2021-11-18 08:19:52

by Zhaoyang Huang

Subject: [RFC PATCH] arch: arm64: try to use PTE_CONT when change page attr

From: Zhaoyang Huang <[email protected]>

kernel will use the min granularity when rodata_full enabled which
make TLB pressure high. Furthermore, there is no PTE_CONT applied.
Try to improve these a little by apply PTE_CONT when change page's
attr.

Signed-off-by: Zhaoyang Huang <[email protected]>
---
arch/arm64/mm/pageattr.c | 62 ++++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 58 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
index a3bacd7..0b6a354 100644
--- a/arch/arm64/mm/pageattr.c
+++ b/arch/arm64/mm/pageattr.c
@@ -61,8 +61,13 @@ static int change_memory_common(unsigned long addr, int numpages,
unsigned long start = addr;
unsigned long size = PAGE_SIZE * numpages;
unsigned long end = start + size;
+ unsigned long cont_pte_start = 0;
+ unsigned long cont_pte_end = 0;
+ unsigned long cont_pmd_start = 0;
+ unsigned long cont_pmd_end = 0;
+ pgprot_t orig_set_mask = set_mask;
struct vm_struct *area;
- int i;
+ int i = 0;

if (!PAGE_ALIGNED(addr)) {
start &= PAGE_MASK;
@@ -98,9 +103,58 @@ static int change_memory_common(unsigned long addr, int numpages,
*/
if (rodata_full && (pgprot_val(set_mask) == PTE_RDONLY ||
pgprot_val(clear_mask) == PTE_RDONLY)) {
- for (i = 0; i < area->nr_pages; i++) {
- __change_memory_common((u64)page_address(area->pages[i]),
- PAGE_SIZE, set_mask, clear_mask);
+ cont_pmd_start = (start + ~CONT_PMD_MASK + 1) & CONT_PMD_MASK;
+ cont_pmd_end = cont_pmd_start + ~CONT_PMD_MASK + 1;
+ cont_pte_start = (start + ~CONT_PTE_MASK + 1) & CONT_PTE_MASK;
+ cont_pte_end = cont_pte_start + ~CONT_PTE_MASK + 1;
+
+ if (addr <= cont_pmd_start && end > cont_pmd_end) {
+ do {
+ __change_memory_common((u64)page_address(area->pages[i]),
+ PAGE_SIZE, set_mask, clear_mask);
+ i++;
+ addr++;
+ } while(addr < cont_pmd_start);
+ do {
+ set_mask = __pgprot(pgprot_val(set_mask) | PTE_CONT);
+ __change_memory_common((u64)page_address(area->pages[i]),
+ PAGE_SIZE, set_mask, clear_mask);
+ i++;
+ addr++;
+ } while(addr < cont_pmd_end);
+ set_mask = orig_set_mask;
+ do {
+ __change_memory_common((u64)page_address(area->pages[i]),
+ PAGE_SIZE, set_mask, clear_mask);
+ i++;
+ addr++;
+ } while(addr <= end);
+ } else if (addr <= cont_pte_start && end > cont_pte_end) {
+ do {
+ __change_memory_common((u64)page_address(area->pages[i]),
+ PAGE_SIZE, set_mask, clear_mask);
+ i++;
+ addr++;
+ } while(addr < cont_pte_start);
+ do {
+ set_mask = __pgprot(pgprot_val(set_mask) | PTE_CONT);
+ __change_memory_common((u64)page_address(area->pages[i]),
+ PAGE_SIZE, set_mask, clear_mask);
+ i++;
+ addr++;
+ } while(addr < cont_pte_end);
+ set_mask = orig_set_mask;
+ do {
+ __change_memory_common((u64)page_address(area->pages[i]),
+ PAGE_SIZE, set_mask, clear_mask);
+ i++;
+ addr++;
+ } while(addr <= end);
+ } else {
+ for (i = 0; i < area->nr_pages; i++) {
+ __change_memory_common((u64)page_address(area->pages[i]),
+ PAGE_SIZE, set_mask, clear_mask);
+ }
}
}

--
1.9.1

2021-11-18 11:44:51

by Zhaoyang Huang

Subject: Re: [RFC PATCH] arch: arm64: try to use PTE_CONT when change page attr

forget the criteria for judging the linear address range, so please
ignore this patch

