diff mbox series

asm-generic: flush icache only when vma->vm_flags has VM_EXEC set

Message ID tencent_13A0B6B4A3136E46CC448874232A9F956006@qq.com
State New
Headers
Series asm-generic: flush icache only when vma->vm_flags has VM_EXEC set |

Commit Message

Yangyu Chen Jan. 9, 2024, 2:45 p.m. UTC 
  For some ISAs like RISC-V, which may not support bus broadcast-based
icache flushing instructions, it's necessary to send IPIs to all of the
CPUs in the system to flush the icache. This process can be expensive for
these ISAs and introduce disturbances during performance profiling.
Limiting the icache flush to occur only when the vma->vm_flags has VM_EXEC
can help minimize the frequency of these operations.

Signed-off-by: Yangyu Chen <cyy@cyyself.name>
---
 include/asm-generic/cacheflush.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Comments

Arnd Bergmann Jan. 9, 2024, 4:43 p.m. UTC | #1 
On Tue, Jan 9, 2024, at 15:45, Yangyu Chen wrote:
> For some ISAs like RISC-V, which may not support bus broadcast-based
> icache flushing instructions, it's necessary to send IPIs to all of the
> CPUs in the system to flush the icache. This process can be expensive for
> these ISAs and introduce disturbances during performance profiling.
> Limiting the icache flush to occur only when the vma->vm_flags has VM_EXEC
> can help minimize the frequency of these operations.
>
> Signed-off-by: Yangyu Chen <cyy@cyyself.name>
> ---
>  include/asm-generic/cacheflush.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/include/asm-generic/cacheflush.h 
> b/include/asm-generic/cacheflush.h
> index 84ec53ccc450..729d51536575 100644
> --- a/include/asm-generic/cacheflush.h
> +++ b/include/asm-generic/cacheflush.h
> @@ -102,7 +102,8 @@ static inline void flush_cache_vunmap(unsigned long 
> start, unsigned long end)
>  	do { \
>  		instrument_copy_to_user((void __user *)dst, src, len); \
>  		memcpy(dst, src, len); \
> -		flush_icache_user_page(vma, page, vaddr, len); \
> +		if (vma->vm_flags & VM_EXEC) \
> +			flush_icache_user_page(vma, page, vaddr, len); \
>  	} while (0)
>  #endif

This is not my normal area of expertise, but I wonder if you can't
just do this the same way as alpha and openrisc by having the
condition in architecture specific code.

     Arnd
diff mbox series

Patch

diff --git a/include/asm-generic/cacheflush.h b/include/asm-generic/cacheflush.h
index 84ec53ccc450..729d51536575 100644
--- a/include/asm-generic/cacheflush.h
+++ b/include/asm-generic/cacheflush.h
@@ -102,7 +102,8 @@  static inline void flush_cache_vunmap(unsigned long start, unsigned long end)
 	do { \
 		instrument_copy_to_user((void __user *)dst, src, len); \
 		memcpy(dst, src, len); \
-		flush_icache_user_page(vma, page, vaddr, len); \
+		if (vma->vm_flags & VM_EXEC) \
+			flush_icache_user_page(vma, page, vaddr, len); \
 	} while (0)
 #endif