Re: [PATCH v2 3/7] mm: introduce do_zap_pte_range()
From: Qi Zheng
Date: Wed Nov 13 2024 - 23:12:36 EST
On 2024/11/14 11:09, Qi Zheng wrote:
On 2024/11/13 19:43, David Hildenbrand wrote:
On 13.11.24 03:40, Qi Zheng wrote:
On 2024/11/13 01:00, David Hildenbrand wrote:
On 31.10.24 09:13, Qi Zheng wrote:
This commit introduces do_zap_pte_range() to actually zap the PTEs,
which
will help improve code readability and facilitate secondary
checking of
the processed PTEs in the future.
No functional change.
Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
---
mm/memory.c | 45 ++++++++++++++++++++++++++-------------------
1 file changed, 26 insertions(+), 19 deletions(-)
diff --git a/mm/memory.c b/mm/memory.c
index bd9ebe0f4471f..c1150e62dd073 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1657,6 +1657,27 @@ static inline int zap_nonpresent_ptes(struct
mmu_gather *tlb,
return nr;
}
+static inline int do_zap_pte_range(struct mmu_gather *tlb,
+ struct vm_area_struct *vma, pte_t *pte,
+ unsigned long addr, unsigned long end,
+ struct zap_details *details, int *rss,
+ bool *force_flush, bool *force_break)
+{
+ pte_t ptent = ptep_get(pte);
+ int max_nr = (end - addr) / PAGE_SIZE;
+
+ if (pte_none(ptent))
+ return 1;
Maybe we should just skip all applicable pte_none() here directly.
Do you mean we should keep pte_none() case in zap_pte_range()? Like
below:
No rather an addon patch that will simply skip over all
consecutive pte_none, like:
if (pte_none(ptent)) {
int nr;
for (nr = 1; nr < max_nr; nr++) {
ptent = ptep_get(pte + nr);
if (pte_none(ptent))
continue;
}
max_nr -= nr;
if (!max_nr)
return nr;
addr += nr * PAGE_SIZE;
pte += nr;
}
I tend to hand over the pte/addr increments here to the loop
outside do_zap_pte_range(), like this:
Finally, I choose to introduce skip_none_ptes() to do this:
diff --git a/mm/memory.c b/mm/memory.c
index bd9ebe0f4471f..24633d0e1445a 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1657,6 +1657,28 @@ static inline int zap_nonpresent_ptes(struct
mmu_gather *tlb,
return nr;
}
+static inline int skip_none_ptes(pte_t *pte, unsigned long addr,
+ unsigned long end)
+{
+ pte_t ptent = ptep_get(pte);
+ int max_nr;
+ int nr;
+
+ if (!pte_none(ptent))
+ return 0;
+
+ max_nr = (end - addr) / PAGE_SIZE;
+ nr = 1;
+
+ for (; nr < max_nr; nr++) {
+ ptent = ptep_get(pte + nr);
+ if (!pte_none(ptent))
+ break;
+ }
+
+ return nr;
+}
+
static unsigned long zap_pte_range(struct mmu_gather *tlb,
struct vm_area_struct *vma, pmd_t *pmd,
unsigned long addr, unsigned long end,
@@ -1682,13 +1704,17 @@ static unsigned long zap_pte_range(struct
mmu_gather *tlb,
pte_t ptent = ptep_get(pte);
int max_nr;
- nr = 1;
- if (pte_none(ptent))
- continue;
-
if (need_resched())
break;
+ nr = skip_none_ptes(pte, addr, end);
+ if (nr) {
+ addr += PAGE_SIZE * nr;
+ if (addr == end)
+ break;
+ pte += nr;
+ }
+
max_nr = (end - addr) / PAGE_SIZE;
if (pte_present(ptent)) {
nr = zap_present_ptes(tlb, vma, pte, ptent, max_nr,
Thanks!