Re: [PATCH v2] xen/events: replace page allocator calls with k[mz]alloc()

["Jürgen Groß" <jgross@suse.com>]

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On 10.11.26 08:14, Mike Rapoport (Microsoft) wrote:
> set_evtchn_to_irq() allocates a page for the event channel to IRQ
> number software lookup table and xen_init_IRQ() allocates the PIRQ EOI
> bitmap that is registered with the hypervisor in PV domains.
> 
> These buffers can be allocated with kmalloc() as there's nothing special
> about them to go directly to the page allocator. The PIRQ EOI bitmap is
> passed to the hypervisor by its frame number and must occupy a whole
> page, which is guaranteed for a PAGE_SIZE kmalloc() allocation as it is
> naturally aligned.
> 
> kmalloc() provides a better API that does not require ugly casts and
> kfree() does not need to know the size of the freed object.
> 
> Performance difference between kmalloc() and __get_free_pages() is not
> measurable as both allocators take an object/page from a per-CPU list for
> fast path allocations.
> 
> For the slow path the performance is anyway determined by the amount of
> reclaim involved rather than by what allocator is used.
> 
> Replace use of __get_free_pages() with kmalloc(), __get_free_page() with
> __GFP_ZERO with kzalloc() and free_page[s]() with kfree().
> 
> Link: https://lore.kernel.org/all/635405e4-9423-4a25-a6e7-e03c8ea0bcbe@redhat.com
> Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Juergen Gross <jgross@suse.com>


Juergen

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