesystem. It is a simple read-only file that displays the
amount of kernel memory currently consumed by the cgroup.

Signed-off-by: Glauber Costa<redacted>
CC: David S. Miller<davem@davemloft.net>
CC: Hiroyouki Kamezawa<redacted>
CC: Eric W. Biederman<redacted>
---
    Documentation/cgroups/memory.txt |    1 +
    mm/memcontrol.c                  |   11 +++++++++++
    2 files changed, 12 insertions(+), 0 deletions(-)

diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt
index 1ffde3e..f5a539d 100644
--- a/Documentation/cgroups/memory.txt
+++ b/Documentation/cgroups/memory.txt

@@ -79,6 +79,7 @@ Brief summary of control files.
     memory.independent_kmem_limit	 # select whether or not kernel memory limits are
    				   independent of user limits
     memory.kmem.tcp.max_memory      # set/show hard limit for tcp buf memory
+ memory.kmem.tcp.current_memory  # show current tcp buf memory allocation

Both are in pages, right?
Shouldn't it be scaled to bytes and named uniform with other memcg file?
memory.kmem.tcp.limit_in_bytes/usage_in_bytes.

You are absolutely correct.
Since the internal tcp comparison works, I just ended up never noticing
this.

Should we have failcnt and max_usage_in_bytes for tcp as well?

Well, we get a fail count from the tracer anyway, so I don't really see
a need for that. I see value in having it for the slab allocation
itself, but since this only controls the memory pressure framework, I
think we can live without it.

That said, this is not a strong opinion. I can add it if you'd prefer.

It's good for userspace to have the same set of files for all domains:
  - memory;
  - memory.memsw;
  - memory.kmem;
  - memory.kmem.tcp;
  - etc.
Userspace can reuse code for handling them in this case.

Ok. Back on this.

Not all domains have all files anyway.

max_usage seems to be a property of the main memcg, not of its domains.
failcnt is present on memsw, and on that only. The problem here, is that 
this can fail ( and usually will ) in codepaths outside the memory
controller. (see net/core/sock.c:__sk_mem_schedule)

Also, max_usage makes sense for kernel memory as a whole, but I don't 
think it makes sense here as we're only controlling a specific pressure 
condition.

So in a nutshell: I'd like to leave this alone, and add 
kmem.max_usage_in_bytes and kmem.failcnt to the to soon-to-land-here 
slab accounting patches. (Where the actual allocation happens)

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