[PATCH] zsmalloc: use copy_page for full page copy

[PATCH] zsmalloc: use copy_page for full page copy

[Mark-PK Tsai]

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@mediatek.com>
---
 mm/zsmalloc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

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);
 	kunmap_atomic(d_addr);
 
 	for (addr = s_addr + offset; addr < s_addr + PAGE_SIZE;
-- 
2.18.0

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

[Sergey Senozhatsky]

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@mediatek.com>

TIL

I've never heard of arm's copy_page() before. Is it really much
faster than memcpy()?

Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>


> 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().

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
> you have verified the sender or the content.
>  
> 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@mediatek.com>
> 
> 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@chromium.org>
> 
> 
> > 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@mediatek.com/