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@bytedance.com>
---
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;
+
+ if (pte_present(ptent))
+ return zap_present_ptes(tlb, vma, pte, ptent, max_nr,
+ addr, details, rss, force_flush,
+ force_break);
+
+ return zap_nonpresent_ptes(tlb, vma, pte, ptent, max_nr, addr,
+ details, rss);
+}
+
static unsigned long zap_pte_range(struct mmu_gather *tlb,
struct vm_area_struct *vma, pmd_t *pmd,
unsigned long addr, unsigned long end,
@@ -1679,28 +1700,14 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
flush_tlb_batched_pending(mm);
arch_enter_lazy_mmu_mode();
do {
- pte_t ptent = ptep_get(pte);
- int max_nr;
-
- nr = 1;
- if (pte_none(ptent))
- continue;
-
if (need_resched())
break;
- max_nr = (end - addr) / PAGE_SIZE;
- if (pte_present(ptent)) {
- nr = zap_present_ptes(tlb, vma, pte, ptent, max_nr,
- addr, details, rss, &force_flush,
- &force_break);
- if (unlikely(force_break)) {
- addr += nr * PAGE_SIZE;
- break;
- }
- } else {
- nr = zap_nonpresent_ptes(tlb, vma, pte, ptent, max_nr,
- addr, details, rss);
+ nr = do_zap_pte_range(tlb, vma, pte, addr, end, details, rss,
+ &force_flush, &force_break);
+ if (unlikely(force_break)) {
+ addr += nr * PAGE_SIZE;
+ break;
}
} while (pte += nr, addr += PAGE_SIZE * nr, addr != end);
--
2.20.1On 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@bytedance.com>
> ---
> 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.
Acked-by: David Hildenbrand <david@redhat.com>
--
Cheers,
David / dhildenb
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@bytedance.com>
>> ---
>> 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:
diff --git a/mm/memory.c b/mm/memory.c
index 002aa4f454fa0..2ccdcf37b7a46 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1666,9 +1666,6 @@ static inline int do_zap_pte_range(struct
mmu_gather *tlb,
pte_t ptent = ptep_get(pte);
int max_nr = (end - addr) / PAGE_SIZE;
- if (pte_none(ptent))
- return 1;
-
if (pte_present(ptent))
return zap_present_ptes(tlb, vma, pte, ptent, max_nr,
addr, details, rss, force_flush,
@@ -1704,11 +1701,15 @@ static unsigned long zap_pte_range(struct
mmu_gather *tlb,
if (need_resched())
break;
- nr = do_zap_pte_range(tlb, vma, pte, addr, end, details,
rss,
- &force_flush, &force_break);
- if (unlikely(force_break)) {
- addr += nr * PAGE_SIZE;
- break;
+ if (pte_none(ptep_get(pte))) {
+ nr = 1;
+ } else {
+ nr = do_zap_pte_range(tlb, vma, pte, addr, end,
details,
+ rss, &force_flush,
&force_break);
+ if (unlikely(force_break)) {
+ addr += nr * PAGE_SIZE;
+ break;
+ }
}
} while (pte += nr, addr += PAGE_SIZE * nr, addr != end);
This avoids repeated checks for pte_none() later. Both are fine for
me, will change to this in the next version.
>
> Acked-by: David Hildenbrand <david@redhat.com>
Thanks!
>
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@bytedance.com>
>>> ---
>>> 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;
}
Assuming that it's likely more common to have larger pte_none() holes
that single ones, optimizing out the
need_resched()+force_break+incremental pte/addr increments etc.
--
Cheers,
David / dhildenb
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@bytedance.com>
>>>> ---
>>>> 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:
diff --git a/mm/memory.c b/mm/memory.c
index bd9ebe0f4471f..2367a1c19edd6 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1657,6 +1657,36 @@ 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)) {
+ int nr = 1;
+
+ for (; nr < max_nr; nr++) {
+ ptent = ptep_get(pte + nr);
+ if (!pte_none(ptent))
+ break;
+ }
+
+ return nr;
+ }
+
+ if (pte_present(ptent))
+ return zap_present_ptes(tlb, vma, pte, ptent, max_nr,
+ addr, details, rss, force_flush,
+ force_break);
+
+ return zap_nonpresent_ptes(tlb, vma, pte, ptent, max_nr, addr,
+ details, rss);
+}
+
static unsigned long zap_pte_range(struct mmu_gather *tlb,
struct vm_area_struct *vma, pmd_t *pmd,
unsigned long addr, unsigned long end,
@@ -1679,28 +1709,14 @@ static unsigned long zap_pte_range(struct
mmu_gather *tlb,
flush_tlb_batched_pending(mm);
arch_enter_lazy_mmu_mode();
do {
- pte_t ptent = ptep_get(pte);
- int max_nr;
-
- nr = 1;
- if (pte_none(ptent))
- continue;
-
if (need_resched())
break;
- max_nr = (end - addr) / PAGE_SIZE;
- if (pte_present(ptent)) {
- nr = zap_present_ptes(tlb, vma, pte, ptent, max_nr,
- addr, details, rss,
&force_flush,
- &force_break);
- if (unlikely(force_break)) {
- addr += nr * PAGE_SIZE;
- break;
- }
- } else {
- nr = zap_nonpresent_ptes(tlb, vma, pte, ptent,
max_nr,
- addr, details, rss);
+ nr = do_zap_pte_range(tlb, vma, pte, addr, end, details,
+ rss, &force_flush, &force_break);
+ if (unlikely(force_break)) {
+ addr += nr * PAGE_SIZE;
+ break;
}
} while (pte += nr, addr += PAGE_SIZE * nr, addr != end);
>
> Assuming that it's likely more common to have larger pte_none() holes
> that single ones, optimizing out the
> need_resched()+force_break+incremental pte/addr increments etc.
>
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@bytedance.com>
>>>>> ---
>>>>> 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!
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@bytedance.com>
>>>> ---
>>>> 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;
> }
>
> Assuming that it's likely more common to have larger pte_none() holes
> that single ones, optimizing out the
> need_resched()+force_break+incremental pte/addr increments etc.
Ah, got it. And I agree with you, will change to it in the next version.
Thanks!
>
On Thu, Oct 31, 2024 at 9:14 AM Qi Zheng <zhengqi.arch@bytedance.com> 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@bytedance.com> Reviewed-by: Jann Horn <jannh@google.com>
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