Re: [PATCH 4/4] scsi: sym53c8xx_2: replace __get_free_pages() with kmalloc()

[Hannes Reinecke]

On 6/30/26 12:54 PM, Mike Rapoport (Microsoft) wrote:
> sym53c8xx_2 driver has an internal memory allocator for small
> allocations of the driver structures. The backing memory for that
> allocator is allocated with __get_free_pages().
>
> This memory can be allocated with kmalloc() as there's nothing special
> about it to go directly to the page allocator.
>
> 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() and free_pages() with
> kfree().
>
> Link: https://lore.kernel.org/all/635405e4-9423-4a25-a6e7-e03c8ea0bcbe@xxxxxxxxxx
> Signed-off-by: Mike Rapoport (Microsoft) <rppt@xxxxxxxxxx>
> ---
>   drivers/scsi/sym53c8xx_2/sym_hipd.h | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/scsi/sym53c8xx_2/sym_hipd.h b/drivers/scsi/sym53c8xx_2/sym_hipd.h
> index 9231a2899064..aa365e8ba66f 100644
> --- a/drivers/scsi/sym53c8xx_2/sym_hipd.h
> +++ b/drivers/scsi/sym53c8xx_2/sym_hipd.h
> @@ -1110,9 +1110,9 @@ sym_build_sge(struct sym_hcb *np, struct sym_tblmove *data, u64 badd, int len)
>    */
>   
>   #define sym_get_mem_cluster()	\
> -	(void *) __get_free_pages(GFP_ATOMIC, SYM_MEM_PAGE_ORDER)
> +	kmalloc(PAGE_SIZE << SYM_MEM_PAGE_ORDER, GFP_ATOMIC)
>   #define sym_free_mem_cluster(p)	\
> -	free_pages((unsigned long)p, SYM_MEM_PAGE_ORDER)
> +	kfree(p)
>   
>   /*
>    *  Link between free memory chunks of a given size.
Reviewed-by: Hannes Reinecke <hare@xxxxxxxxxx>

Cheers,

Hannes
--
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@xxxxxxxx                               +49 911 74053 688
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