2023-10-06 06:03:20

by Mark-PK Tsai

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

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 <[email protected]>
---
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

2023-10-06 11:12:08

by Sergey Senozhatsky

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

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 <[email protected]>

TIL

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

Reviewed-by: Sergey Senozhatsky <[email protected]>


> 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().

2023-10-07 07:46:17

by Mark-PK Tsai

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

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 <[email protected]>
>
> 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 <[email protected]>
>
>
> > 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/[email protected]/