* [PATCH] ARM: avoid cache flushing in flush_dcache_page()
@ 2016-11-07 10:30 Rabin Vincent
2016-11-07 11:35 ` Catalin Marinas
0 siblings, 1 reply; 4+ messages in thread
From: Rabin Vincent @ 2016-11-07 10:30 UTC (permalink / raw)
To: linux-arm-kernel
From: Rabin Vincent <rabinv@axis.com>
When the data cache is PIPT or VIPT non-aliasing, and cache operations
are broadcast by the hardware, we can always postpone the flush in
flush_dcache_page(). A similar change was done for ARM64 in commit
b5b6c9e9149d ("arm64: Avoid cache flushing in flush_dcache_page()").
Signed-off-by: Rabin Vincent <rabinv@axis.com>
---
arch/arm/mm/flush.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/arch/arm/mm/flush.c b/arch/arm/mm/flush.c
index 3cced84..f1e6190 100644
--- a/arch/arm/mm/flush.c
+++ b/arch/arm/mm/flush.c
@@ -327,6 +327,12 @@ void flush_dcache_page(struct page *page)
if (page == ZERO_PAGE(0))
return;
+ if (!cache_ops_need_broadcast() && cache_is_vipt_nonaliasing()) {
+ if (test_bit(PG_dcache_clean, &page->flags))
+ clear_bit(PG_dcache_clean, &page->flags);
+ return;
+ }
+
mapping = page_mapping(page);
if (!cache_ops_need_broadcast() &&
--
2.1.4
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH] ARM: avoid cache flushing in flush_dcache_page()
2016-11-07 10:30 [PATCH] ARM: avoid cache flushing in flush_dcache_page() Rabin Vincent
@ 2016-11-07 11:35 ` Catalin Marinas
2016-11-07 11:48 ` Russell King - ARM Linux
0 siblings, 1 reply; 4+ messages in thread
From: Catalin Marinas @ 2016-11-07 11:35 UTC (permalink / raw)
To: linux-arm-kernel
On Mon, Nov 07, 2016 at 11:30:24AM +0100, Rabin Vincent wrote:
> diff --git a/arch/arm/mm/flush.c b/arch/arm/mm/flush.c
> index 3cced84..f1e6190 100644
> --- a/arch/arm/mm/flush.c
> +++ b/arch/arm/mm/flush.c
> @@ -327,6 +327,12 @@ void flush_dcache_page(struct page *page)
> if (page == ZERO_PAGE(0))
> return;
>
> + if (!cache_ops_need_broadcast() && cache_is_vipt_nonaliasing()) {
> + if (test_bit(PG_dcache_clean, &page->flags))
> + clear_bit(PG_dcache_clean, &page->flags);
> + return;
> + }
> +
> mapping = page_mapping(page);
>
> if (!cache_ops_need_broadcast() &&
I'm ok with the logic in this patch but is there a way to combine the
two 'if' blocks together, just to keep the function shorter?
--
Catalin
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH] ARM: avoid cache flushing in flush_dcache_page()
2016-11-07 11:35 ` Catalin Marinas
@ 2016-11-07 11:48 ` Russell King - ARM Linux
2016-11-07 12:00 ` Catalin Marinas
0 siblings, 1 reply; 4+ messages in thread
From: Russell King - ARM Linux @ 2016-11-07 11:48 UTC (permalink / raw)
To: linux-arm-kernel
On Mon, Nov 07, 2016 at 11:35:27AM +0000, Catalin Marinas wrote:
> On Mon, Nov 07, 2016 at 11:30:24AM +0100, Rabin Vincent wrote:
> > diff --git a/arch/arm/mm/flush.c b/arch/arm/mm/flush.c
> > index 3cced84..f1e6190 100644
> > --- a/arch/arm/mm/flush.c
> > +++ b/arch/arm/mm/flush.c
> > @@ -327,6 +327,12 @@ void flush_dcache_page(struct page *page)
> > if (page == ZERO_PAGE(0))
> > return;
> >
> > + if (!cache_ops_need_broadcast() && cache_is_vipt_nonaliasing()) {
> > + if (test_bit(PG_dcache_clean, &page->flags))
> > + clear_bit(PG_dcache_clean, &page->flags);
> > + return;
> > + }
> > +
> > mapping = page_mapping(page);
> >
> > if (!cache_ops_need_broadcast() &&
>
> I'm ok with the logic in this patch but is there a way to combine the
> two 'if' blocks together, just to keep the function shorter?
Probably not without reducing code readability, or moving
page_mapping() before this new if() block (which may introduce
extra code into the path.)
As this path gets used for filesystem read/write, it would be a
good idea to keep it as efficient as possible.
--
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH] ARM: avoid cache flushing in flush_dcache_page()
2016-11-07 11:48 ` Russell King - ARM Linux
@ 2016-11-07 12:00 ` Catalin Marinas
0 siblings, 0 replies; 4+ messages in thread
From: Catalin Marinas @ 2016-11-07 12:00 UTC (permalink / raw)
To: linux-arm-kernel
On Mon, Nov 07, 2016 at 11:48:45AM +0000, Russell King - ARM Linux wrote:
> On Mon, Nov 07, 2016 at 11:35:27AM +0000, Catalin Marinas wrote:
> > On Mon, Nov 07, 2016 at 11:30:24AM +0100, Rabin Vincent wrote:
> > > diff --git a/arch/arm/mm/flush.c b/arch/arm/mm/flush.c
> > > index 3cced84..f1e6190 100644
> > > --- a/arch/arm/mm/flush.c
> > > +++ b/arch/arm/mm/flush.c
> > > @@ -327,6 +327,12 @@ void flush_dcache_page(struct page *page)
> > > if (page == ZERO_PAGE(0))
> > > return;
> > >
> > > + if (!cache_ops_need_broadcast() && cache_is_vipt_nonaliasing()) {
> > > + if (test_bit(PG_dcache_clean, &page->flags))
> > > + clear_bit(PG_dcache_clean, &page->flags);
> > > + return;
> > > + }
> > > +
> > > mapping = page_mapping(page);
> > >
> > > if (!cache_ops_need_broadcast() &&
> >
> > I'm ok with the logic in this patch but is there a way to combine the
> > two 'if' blocks together, just to keep the function shorter?
>
> Probably not without reducing code readability, or moving
> page_mapping() before this new if() block (which may introduce
> extra code into the path.)
You are right, we would need 'mapping' in the subsequent checks, so I
don't think the code would be more readable if we are to keep it
efficient. In this case:
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2016-11-07 12:00 UTC | newest]
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2016-11-07 10:30 [PATCH] ARM: avoid cache flushing in flush_dcache_page() Rabin Vincent
2016-11-07 11:35 ` Catalin Marinas
2016-11-07 11:48 ` Russell King - ARM Linux
2016-11-07 12:00 ` Catalin Marinas
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