* [PATCH] powerpc/32s: Don't flush all TLBs when flushing one page
@ 2020-01-31 15:37 Christophe Leroy
2020-01-31 15:51 ` Segher Boessenkool
0 siblings, 1 reply; 8+ messages in thread
From: Christophe Leroy @ 2020-01-31 15:37 UTC (permalink / raw)
To: Benjamin Herrenschmidt, Paul Mackerras, Michael Ellerman
Cc: linux-kernel, linuxppc-dev
When flushing a range, the flushing function flushes all TLBs.
When the range is a single page, do a page flush instead.
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
arch/powerpc/mm/book3s32/tlb.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/mm/book3s32/tlb.c b/arch/powerpc/mm/book3s32/tlb.c
index 2fcd321040ff..8e0089065a7e 100644
--- a/arch/powerpc/mm/book3s32/tlb.c
+++ b/arch/powerpc/mm/book3s32/tlb.c
@@ -79,14 +79,17 @@ static void flush_range(struct mm_struct *mm, unsigned long start,
int count;
unsigned int ctx = mm->context.id;
+ start &= PAGE_MASK;
+ end = (end - 1) | ~PAGE_MASK;
if (!Hash) {
- _tlbia();
+ if (end - start == PAGE_SIZE)
+ _tlbie(start);
+ else
+ _tlbia();
return;
}
- start &= PAGE_MASK;
if (start >= end)
return;
- end = (end - 1) | ~PAGE_MASK;
pmd = pmd_offset(pud_offset(pgd_offset(mm, start), start), start);
for (;;) {
pmd_end = ((start + PGDIR_SIZE) & PGDIR_MASK) - 1;
--
2.25.0
^ permalink raw reply related [flat|nested] 8+ messages in thread* Re: [PATCH] powerpc/32s: Don't flush all TLBs when flushing one page
2020-01-31 15:37 [PATCH] powerpc/32s: Don't flush all TLBs when flushing one page Christophe Leroy
@ 2020-01-31 15:51 ` Segher Boessenkool
2020-01-31 16:15 ` Christophe Leroy
0 siblings, 1 reply; 8+ messages in thread
From: Segher Boessenkool @ 2020-01-31 15:51 UTC (permalink / raw)
To: Christophe Leroy
Cc: Benjamin Herrenschmidt, Paul Mackerras, Michael Ellerman,
linuxppc-dev, linux-kernel
On Fri, Jan 31, 2020 at 03:37:34PM +0000, Christophe Leroy wrote:
> When the range is a single page, do a page flush instead.
> + start &= PAGE_MASK;
> + end = (end - 1) | ~PAGE_MASK;
> if (!Hash) {
> - _tlbia();
> + if (end - start == PAGE_SIZE)
> + _tlbie(start);
> + else
> + _tlbia();
> return;
> }
For just one page, you get end - start == 0 actually?
Segher
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [PATCH] powerpc/32s: Don't flush all TLBs when flushing one page
2020-01-31 15:51 ` Segher Boessenkool
@ 2020-01-31 16:15 ` Christophe Leroy
2020-01-31 19:38 ` Segher Boessenkool
0 siblings, 1 reply; 8+ messages in thread
From: Christophe Leroy @ 2020-01-31 16:15 UTC (permalink / raw)
To: Segher Boessenkool
Cc: Benjamin Herrenschmidt, Paul Mackerras, Michael Ellerman,
linuxppc-dev, linux-kernel
Le 31/01/2020 à 16:51, Segher Boessenkool a écrit :
> On Fri, Jan 31, 2020 at 03:37:34PM +0000, Christophe Leroy wrote:
>> When the range is a single page, do a page flush instead.
>
>> + start &= PAGE_MASK;
>> + end = (end - 1) | ~PAGE_MASK;
>> if (!Hash) {
>> - _tlbia();
>> + if (end - start == PAGE_SIZE)
>> + _tlbie(start);
>> + else
>> + _tlbia();
>> return;
>> }
>
> For just one page, you get end - start == 0 actually?
>
>
Oops, good catch.
Indeed you don't get PAGE_SIZE but (PAGE_SIZE - 1) for just one page.
