On Tue, Oct 11, 2011 at 1:17 AM, David Daney <david.daney@xxxxxxxxxx> wrote:
> On 10/09/2011 05:53 AM, Hillf Danton wrote:
>>
>> When flushing TLB, if @vma is backed by huge page, huge TLB should be
>> flushed,
>> due to the fact that huge page is defined to be far from normal page, and
>> the
>> flushing is shorten a bit.
>>
>> Any comment is welcome.
>>
>
> Note that the current implementation works, but is not optimal.
>
>> Thanks
>>
>> Signed-off-by: Hillf Danton<dhillf@xxxxxxxxx>
>> ---
>>
>> --- a/arch/mips/mm/tlb-r4k.c Mon May 30 21:17:04 2011
>> +++ b/arch/mips/mm/tlb-r4k.c Sun Oct 9 20:50:06 2011
>> @@ -120,22 +120,35 @@ void local_flush_tlb_range(struct vm_are
>>
>> if (cpu_context(cpu, mm) != 0) {
>> unsigned long size, flags;
>> + int huge = is_vm_hugetlb_page(vma);
>>
>> ENTER_CRITICAL(flags);
>> - size = (end - start + (PAGE_SIZE - 1))>> PAGE_SHIFT;
>> - size = (size + 1)>> 1;
>> + if (huge) {
>> + size = (end - start) / HPAGE_SIZE;
>
>> + } else {
>> + size = (end - start + (PAGE_SIZE - 1))>>
>> PAGE_SHIFT;
>> + size = (size + 1)>> 1;
>> + }
>
> Perhaps:
> if (huge) {
> start = round_down(start, HPAGE_SIZE);
> end = round_up(start, HPAGE_SIZE);
> size = (end - start) >> HPAGE_SHIFT;
> } else {
> start = round_down(start, PAGE_SIZE << 1);
> end = round_up(start, PAGE_SIZE << 1);
> size = (end - start) >> (PAGE_SHIFT + 1);
> }
> .
> .
> .
>
>> if (size<= current_cpu_data.tlbsize/2) {
>
> Has anybody benchmarked this heuristic? I guess it seems reasonable.
>
>> int oldpid = read_c0_entryhi();
>> int newpid = cpu_asid(cpu, mm);
>>
>> - start&= (PAGE_MASK<< 1);
>> - end += ((PAGE_SIZE<< 1) - 1);
>> - end&= (PAGE_MASK<< 1);
>> + if (huge) {
>> + start&= HPAGE_MASK;
>> + end&= HPAGE_MASK;
>> + } else {
>> + start&= (PAGE_MASK<< 1);
>> + end += ((PAGE_SIZE<< 1) - 1);
>> + end&= (PAGE_MASK<< 1);
>> + }
>
> This stuff is done above so is removed.
>
>
>> while (start< end) {
>> int idx;
>>
>> write_c0_entryhi(start | newpid);
>> - start += (PAGE_SIZE<< 1);
>> + if (huge)
>> + start += HPAGE_SIZE;
>> + else
>> + start += (PAGE_SIZE<< 1);
>> mtc0_tlbw_hazard();
>> tlb_probe();
>> tlb_probe_hazard();
>>
>>
>
> If we do something like that, then...
>
> Acked-by: David Daney <david.daney@xxxxxxxxxx>
>
Thanks David. It is re-prepared as the following.
----------------------------------------------------------------------------
Subject: Flush huge TLB
From: Hillf Danton <dhillf@xxxxxxxxx>
When flushing TLB, if @vma is backed by huge page, we could flush huge TLB,
due to that huge page is defined to be far from normal page.
Signed-off-by: Hillf Danton <dhillf@xxxxxxxxx>
Acked-by: David Daney <david.daney@xxxxxxxxxx>
---
--- a/arch/mips/mm/tlb-r4k.c Mon May 30 21:17:04 2011
+++ b/arch/mips/mm/tlb-r4k.c Sun Oct 9 20:50:06 2011
@@ -120,22 +120,30 @@ void local_flush_tlb_range(struct vm_are
if (cpu_context(cpu, mm) != 0) {
unsigned long size, flags;
+ int huge = is_vm_hugetlb_page(vma);
ENTER_CRITICAL(flags);
- size = (end - start + (PAGE_SIZE - 1)) >> PAGE_SHIFT;
- size = (size + 1) >> 1;
+ if (huge) {
+ start = round_down(start, HPAGE_SIZE);
+ end = round_up(end, HPAGE_SIZE);
+ size = (end - start) >> HPAGE_SHIFT;
+ } else {
+ start = round_down(start, PAGE_SIZE << 1);
+ end = round_up(end, PAGE_SIZE << 1);
+ size = (end - start) >> (PAGE_SHIFT + 1);
+ }
if (size <= current_cpu_data.tlbsize/2) {
int oldpid = read_c0_entryhi();
int newpid = cpu_asid(cpu, mm);
- start &= (PAGE_MASK << 1);
- end += ((PAGE_SIZE << 1) - 1);
- end &= (PAGE_MASK << 1);
while (start < end) {
int idx;
write_c0_entryhi(start | newpid);
- start += (PAGE_SIZE << 1);
+ if (huge)
+ start += HPAGE_SIZE;
+ else
+ start += (PAGE_SIZE << 1);
mtc0_tlbw_hazard();
tlb_probe();
tlb_probe_hazard();
