Re: [PATCH v10 6/7] ARM: add pmd_[dirty|mkclean] for THP

From: Minchan Kim
Date: Mon Jul 07 2014 - 21:09:45 EST


On Mon, Jul 07, 2014 at 10:22:48AM +0100, Steve Capper wrote:
> On Mon, Jul 07, 2014 at 09:53:57AM +0900, Minchan Kim wrote:
> > MADV_FREE needs pmd_dirty and pmd_mkclean for detecting recent
> > overwrite of the contents since MADV_FREE syscall is called for
> > THP page.
> >
> > This patch adds pmd_dirty and pmd_mkclean for THP page MADV_FREE
> > support.
> >
> > Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> > Cc: Will Deacon <will.deacon@xxxxxxx>
> > Cc: Steve Capper <steve.capper@xxxxxxxxxx>
> > Cc: Russell King <linux@xxxxxxxxxxxxxxxx>
> > Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> > Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
> > ---
> > arch/arm64/include/asm/pgtable.h | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> > index 579702086488..f3ec01cef04f 100644
> > --- a/arch/arm64/include/asm/pgtable.h
> > +++ b/arch/arm64/include/asm/pgtable.h
> > @@ -240,10 +240,12 @@ static inline pmd_t pte_pmd(pte_t pte)
> > #endif
> >
> > #define pmd_young(pmd) pte_young(pmd_pte(pmd))
> > +#define pmd_dirty(pmd) pte_dirty(pmd_pte(pmd))
> > #define pmd_wrprotect(pmd) pte_pmd(pte_wrprotect(pmd_pte(pmd)))
> > #define pmd_mksplitting(pmd) pte_pmd(pte_mkspecial(pmd_pte(pmd)))
> > #define pmd_mkold(pmd) pte_pmd(pte_mkold(pmd_pte(pmd)))
> > #define pmd_mkwrite(pmd) pte_pmd(pte_mkwrite(pmd_pte(pmd)))
> > +#define pmd_mkclean(pmd) pte_pmd(pte_mkclean(pmd_pte(pmd)))
> > #define pmd_mkdirty(pmd) pte_pmd(pte_mkdirty(pmd_pte(pmd)))
> > #define pmd_mkyoung(pmd) pte_pmd(pte_mkyoung(pmd_pte(pmd)))
> > #define pmd_mknotpresent(pmd) (__pmd(pmd_val(pmd) & ~PMD_TYPE_MASK))
> > --
> > 2.0.0
> >
>
> Hi Minchan,

Hello Steve and Will,

>
> This looks good to me too.
> As Will said this applies to arm64, we will also need a version for:
> arch/arm/include/asm/pgtable-3level.h.

Does it work?

diff --git a/arch/arm/include/asm/pgtable-3level.h b/arch/arm/include/asm/pgtable-3level.h
index 85c60adc8b60..3a7bb8dc7d05 100644
--- a/arch/arm/include/asm/pgtable-3level.h
+++ b/arch/arm/include/asm/pgtable-3level.h
@@ -220,6 +220,8 @@ static inline pmd_t *pmd_offset(pud_t *pud, unsigned long addr)
#define pmd_trans_splitting(pmd) (pmd_val(pmd) & PMD_SECT_SPLITTING)
#endif

+#define pmd_dirty (pmd_val(pmd) & PMD_SECT_DIRTY)
+
#define PMD_BIT_FUNC(fn,op) \
static inline pmd_t pmd_##fn(pmd_t pmd) { pmd_val(pmd) op; return pmd; }

@@ -228,6 +230,7 @@ PMD_BIT_FUNC(mkold, &= ~PMD_SECT_AF);
PMD_BIT_FUNC(mksplitting, |= PMD_SECT_SPLITTING);
PMD_BIT_FUNC(mkwrite, &= ~PMD_SECT_RDONLY);
PMD_BIT_FUNC(mkdirty, |= PMD_SECT_DIRTY);
+PMD_BIT_FUNC(mkclean, &= ~PMD_SECT_DIRTY);
PMD_BIT_FUNC(mkyoung, |= PMD_SECT_AF);

#define pmd_mkhuge(pmd) (__pmd(pmd_val(pmd) & ~PMD_TABLE_BIT))
--
2.0.0

>
> Is there a testcase we can run to check that this patch set is working
> well for arm/arm64?

I just run several instance of attached simple stress with heavy kernel
build in parallel on 1G RAM machine.

Thanks for the review!

>
> Cheers,
> --
> Steve
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@xxxxxxxxxx For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>

--
Kind regards,
Minchan Kim
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <pthread.h>

#define CHUNK_SIZE (20<<20)
#define SLEEP_TIME_SEC 2
#define NUM_THREAD 12
#define QUIT 1000

int quit;

void alloc_thp()
{
int i;
int ret;
char *ptr;

/* should be aligned with 2M which is THP page size */
ret = posix_memalign((void**)&ptr, 2<<20, CHUNK_SIZE);
if (ret) {
fprintf(stderr, "fail to allocate\n");
return;
}

memset(ptr, 'a', CHUNK_SIZE);
ret = madvise(ptr, CHUNK_SIZE, 5);
if (ret) {
perror("fail to madvise");
return;
}

sleep(SLEEP_TIME_SEC);

memset(ptr, 'b', CHUNK_SIZE);
sleep(SLEEP_TIME_SEC);

for (i = 0; i < CHUNK_SIZE; i++) {
if (ptr[i] != 'b') {
fprintf(stderr, "fail to verify\n");
fprintf(stderr, "Something wrong\n");
return;
}
}

free(ptr);
}

void *thread_alloc(void *priv)
{
int n = 0;

while(!quit) {
alloc_thp();
if (!(n++ % 5))
printf("I'm working\n");
if (n == QUIT)
return;
}
}

int main()
{
int i, ret;
pthread_t thread[NUM_THREAD];

for (i = 0; i < NUM_THREAD; i++) {
ret = pthread_create(&thread[i], NULL, thread_alloc, NULL);
if (ret) {
perror("fail to create thread\n");
return 1;
}
}

scanf("%d", &quit);
for (i = 0; i < NUM_THREAD; i++)
pthread_join(thread[i], NULL);

printf("Test Done\n");
return 0;
}