On 26.10.20 18:33, Vlastimil Babka wrote:
prep_new_page() will always zero a new page (regardless of __GFP_ZERO) when init_on_alloc is enabled, but will also always skip zeroing if the page was already zeroed on free by init_on_free or page poisoning. The latter check implemented by free_pages_prezeroed() can involve two different static keys. As prep_new_page() is really a hot path, let's introduce a single static key free_pages_not_prezeroed for this purpose and initialize it in init_mem_debugging().
Is this actually observable in practice? This smells like micro-optimization to me.
Also, I thought the whole reason for static keys is to have basically no overhead at runtime, so I wonder if replacing two static key checks by a single one actually makes *some* difference.
-- Thanks, David / dhildenb
