[Bug tapsets/15390] New: Add meminfo tapset

[Bug tapsets/15390] New: Add meminfo tapset

[Sergey.Klyaus@Tune-IT.Ru]

http://sourceware.org/bugzilla/show_bug.cgi?id=15390

             Bug #: 15390
           Summary: Add meminfo tapset
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: tapsets
        AssignedTo: systemtap@sourceware.org
        ReportedBy: Sergey.Klyaus@Tune-IT.Ru
    Classification: Unclassified


In Solaris/dtrace I can easily access `freemem of `availrmem variables which
providing information about current free or available memory. Linux also has
in-kernel interfaces, but I have to use Embedded C to access them. I propose
changes to memory.stp tapset which implements these functionality, i.e:

%{
    #include <linux/mmzone.h>
%}

function freemem:long() %{
    THIS->__retvalue = global_page_state(NR_FREE_PAGES);
%}

However, interface is quite unstable

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[Bug tapsets/15390] Add /proc/meminfo data to memory.stp tapset

[Sergey.Klyaus@Tune-IT.Ru]

http://sourceware.org/bugzilla/show_bug.cgi?id=15390

Sergey Klyaus <Sergey.Klyaus@Tune-IT.Ru> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|Add meminfo tapset          |Add /proc/meminfo data to
                   |                            |memory.stp tapset

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[Bug tapsets/15390] Add /proc/meminfo data to memory.stp tapset

[dsmith at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=15390

David Smith <dsmith at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |dsmith at redhat dot com

--- Comment #1 from David Smith <dsmith at redhat dot com> 2013-04-23 14:56:39 UTC ---
This is an interesting idea, that seems doable. You are right, the kernel
internal interface has changed somewhat over time (from looking at 2.6.9 source
vs. current source). For the example you included, I wonder if it wouldn't be
better to go ahead and call si_meminfo(), which would insulate us from kernel
changes a bit.

Which of the /proc/meminfo values would you consider most helpful for stap to
provide?

Another thought I had here was we could to name the stap functions after the
associated /proc/meminfo output, i.e. meminfo_memtotal(), meminfo_memfree(),
meminfo_buffers(), etc.

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