Re: [PATCH V3 4/7] x86/entry: move PUSH_AND_CLEAR_REGS out of error_entry

[Lai Jiangshan]

On Wed, Mar 16, 2022 at 11:07 PM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:

>
> So I don't much care about the orc data, that's only used when
> unwinding, a relatively rare occasion, anyway. But the text increase
> does bother me a little, this can blow up I$ misses on syscall heavy
> workloads.

It has nothing to do with the syscall.

It does add a lot in I$.  But it is fortunate that the footprint
is the same (before and after the patch) for a single exception vector.
For example heavy #PF workloads.

Footprint will increase after this patch when two or more exception
vectors happen heavily at the same time, for example when #PF and
timer are occurring heavily.

We can put PUSH_AND_CLEAR_REGS in a single function to reduce the
footprint for heavy multi-exception workloads.  What do you think?