From: SeongJae Park <sj@kernel.org>
To: Levi Yun <ppbuk5246@gmail.com>
Cc: sj@kernel.org, akpm@linux-foundation.org, damon@lists.linux.dev,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] damon: Use pmdp_get instead of drect dereferencing pmd.
Date: Thu, 27 Jul 2023 19:54:53 +0000 [thread overview]
Message-ID: <20230727195453.67611-1-sj@kernel.org> (raw)
In-Reply-To: <20230727183745.682880-1-ppbuk5246@gmail.com>
Hi Levi,
Thank you for this patch.
Nit for the subject, what about s/drect/directly/? Also, let's remove the
period at the end.
On Fri, 28 Jul 2023 03:37:45 +0900 Levi Yun <ppbuk5246@gmail.com> wrote:
> As ptep_get, Use the pmdp_get wrapper when we accessing pmdval
> instead of direct dereferencing pmd.
Nit: s/Use/use/ and s/direct/directly
>
> Signed-off-by: Levi Yun <ppbuk5246@gmail.com>
> ---
> mm/damon/ops-common.c | 2 +-
> mm/damon/paddr.c | 2 +-
> mm/damon/vaddr.c | 22 ++++++++++++++--------
> 3 files changed, 16 insertions(+), 10 deletions(-)
>
> diff --git a/mm/damon/ops-common.c b/mm/damon/ops-common.c
> index e940802a15a4..ac1c3fa80f98 100644
> --- a/mm/damon/ops-common.c
> +++ b/mm/damon/ops-common.c
> @@ -54,7 +54,7 @@ void damon_ptep_mkold(pte_t *pte, struct vm_area_struct *vma, unsigned long addr
> void damon_pmdp_mkold(pmd_t *pmd, struct vm_area_struct *vma, unsigned long addr)
> {
> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> - struct folio *folio = damon_get_folio(pmd_pfn(*pmd));
> + struct folio *folio = damon_get_folio(pmd_pfn(pmdp_get(pmd)));
>
> if (!folio)
> return;
> diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c
> index 40801e38fcf0..909db25efb35 100644
> --- a/mm/damon/paddr.c
> +++ b/mm/damon/paddr.c
> @@ -94,7 +94,7 @@ static bool __damon_pa_young(struct folio *folio, struct vm_area_struct *vma,
> mmu_notifier_test_young(vma->vm_mm, addr);
> } else {
> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> - *accessed = pmd_young(*pvmw.pmd) ||
> + *accessed = pmd_young(pmdp_get(pvmw.pmd)) ||
> !folio_test_idle(folio) ||
> mmu_notifier_test_young(vma->vm_mm, addr);
> #else
> diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c
> index 2fcc9731528a..82f7865719fe 100644
> --- a/mm/damon/vaddr.c
> +++ b/mm/damon/vaddr.c
> @@ -301,16 +301,19 @@ static int damon_mkold_pmd_entry(pmd_t *pmd, unsigned long addr,
> unsigned long next, struct mm_walk *walk)
> {
> pte_t *pte;
> + pmd_t pmde;
> spinlock_t *ptl;
>
> - if (pmd_trans_huge(*pmd)) {
> + if (pmd_trans_huge(pmdp_get_lockless(pmd))) {
I don't think we really need to use pmdp_get_lockless() here, since we will do
this check again with the lock, and we have the fallback for the intermediate
changes.
> ptl = pmd_lock(walk->mm, pmd);
> - if (!pmd_present(*pmd)) {
> + pmde = pmdp_get(pmd);
> +
> + if (!pmd_present(pmde)) {
> spin_unlock(ptl);
> return 0;
> }
>
> - if (pmd_trans_huge(*pmd)) {
> + if (pmd_trans_huge(pmde)) {
> damon_pmdp_mkold(pmd, walk->vma, addr);
> spin_unlock(ptl);
> return 0;
> @@ -434,26 +437,29 @@ static int damon_young_pmd_entry(pmd_t *pmd, unsigned long addr,
> {
> pte_t *pte;
> pte_t ptent;
> + pmd_t pmde;
This would cause below build warning if CONFIG_TRANSPARENT_HUGEPAGE is not
defined.
.../mm/damon/vaddr.c:440:8: warning: unused variable 'pmde' [-Wunused-variable]
440 | pmd_t pmde;
| ^~~~
> spinlock_t *ptl;
> struct folio *folio;
> struct damon_young_walk_private *priv = walk->private;
>
> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> - if (pmd_trans_huge(*pmd)) {
> + if (pmd_trans_huge(pmdp_get_lockless(pmd))) {
Again, pmdp_get() might be enough?
> ptl = pmd_lock(walk->mm, pmd);
> - if (!pmd_present(*pmd)) {
> + pmde = pmdp_get(pmd);
> +
> + if (!pmd_present(pmde)) {
> spin_unlock(ptl);
> return 0;
> }
>
> - if (!pmd_trans_huge(*pmd)) {
> + if (!pmd_trans_huge(pmde)) {
> spin_unlock(ptl);
> goto regular_page;
> }
> - folio = damon_get_folio(pmd_pfn(*pmd));
> + folio = damon_get_folio(pmd_pfn(pmde));
> if (!folio)
> goto huge_out;
> - if (pmd_young(*pmd) || !folio_test_idle(folio) ||
> + if (pmd_young(pmde) || !folio_test_idle(folio) ||
> mmu_notifier_test_young(walk->mm,
> addr))
> priv->young = true;
> --
> 2.37.2
>
Thanks,
SJ
next prev parent reply other threads:[~2023-07-27 19:55 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-27 18:37 Levi Yun
2023-07-27 19:54 ` SeongJae Park [this message]
2023-07-27 21:15 ` Yun Levi
2023-07-28 8:08 ` kernel test robot
2023-07-28 8:18 ` Yun Levi
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