ARM: avoid cache flushing in flush_dcache_page()
PATCH 1/1 ARM: avoid cache flushing in flush_dcache_page()
From: Rabin Vincent <[email protected]>
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()").
--- arch/arm/mm/flush.c | 6 ++++++ 1 file changed, 6 insertions(+)
arch/arm/mm/flush.c +6 -0
@@ -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() &&
Signature · 1 line
2.1.4
PATCH 1/1 ARM: avoid cache flushing in flush_dcache_page()
Quoted 7 lines · Rabin Vincent
arch/arm/mm/flush.c +0
-0@@ -327,6 +327,12 @@ void flush_dcache_page(struct page *page)if (page ==ZERO_PAGE (0 ))return ;
arch/arm/mm/flush.c void flush_dcache_page(struct page *page) · line 338
Quoted 10 lines
arch/arm/mm/flush.c +6
-0+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?
Signature · 1 line
Catalin
Russell King - ARM Linux
maintainerPATCH 1/1 ARM: avoid cache flushing in flush_dcache_page()
Quoted 17 lines · Catalin Marinas
Quoted 16 lines · Rabin Vincent
arch/arm/mm/flush.c +6
-0@@ -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);
Quoted 4 lines
arch/arm/mm/flush.c void flush_dcache_page(struct page *page) · line 338
Quoted 1 line
arch/arm/mm/flush.c +0
-0if (!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.
Signature · 3 lines
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.
PATCH 1/1 ARM: avoid cache flushing in flush_dcache_page()
Quoted 18 lines · Russell King - ARM Linux
Quoted 17 lines · Catalin Marinas
Quoted 16 lines · Rabin Vincent
arch/arm/mm/flush.c +6
-0@@ -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);
Quoted 8 lines
Quoted 4 lines
arch/arm/mm/flush.c void flush_dcache_page(struct page *page) · line 338
Quoted 1 line
arch/arm/mm/flush.c +0
-0if (!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 newif()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: