* [PATCH] util/cacheflush: Avoid flushing dcache twice when not necessary
@ 2023-06-05 19:59 Philippe Mathieu-Daudé
2023-06-05 20:00 ` Philippe Mathieu-Daudé
` (2 more replies)
0 siblings, 3 replies; 5+ messages in thread
From: Philippe Mathieu-Daudé @ 2023-06-05 19:59 UTC (permalink / raw)
To: qemu-devel
Cc: Paolo Bonzini, Richard Henderson, Akihiko Odaki,
Philippe Mathieu-Daudé
<libkern/OSCacheControl.h> describes sys_icache_invalidate() as
"equivalent to sys_cache_control(kCacheFunctionPrepareForExecution)",
having kCacheFunctionPrepareForExecution defined as:
/* Prepare memory for execution. This should be called
* after writing machine instructions to memory, before
* executing them. It syncs the dcache and icache. [...]
*/
Since the dcache is also sync'd, we can avoid the sys_dcache_flush()
call when both rx/rw pointers are equal.
Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
Based-on: <20230605175647.88395-2-philmd@linaro.org>
---
util/cacheflush.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/util/cacheflush.c b/util/cacheflush.c
index de35616718..a08906155a 100644
--- a/util/cacheflush.c
+++ b/util/cacheflush.c
@@ -241,7 +241,14 @@ static void __attribute__((constructor)) init_cache_info(void)
void flush_idcache_range(uintptr_t rx, uintptr_t rw, size_t len)
{
- sys_dcache_flush((void *)rw, len);
+ if (rx == rw) {
+ /*
+ * sys_icache_invalidate() syncs the dcache and icache,
+ * so no need to call sys_dcache_flush().
+ */
+ } else {
+ sys_dcache_flush((void *)rw, len);
+ }
sys_icache_invalidate((void *)rx, len);
}
#else
--
2.38.1
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] util/cacheflush: Avoid flushing dcache twice when not necessary
2023-06-05 19:59 [PATCH] util/cacheflush: Avoid flushing dcache twice when not necessary Philippe Mathieu-Daudé
@ 2023-06-05 20:00 ` Philippe Mathieu-Daudé
2023-06-05 20:03 ` Richard Henderson
2023-06-05 21:56 ` BALATON Zoltan
2 siblings, 0 replies; 5+ messages in thread
From: Philippe Mathieu-Daudé @ 2023-06-05 20:00 UTC (permalink / raw)
To: qemu-devel; +Cc: Paolo Bonzini, Richard Henderson, Akihiko Odaki
Subject: "Avoid flushing dcache twice [on Darwin] when not necessary"
On 5/6/23 21:59, Philippe Mathieu-Daudé wrote:
> <libkern/OSCacheControl.h> describes sys_icache_invalidate() as
> "equivalent to sys_cache_control(kCacheFunctionPrepareForExecution)",
> having kCacheFunctionPrepareForExecution defined as:
>
> /* Prepare memory for execution. This should be called
> * after writing machine instructions to memory, before
> * executing them. It syncs the dcache and icache. [...]
> */
>
> Since the dcache is also sync'd, we can avoid the sys_dcache_flush()
> call when both rx/rw pointers are equal.
>
> Suggested-by: Richard Henderson <richard.henderson@linaro.org>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
> Based-on: <20230605175647.88395-2-philmd@linaro.org>
> ---
> util/cacheflush.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/util/cacheflush.c b/util/cacheflush.c
> index de35616718..a08906155a 100644
> --- a/util/cacheflush.c
> +++ b/util/cacheflush.c
> @@ -241,7 +241,14 @@ static void __attribute__((constructor)) init_cache_info(void)
>
> void flush_idcache_range(uintptr_t rx, uintptr_t rw, size_t len)
> {
> - sys_dcache_flush((void *)rw, len);
> + if (rx == rw) {
> + /*
> + * sys_icache_invalidate() syncs the dcache and icache,
> + * so no need to call sys_dcache_flush().
> + */
> + } else {
> + sys_dcache_flush((void *)rw, len);
> + }
> sys_icache_invalidate((void *)rx, len);
> }
> #else
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] util/cacheflush: Avoid flushing dcache twice when not necessary
2023-06-05 19:59 [PATCH] util/cacheflush: Avoid flushing dcache twice when not necessary Philippe Mathieu-Daudé
2023-06-05 20:00 ` Philippe Mathieu-Daudé
@ 2023-06-05 20:03 ` Richard Henderson
2023-06-05 21:56 ` BALATON Zoltan
2 siblings, 0 replies; 5+ messages in thread
From: Richard Henderson @ 2023-06-05 20:03 UTC (permalink / raw)
To: Philippe Mathieu-Daudé, qemu-devel; +Cc: Paolo Bonzini, Akihiko Odaki
On 6/5/23 12:59, Philippe Mathieu-Daudé wrote:
> <libkern/OSCacheControl.h> describes sys_icache_invalidate() as
> "equivalent to sys_cache_control(kCacheFunctionPrepareForExecution)",
> having kCacheFunctionPrepareForExecution defined as:
>
> /* Prepare memory for execution. This should be called
> * after writing machine instructions to memory, before
> * executing them. It syncs the dcache and icache. [...]
> */
>
> Since the dcache is also sync'd, we can avoid the sys_dcache_flush()
> call when both rx/rw pointers are equal.
