Re: [PATCH v4 3/6] perf: Shrink the size of the recursion counter.

[Peter Zijlstra]

On Mon, Jul 01, 2024 at 02:56:43PM +0200, Sebastian Andrzej Siewior wrote:
> On 2024-07-01 14:31:37 [+0200], Peter Zijlstra wrote:
> > On Mon, Jun 24, 2024 at 05:15:16PM +0200, Sebastian Andrzej Siewior wrote:
> > > There are four recursion counter, one for each context. The type of the
> > > counter is `int' but the counter is used as `bool' since it is only
> > > incremented if zero.
> > > 
> > > Reduce the type of the recursion counter to an unsigned char, keep the
> > > increment/ decrement operation.
> > 
> > Does this actually matter? Aren't u8 memops encoded by longer
> > instructions etc..
> 
> The goal here isn't to reduce the opcodes but to add it to task_struct
> without making it larger by filling a hole.

Changelog failed to mention this crucial fact.