On Thu, Nov 18, 2021 at 4:18 PM Huangzhaoyang <[email protected]> wrote:
>
> From: Zhaoyang Huang <[email protected]>
>
> kernel will use the min granularity when rodata_full enabled which
> make TLB pressure high. Furthermore, there is no PTE_CONT applied.
> Try to improve these a little by apply PTE_CONT when change page's
> attr.
>
> Signed-off-by: Zhaoyang Huang <[email protected]>
> ---
> arch/arm64/mm/pageattr.c | 62 ++++++++++++++++++++++++++++++++++++++++++++----
> 1 file changed, 58 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
> index a3bacd7..0b6a354 100644
> --- a/arch/arm64/mm/pageattr.c
> +++ b/arch/arm64/mm/pageattr.c
> @@ -61,8 +61,13 @@ static int change_memory_common(unsigned long addr, int numpages,
> unsigned long start = addr;
> unsigned long size = PAGE_SIZE * numpages;
> unsigned long end = start + size;
> + unsigned long cont_pte_start = 0;
> + unsigned long cont_pte_end = 0;
> + unsigned long cont_pmd_start = 0;
> + unsigned long cont_pmd_end = 0;
> + pgprot_t orig_set_mask = set_mask;
> struct vm_struct *area;
> - int i;
> + int i = 0;
>
> if (!PAGE_ALIGNED(addr)) {
> start &= PAGE_MASK;
> @@ -98,9 +103,58 @@ static int change_memory_common(unsigned long addr, int numpages,
> */
> if (rodata_full && (pgprot_val(set_mask) == PTE_RDONLY ||
> pgprot_val(clear_mask) == PTE_RDONLY)) {
> - for (i = 0; i < area->nr_pages; i++) {
> - __change_memory_common((u64)page_address(area->pages[i]),
> - PAGE_SIZE, set_mask, clear_mask);
> + cont_pmd_start = (start + ~CONT_PMD_MASK + 1) & CONT_PMD_MASK;
> + cont_pmd_end = cont_pmd_start + ~CONT_PMD_MASK + 1;
> + cont_pte_start = (start + ~CONT_PTE_MASK + 1) & CONT_PTE_MASK;
> + cont_pte_end = cont_pte_start + ~CONT_PTE_MASK + 1;
> +
> + if (addr <= cont_pmd_start && end > cont_pmd_end) {
> + do {
> + __change_memory_common((u64)page_address(area->pages[i]),
> + PAGE_SIZE, set_mask, clear_mask);
> + i++;
> + addr++;
> + } while(addr < cont_pmd_start);
> + do {
> + set_mask = __pgprot(pgprot_val(set_mask) | PTE_CONT);
> + __change_memory_common((u64)page_address(area->pages[i]),
> + PAGE_SIZE, set_mask, clear_mask);
> + i++;
> + addr++;
> + } while(addr < cont_pmd_end);
> + set_mask = orig_set_mask;
> + do {
> + __change_memory_common((u64)page_address(area->pages[i]),
> + PAGE_SIZE, set_mask, clear_mask);
> + i++;
> + addr++;
> + } while(addr <= end);
> + } else if (addr <= cont_pte_start && end > cont_pte_end) {
> + do {
> + __change_memory_common((u64)page_address(area->pages[i]),
> + PAGE_SIZE, set_mask, clear_mask);
> + i++;
> + addr++;
> + } while(addr < cont_pte_start);
> + do {
> + set_mask = __pgprot(pgprot_val(set_mask) | PTE_CONT);
> + __change_memory_common((u64)page_address(area->pages[i]),
> + PAGE_SIZE, set_mask, clear_mask);
> + i++;
> + addr++;
> + } while(addr < cont_pte_end);
> + set_mask = orig_set_mask;
> + do {
> + __change_memory_common((u64)page_address(area->pages[i]),
> + PAGE_SIZE, set_mask, clear_mask);
> + i++;
> + addr++;
> + } while(addr <= end);
> + } else {
> + for (i = 0; i < area->nr_pages; i++) {
> + __change_memory_common((u64)page_address(area->pages[i]),
> + PAGE_SIZE, set_mask, clear_mask);
> + }
> }
> }
>
> --
> 1.9.1
>