Messages in this thread Patch in this message | | | Date | Thu, 26 Nov 2015 23:05:32 +0800 | From | zhong jiang <> | Subject | Re: [PATCH] arm64: calculate the various pages number to show |
| |
On 2015/11/25 23:04, Mark Rutland wrote: > On Wed, Nov 25, 2015 at 09:41:12PM +0800, zhongjiang wrote: >> This patch add the interface to show the number of 4KB or 64KB page, >> aims to statistics the number of different types of pages. > > What is this useful for? Why do we want it? > > What does it account for, just the swapper? >
The patch is wirtten when I was in backport set_memory_ro. It can be used to detect whether there is a large page spliting and merging. large page will significantly reduce the TLB miss, and improve the system performance.
>> Signed-off-by: zhongjiang <zhongjiang@huawei.com> >> --- >> arch/arm64/include/asm/pgtable-types.h | 24 ++++++++++++++++++++++++ >> arch/arm64/mm/mmu.c | 28 ++++++++++++++++++++++++++++ >> arch/arm64/mm/pageattr.c | 31 +++++++++++++++++++++++++++++++ >> 3 files changed, 83 insertions(+), 0 deletions(-) >> >> diff --git a/arch/arm64/include/asm/pgtable-types.h b/arch/arm64/include/asm/pgtable-types.h >> index 2b1bd7e..aa52546 100644 >> --- a/arch/arm64/include/asm/pgtable-types.h >> +++ b/arch/arm64/include/asm/pgtable-types.h >> @@ -86,6 +86,30 @@ typedef pteval_t pgprot_t; >> >> #endif /* STRICT_MM_TYPECHECKS */ >> >> +struct seq_file; >> +extern void arch_report_meminfo(struct seq_file *m); >> + >> +enum pg_level { >> + PG_LEVEL_NONE, >> +#ifdef CONFIG_ARM64_4K_PAGES >> + PG_LEVEL_4K, >> + PG_LEVEL_2M, >> + PG_LEVEL_1G, >> +#else >> + PG_LEVEL_64K, >> + PG_LEVEL_512M, >> +#endif >> + PG_LEVEL_NUM >> +}; > > This doesn't account for 16K pages, and it means each call site has to > handle the various page sizes directly. > > It would be better to simply count PTE/PMD/PUD/PGD, then handle the size > conversion at the end when logging. >
yes, now I only consider the 4kb and 64kb. if the patch is approved ,I will improve it. each call site need two different varialbes to statistics, aiming to distinguish diffent pages. I think it will no more simple.
>> @@ -85,6 +86,11 @@ void split_pmd(pmd_t *pmd, pte_t *pte) >> set_pte(pte, pfn_pte(pfn, prot)); >> pfn++; >> } while (pte++, i++, i < PTRS_PER_PTE); >> +#ifdef CONFIG_ARM64_4K_PAGES >> + split_page_count(PG_LEVEL_2M); >> +#else >> + split_page_count(PG_LEVEL_512M); >> +#endif >> } > > e.g. here you'd just count PG_LEVEL_PMD, which would work regardless of > page size. > >> diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c >> index 7a5ff11..c1888b9 100644 >> --- a/arch/arm64/mm/pageattr.c >> +++ b/arch/arm64/mm/pageattr.c >> @@ -15,12 +15,43 @@ >> #include <linux/module.h> >> #include <linux/sched.h> >> >> +#include <linux/seq_file.h> >> #include <asm/pgalloc.h> >> #include <asm/pgtable.h> >> #include <asm/tlbflush.h> >> >> #include "mm.h" >> >> +static unsigned long direct_pages_count[PG_LEVEL_NUM]; > > This doesn't match reality by the time we start executing the kernel, > given we created page tables in head.S. > >> + >> +void update_page_count(int level, unsigned long pages) >> +{ >> + direct_pages_count[level] += pages; >> +} >> + >> +void split_page_count(int level) >> +{ >> + direct_pages_count[level]--; >> + direct_pages_count[level-1] += PTRS_PER_PTE; >> +} >> + >> +void arch_report_meminfo(struct seq_file *m) >> +{ >> +#ifdef CONFIG_ARM64_4K_PAGES >> + seq_printf(m, "DirectMap4k: %8lu kB\n", >> + direct_pages_count[PG_LEVEL_4K] << 2); >> + seq_printf(m, "DirectMap2M: %8lu kB\n", >> + direct_pages_count[PG_LEVEL_2M] << 11); >> + seq_printf(m, "DirectMap1G: %8lu kB\n", >> + direct_pages_count[PG_LEVEL_1G] << 20); >> +#else >> + seq_printf(m, "DirectMap64k: %8lu kB\n", >> + direct_pages_count[PG_LEVEL_64K] << 6); >> + seq_printf(m, "DirectMap512M: %8lu kB\n", >> + direct_pages_count[PG_LEVEL_512M] << 19); >> +#endif >> +} > > You could dynamuically determine the sizes here for each field, and not > have to have #ifdefs.>
I don't understand what you mean. I think it can be more readable and operability.
Thanks zhongjiang
> That all said, I don't see what this is useful for, and it looks very > fragile. > > Thanks, > Mark. > > . >
| |