Re: [PATCH] zsmalloc: use copy_page for full page copy

[Mark-PK Tsai (蔡沛剛)]

On Fri, 2023-10-06 at 20:11 +0900, Sergey Senozhatsky wrote:
>  	 
> External email : Please do not click links or open attachments until
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>  
> On (23/10/06 14:02), Mark-PK Tsai wrote:
> > Some architectures have implemented optimized
> > copy_page for full page copying, such as arm.
> > 
> > On my arm platform, use the copy_page helper
> > for single page copying is about 10 percent faster
> > than memcpy.
> > 
> > Signed-off-by: Mark-PK Tsai <mark-pk.tsai@xxxxxxxxxxxx>
> 
> TIL
> 
> I've never heard of arm's copy_page() before. Is it really much
> faster than memcpy()?

Based on my earlier tests, it seems better than memcpy
for full page copying.
The test code is just measures the copying time with
irq disabled.

> 
> Reviewed-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
> 
> 
> > diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> > index c743ce7a5f49..b1c0dad7f4cf 100644
> > --- a/mm/zsmalloc.c
> > +++ b/mm/zsmalloc.c
> > @@ -1839,7 +1839,7 @@ static int zs_page_migrate(struct page
> *newpage, struct page *page,
> >   * Here, any user cannot access all objects in the zspage so let's
> move.
> >   */
> >  d_addr = kmap_atomic(newpage);
> > -memcpy(d_addr, s_addr, PAGE_SIZE);
> > +copy_page(d_addr, s_addr);
> 
> I guess you can also look into patching zram_drv.c, which seem to
> have
> at least one PAGE_SIZE memcpy().

Thank. I've just post another patch for zram_drv.c as below link.


https://lore.kernel.org/lkml/20231007070554.8657-1-mark-pk.tsai@xxxxxxxxxxxx/