[lkml]   [2004]   [Sep]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [profile] amortize atomic hit count increments
William Lee Irwin III <> wrote:
> read_proc_profile()
> does not flush the per-cpu hashtables because flushing may cause
> timeslice overrun on the systems where prof_buffer cacheline bounces
> are so problematic as to livelock the timer interrupt.

That's a bit of a problem, isn't it? As we can accumulate an arbitrarily
large number of hits within the hash table is it not possible that the
/proc/profile results could be grossly inaccurate?

If you had two front-ends per cpu to the profiling buffer then the CPU
which is running the /proc/profile read could tell all the other CPUs to
flip to their alternate buffer and can then perform accumulation at its

How does oprofile get around this? I guess in most modes the CPUs are not

One wonders how long we should keep flogging the /prof/profile profiling
code. What systems are seeing this livelock?
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2005-03-22 14:06    [W:0.144 / U:16.340 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site