On 05.03.2025 00:22, Andrew Cooper wrote:
> There are two issues. First, pi_test_and_clear_on() pulls the cache-line to
> the CPU and dirties it even if there's nothing outstanding, but the final
> bitmap_for_each() is O(256) when O(8) would do, and would avoid multiple
> atomic updates to the same IRR word.
>
> Rewrite it from scratch, explaining what's going on at each step.
>
> Bloat-o-meter reports 177 -> 145 (net -32), but real improvement is the
> removal of calls to __find_{first,next}_bit() hidden behind bitmap_for_each().
Nit: As said in reply to v2, there are no underscores on the two find
functions bitmap_for_each() uses.
> No functional change.
>
> Signed-off-by: Andrew Cooper <[email protected]>
> ---
> CC: Jan Beulich <[email protected]>
> CC: Roger Pau Monné <[email protected]>
>
> https://gitlab.com/xen-project/people/andyhhp/xen/-/pipelines/1699791518
>
> v3:
> * Fix IRR scatter address calculation
> * Spelling/Grammar improvements
The description starting with "There are two issues" I fear it still
doesn't become quite clear what the 2nd issue is. I can only assume it's
the use of bitmap_for_each() that now goes away.
Preferably with this tweaked a little further
Reviewed-by: Jan Beulich <[email protected]>
Jan