Christophe
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [PATCH] powerpc/32s: Don't flush all TLBs when flushing one page
2020-01-31 16:15 ` Christophe Leroy
@ 2020-01-31 19:38 ` Segher Boessenkool
2020-02-01 7:27 ` Christophe Leroy
0 siblings, 1 reply; 8+ messages in thread
From: Segher Boessenkool @ 2020-01-31 19:38 UTC (permalink / raw)
To: Christophe Leroy
Cc: Benjamin Herrenschmidt, Paul Mackerras, Michael Ellerman,
linuxppc-dev, linux-kernel
On Fri, Jan 31, 2020 at 05:15:20PM +0100, Christophe Leroy wrote:
> Le 31/01/2020 à 16:51, Segher Boessenkool a écrit :
> >On Fri, Jan 31, 2020 at 03:37:34PM +0000, Christophe Leroy wrote:
> >>When the range is a single page, do a page flush instead.
> >
> >>+ start &= PAGE_MASK;
> >>+ end = (end - 1) | ~PAGE_MASK;
> >> if (!Hash) {
> >>- _tlbia();
> >>+ if (end - start == PAGE_SIZE)
> >>+ _tlbie(start);
> >>+ else
> >>+ _tlbia();
> >> return;
> >> }
> >
> >For just one page, you get end - start == 0 actually?
>
> Oops, good catch.
>
> Indeed you don't get PAGE_SIZE but (PAGE_SIZE - 1) for just one page.
You have all low bits masked off in both start and end, so you get zero.
You could make the condion read "if (start == end)?
Maybe a nicer way to describe what you do is "if start and end are on the
same memory page, flush that page."
Segher
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [PATCH] powerpc/32s: Don't flush all TLBs when flushing one page
2020-01-31 19:38 ` Segher Boessenkool
@ 2020-02-01 7:27 ` Christophe Leroy
2020-02-01 14:06 ` Segher Boessenkool
0 siblings, 1 reply; 8+ messages in thread
From: Christophe Leroy @ 2020-02-01 7:27 UTC (permalink / raw)
To: Segher Boessenkool
Cc: Benjamin Herrenschmidt, Paul Mackerras, Michael Ellerman,
linuxppc-dev, linux-kernel
Le 31/01/2020 à 20:38, Segher Boessenkool a écrit :
> On Fri, Jan 31, 2020 at 05:15:20PM +0100, Christophe Leroy wrote:
>> Le 31/01/2020 à 16:51, Segher Boessenkool a écrit :
>>> On Fri, Jan 31, 2020 at 03:37:34PM +0000, Christophe Leroy wrote:
>>>> When the range is a single page, do a page flush instead.
>>>
>>>> + start &= PAGE_MASK;
>>>> + end = (end - 1) | ~PAGE_MASK;
>>>> if (!Hash) {
>>>> - _tlbia();
>>>> + if (end - start == PAGE_SIZE)
>>>> + _tlbie(start);
>>>> + else
>>>> + _tlbia();
>>>> return;
>>>> }
>>>
>>> For just one page, you get end - start == 0 actually?
>>
>> Oops, good catch.
>>
>> Indeed you don't get PAGE_SIZE but (PAGE_SIZE - 1) for just one page.
>
> You have all low bits masked off in both start and end, so you get zero.
> You could make the condion read "if (start == end)?
No, in end the low bits are set, that's a BIT OR with ~PAGE_MASK, so it
sets all low bits to 1.
Christophe
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [PATCH] powerpc/32s: Don't flush all TLBs when flushing one page
2020-02-01 7:27 ` Christophe Leroy
@ 2020-02-01 14:06 ` Segher Boessenkool
2020-02-01 14:53 ` Christophe Leroy
0 siblings, 1 reply; 8+ messages in thread
From: Segher Boessenkool @ 2020-02-01 14:06 UTC (permalink / raw)
To: Christophe Leroy
Cc: Benjamin Herrenschmidt, Paul Mackerras, Michael Ellerman,
linuxppc-dev, linux-kernel
On Sat, Feb 01, 2020 at 08:27:03AM +0100, Christophe Leroy wrote:
> Le 31/01/2020 à 20:38, Segher Boessenkool a écrit :
> >On Fri, Jan 31, 2020 at 05:15:20PM +0100, Christophe Leroy wrote:
> >>Le 31/01/2020 à 16:51, Segher Boessenkool a écrit :
> >>>On Fri, Jan 31, 2020 at 03:37:34PM +0000, Christophe Leroy wrote:
> >>>>When the range is a single page, do a page flush instead.
> >>>
> >>>>+ start &= PAGE_MASK;
> >>>>+ end = (end - 1) | ~PAGE_MASK;
> >>>> if (!Hash) {
> >>>>- _tlbia();
> >>>>+ if (end - start == PAGE_SIZE)
> >>>>+ _tlbie(start);
> >>>>+ else
> >>>>+ _tlbia();
> >>>> return;
> >>>> }
> >>>
> >>>For just one page, you get end - start == 0 actually?
> >>
> >>Oops, good catch.
