Alexander Shishkin <alexander.shish...@linux.intel.com> writes: > Currently, the AUX buffer allocator will use high-order allocations > for PMUs that don't support hardware scatter-gather chaining to ensure > large contiguous blocks of pages, and always use an array of single > pages otherwise. > > There is, however, a tangible performance benefit in using larger chunks > of contiguous memory even in the latter case, that comes from not having > to fetch the next page's address at every page boundary. In particular, > a task running under Intel PT on an Atom CPU shows 1.5%-2% less runtime > penalty with a single multi-page output region in snapshot mode (no PMI) > than with multiple single-page output regions, from ~6% down to ~4%. For > the snapshot mode it does make a difference as it is intended to run over > long periods of time. > > For this reason, change the allocation policy to always optimistically > start with the highest possible order when allocating pages for the AUX > buffer, desceding until the allocation succeeds or order zero allocation > fails. > > Signed-off-by: Alexander Shishkin <alexander.shish...@linux.intel.com>
Does anybody want to pick this up? Thanks, -- Alex
