Re: [BUG] msr-trace.h:42 suspicious rcu_dereference_check() usage!

From: Paul E. McKenney
Date: Tue Nov 22 2016 - 03:19:32 EST


On Mon, Nov 21, 2016 at 12:44:45PM -0800, Andi Kleen wrote:
> > > http://halobates.de/tracepoint-trace
> >
> > There's a lot of push and pop regs due to function calling. There's
> > places that inlines can still improve things, and perhaps even some
> > likely unlikelys well placed.
>
> Assuming you avoid all the push/pop and all the call/ret this would only be
> ~25% of the total instructions. There is just far too much logic and
> computation in there.
>
> % awk ' { print $5 } ' tracepoint-trace | sort | uniq -c | sort -rn
> 222 mov
> 57 push
> 57 pop
> 35 test
> 34 cmp
> 32 and
> 28 jz
> 25 jnz
> 21 ret
> 20 call
> 16 lea
> 11 add

Hmmm... It does indeed look like some performance analysis would be good...

Thanx, Paul