> >>
> >>Indeed you don't get PAGE_SIZE but (PAGE_SIZE - 1) for just one page.
> >
> >You have all low bits masked off in both start and end, so you get zero.
> >You could make the condion read "if (start == end)?
>
> No, in end the low bits are set, that's a BIT OR with ~PAGE_MASK, so it
> sets all low bits to 1.
Oh, wow, yes, I cannot read apparently.
Maybe there are some ROUND_DOWN and ROUND_UP macros you could use?
Segher
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [PATCH] powerpc/32s: Don't flush all TLBs when flushing one page
2020-02-01 14:06 ` Segher Boessenkool
@ 2020-02-01 14:53 ` Christophe Leroy
2020-02-01 16:17 ` Segher Boessenkool
0 siblings, 1 reply; 8+ messages in thread
From: Christophe Leroy @ 2020-02-01 14:53 UTC (permalink / raw)
To: Segher Boessenkool
Cc: Benjamin Herrenschmidt, Paul Mackerras, Michael Ellerman,
linuxppc-dev, linux-kernel
Le 01/02/2020 à 15:06, Segher Boessenkool a écrit :
> On Sat, Feb 01, 2020 at 08:27:03AM +0100, Christophe Leroy wrote:
>> Le 31/01/2020 à 20:38, Segher Boessenkool a écrit :
>>> On Fri, Jan 31, 2020 at 05:15:20PM +0100, Christophe Leroy wrote:
>>>> Le 31/01/2020 à 16:51, Segher Boessenkool a écrit :
>>>>> On Fri, Jan 31, 2020 at 03:37:34PM +0000, Christophe Leroy wrote:
>>>>>> When the range is a single page, do a page flush instead.
>>>>>
>>>>>> + start &= PAGE_MASK;
>>>>>> + end = (end - 1) | ~PAGE_MASK;
>>>>>> if (!Hash) {
>>>>>> - _tlbia();
>>>>>> + if (end - start == PAGE_SIZE)
>>>>>> + _tlbie(start);
>>>>>> + else
>>>>>> + _tlbia();
>>>>>> return;
>>>>>> }
>>>>>
>>>>> For just one page, you get end - start == 0 actually?
>>>>
>>>> Oops, good catch.
>>>>
>>>> Indeed you don't get PAGE_SIZE but (PAGE_SIZE - 1) for just one page.
>>>
>>> You have all low bits masked off in both start and end, so you get zero.
>>> You could make the condion read "if (start == end)?
>>
>> No, in end the low bits are set, that's a BIT OR with ~PAGE_MASK, so it
>> sets all low bits to 1.
>
> Oh, wow, yes, I cannot read apparently.
>
> Maybe there are some ROUND_DOWN and ROUND_UP macros you could use?
>
Yes but my intention was to modify the existing code as less as possible.
What do you think about version v2 of the patch ?
Christophe
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [PATCH] powerpc/32s: Don't flush all TLBs when flushing one page
2020-02-01 14:53 ` Christophe Leroy
@ 2020-02-01 16:17 ` Segher Boessenkool
0 siblings, 0 replies; 8+ messages in thread
From: Segher Boessenkool @ 2020-02-01 16:17 UTC (permalink / raw)
To: Christophe Leroy
Cc: Benjamin Herrenschmidt, Paul Mackerras, Michael Ellerman,
linuxppc-dev, linux-kernel
On Sat, Feb 01, 2020 at 03:53:12PM +0100, Christophe Leroy wrote:
> >>No, in end the low bits are set, that's a BIT OR with ~PAGE_MASK, so it
> >>sets all low bits to 1.
> >
> >Oh, wow, yes, I cannot read apparently.
> >
> >Maybe there are some ROUND_DOWN and ROUND_UP macros you could use?
>
> Yes but my intention was to modify the existing code as less as possible.
> What do you think about version v2 of the patch ?
It looked fine to me.
Add my
Reviewed-by: Segher Boessenkool <segher@kernel.crashing.org>
if you want.
Segher
^ permalink raw reply [flat|nested] 8+ messages in thread
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2020-01-31 15:37 [PATCH] powerpc/32s: Don't flush all TLBs when flushing one page Christophe Leroy
2020-01-31 15:51 ` Segher Boessenkool
2020-01-31 16:15 ` Christophe Leroy
2020-01-31 19:38 ` Segher Boessenkool
2020-02-01 7:27 ` Christophe Leroy
2020-02-01 14:06 ` Segher Boessenkool
2020-02-01 14:53 ` Christophe Leroy
2020-02-01 16:17 ` Segher Boessenkool
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