>
> Suggested-by: Richard Henderson<richard.henderson@linaro.org>
> Signed-off-by: Philippe Mathieu-Daudé<philmd@linaro.org>
> ---
> Based-on:<20230605175647.88395-2-philmd@linaro.org>
> ---
> util/cacheflush.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
r~
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] util/cacheflush: Avoid flushing dcache twice when not necessary
2023-06-05 19:59 [PATCH] util/cacheflush: Avoid flushing dcache twice when not necessary Philippe Mathieu-Daudé
2023-06-05 20:00 ` Philippe Mathieu-Daudé
2023-06-05 20:03 ` Richard Henderson
@ 2023-06-05 21:56 ` BALATON Zoltan
2023-06-05 22:33 ` Philippe Mathieu-Daudé
2 siblings, 1 reply; 5+ messages in thread
From: BALATON Zoltan @ 2023-06-05 21:56 UTC (permalink / raw)
To: Philippe Mathieu-Daudé
Cc: qemu-devel, Paolo Bonzini, Richard Henderson, Akihiko Odaki
[-- Attachment #1: Type: text/plain, Size: 1676 bytes --]
On Mon, 5 Jun 2023, Philippe Mathieu-Daudé wrote:
> <libkern/OSCacheControl.h> describes sys_icache_invalidate() as
> "equivalent to sys_cache_control(kCacheFunctionPrepareForExecution)",
> having kCacheFunctionPrepareForExecution defined as:
>
> /* Prepare memory for execution. This should be called
> * after writing machine instructions to memory, before
> * executing them. It syncs the dcache and icache. [...]
> */
>
> Since the dcache is also sync'd, we can avoid the sys_dcache_flush()
> call when both rx/rw pointers are equal.
>
> Suggested-by: Richard Henderson <richard.henderson@linaro.org>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
> Based-on: <20230605175647.88395-2-philmd@linaro.org>
> ---
> util/cacheflush.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/util/cacheflush.c b/util/cacheflush.c
> index de35616718..a08906155a 100644
> --- a/util/cacheflush.c
> +++ b/util/cacheflush.c
> @@ -241,7 +241,14 @@ static void __attribute__((constructor)) init_cache_info(void)
>
> void flush_idcache_range(uintptr_t rx, uintptr_t rw, size_t len)
> {
> - sys_dcache_flush((void *)rw, len);
> + if (rx == rw) {
Isn't it more straight forward to use rx != rw and drop the else branch
than having an empty if branch? You can still keep the comment above the
if to explain it if needed.
Regards,
BALATON Zoltan
> + /*
> + * sys_icache_invalidate() syncs the dcache and icache,
> + * so no need to call sys_dcache_flush().
> + */
> + } else {
> + sys_dcache_flush((void *)rw, len);
> + }
> sys_icache_invalidate((void *)rx, len);
> }
> #else
>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] util/cacheflush: Avoid flushing dcache twice when not necessary
2023-06-05 21:56 ` BALATON Zoltan
@ 2023-06-05 22:33 ` Philippe Mathieu-Daudé
0 siblings, 0 replies; 5+ messages in thread
From: Philippe Mathieu-Daudé @ 2023-06-05 22:33 UTC (permalink / raw)
To: BALATON Zoltan
Cc: qemu-devel, Paolo Bonzini, Richard Henderson, Akihiko Odaki
On 5/6/23 23:56, BALATON Zoltan wrote:
> On Mon, 5 Jun 2023, Philippe Mathieu-Daudé wrote:
>> <libkern/OSCacheControl.h> describes sys_icache_invalidate() as
>> "equivalent to sys_cache_control(kCacheFunctionPrepareForExecution)",
>> having kCacheFunctionPrepareForExecution defined as:
>>
>> /* Prepare memory for execution. This should be called
>> * after writing machine instructions to memory, before
>> * executing them. It syncs the dcache and icache. [...]
>> */
>>
>> Since the dcache is also sync'd, we can avoid the sys_dcache_flush()
>> call when both rx/rw pointers are equal.
>>
>> Suggested-by: Richard Henderson <richard.henderson@linaro.org>
>> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
>> ---
>> Based-on: <20230605175647.88395-2-philmd@linaro.org>
>> ---
>> util/cacheflush.c | 9 ++++++++-
>> 1 file changed, 8 insertions(+), 1 deletion(-)
>>
>> diff --git a/util/cacheflush.c b/util/cacheflush.c
>> index de35616718..a08906155a 100644
>> --- a/util/cacheflush.c
>> +++ b/util/cacheflush.c
>> @@ -241,7 +241,14 @@ static void __attribute__((constructor))
>> init_cache_info(void)
>>
>> void flush_idcache_range(uintptr_t rx, uintptr_t rw, size_t len)
>> {
>> - sys_dcache_flush((void *)rw, len);
>> + if (rx == rw) {
>
> Isn't it more straight forward to use rx != rw and drop the else branch
> than having an empty if branch? You can still keep the comment above the
> if to explain it if needed.
I tried that first but found it was not obvious, so chose this
form because it seemed clearer to me.
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2023-06-05 22:33 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2023-06-05 19:59 [PATCH] util/cacheflush: Avoid flushing dcache twice when not necessary Philippe Mathieu-Daudé
2023-06-05 20:00 ` Philippe Mathieu-Daudé
2023-06-05 20:03 ` Richard Henderson
2023-06-05 21:56 ` BALATON Zoltan
2023-06-05 22:33 ` Philippe Mathieu-Daudé
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.