| Subject | Re: [RFC PATCH 3/4] kvm: Add guest side support for free memory hints | From | Dave Hansen <> | Date | Mon, 4 Feb 2019 11:44:29 -0800 |
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On 2/4/19 10:15 AM, Alexander Duyck wrote: > +#ifdef CONFIG_KVM_GUEST > +#include <linux/jump_label.h> > +extern struct static_key_false pv_free_page_hint_enabled; > + > +#define HAVE_ARCH_FREE_PAGE > +void __arch_free_page(struct page *page, unsigned int order); > +static inline void arch_free_page(struct page *page, unsigned int order) > +{ > + if (static_branch_unlikely(&pv_free_page_hint_enabled)) > + __arch_free_page(page, order); > +} > +#endif
So, this ends up with at least a call, a branch and a ret added to the order-0 paths, including freeing pages to the per-cpu-pageset lists. That seems worrisome.
What performance testing has been performed to look into the overhead added to those paths?
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