Re: [PATCH] Performance Stats: Kernel patch

Andrew Morton wrote:

On Tue, 08 May 2007 16:26:51 +0000
Maxim Uvarov [off-list ref] wrote:

 

quoted

From: Maxim Uvarov <redacted>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: pavel@ucw.cz
Cc: linuxppc-dev@ozlabs.org
Cc: wli@holomorphy.com
Cc: dada1@cosmosbay.com
Cc: pavel@ucw.cz
   

Strange that linux-ppc was the only mailing list you copied?

 

Very strange. Possible stgit mail have limitation of CC.

quoted

Subject: [PATCH] Performance Stats: Kernel patch
Date: Tue, 08 May 2007 16:26:51 +0000
User-Agent: StGIT/0.12.1


Patch makes available to the user the following
task and process performance statistics:
* Involuntary Context Switches (task_struct->nivcsw)
* Voluntary Context Switches (task_struct->nvcsw)
* Number of system calls (added new counter
  thread_info->sysall_count)
           
Statistics information is available from:
       1. taskstats interface (Documentation/accounting/)
2. /proc/PID/status (task only).

This data is useful for detecting hyperactivity
patterns between processes.
   

syscall entry is a super-hotpath and there will be a developer revolt
if we go adding an incl to that path, sorry.

 

Yes, I know that it is very critical part of code. May be protection with
ifdef CONFIG_TASKSTATS  in all entry.S can be solution?
In that case we can be sure that nothing wrong can not happen,
and if this functionality is needed we can turn on this.

(Did that incl also cover the int 80 entry?)
 

Actually not. But counter increments each time when syscall  calls.
But it is in very save place, just after
        SAVE_ALL
        GET_THREAD_INFO(%ebp)
So it is very hard to break something.

(I'm going to update patch.)