Subject: Re: [PATCH -V5 24/25] powerpc: Optimize hugepage invalidate

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Sun, 14 Apr 2013 15:32:12 +0530

David Gibson <[email-masked]> writes:

> On Thu, Apr 04, 2013 at 11:28:02AM +0530, Aneesh Kumar K.V wrote:
>> From: "Aneesh Kumar K.V" <[email-masked]>
>> 
>> Hugepage invalidate involves invalidating multiple hpte entries.
>> Optimize the operation using H_BULK_REMOVE on lpar platforms.
>> On native, reduce the number of tlb flush.
>> 
>> Signed-off-by: Aneesh Kumar K.V <[email-masked]>
>> ---
>>  arch/powerpc/include/asm/machdep.h    |    3 +
>>  arch/powerpc/mm/hash_native_64.c      |   78 ++++++++++++++++++++
>>  arch/powerpc/mm/pgtable.c             |   13 +++-
>>  arch/powerpc/platforms/pseries/lpar.c |  126 +++++++++++++++++++++++++++++++--
>>  4 files changed, 210 insertions(+), 10 deletions(-)
>> 
>> diff --git a/arch/powerpc/include/asm/machdep.h b/arch/powerpc/include/asm/machdep.h
>> index 6cee6e0..3bc7816 100644
>> --- a/arch/powerpc/include/asm/machdep.h
>> +++ b/arch/powerpc/include/asm/machdep.h
>> @@ -56,6 +56,9 @@ struct machdep_calls {
>>  	void            (*hpte_removebolted)(unsigned long ea,
>>  					     int psize, int ssize);
>>  	void		(*flush_hash_range)(unsigned long number, int local);
>> +	void		(*hugepage_invalidate)(struct mm_struct *mm,
>> +					       unsigned char *hpte_slot_array,
>> +					       unsigned long addr, int psize);
>>  
>>  	/* special for kexec, to be called in real mode, linear mapping is
>>  	 * destroyed as well */
>> diff --git a/arch/powerpc/mm/hash_native_64.c b/arch/powerpc/mm/hash_native_64.c
>> index ac84fa6..59f29bf 100644
>> --- a/arch/powerpc/mm/hash_native_64.c
>> +++ b/arch/powerpc/mm/hash_native_64.c
>> @@ -450,6 +450,83 @@ static void native_hpte_invalidate(unsigned long slot, unsigned long vpn,
>>  	local_irq_restore(flags);
>>  }
>>  
>> +static void native_hugepage_invalidate(struct mm_struct *mm,
>> +				       unsigned char *hpte_slot_array,
>> +				       unsigned long addr, int psize)
>> +{
>> +	int ssize = 0, i;
>> +	int lock_tlbie;
>> +	struct hash_pte *hptep;
>> +	int actual_psize = MMU_PAGE_16M;
>> +	unsigned int max_hpte_count, valid;
>> +	unsigned long flags, s_addr = addr;
>> +	unsigned long hpte_v, want_v, shift;
>> +	unsigned long hidx, vpn = 0, vsid, hash, slot;
>> +
>> +	shift = mmu_psize_defs[psize].shift;
>> +	max_hpte_count = HUGE_PAGE_SIZE/(1ul << shift);
>> +
>> +	local_irq_save(flags);
>> +	for (i = 0; i < max_hpte_count; i++) {
>> +		/*
>> +		 * 8 bits per each hpte entries
>> +		 * 000| [ secondary group (one bit) | hidx (3 bits) | valid bit]
>> +		 */
>> +		valid = hpte_slot_array[i] & 0x1;
>> +		if (!valid)
>> +			continue;
>> +		hidx =  hpte_slot_array[i]  >> 1;
>> +
>> +		/* get the vpn */
>> +		addr = s_addr + (i * (1ul << shift));
>> +		if (!is_kernel_addr(addr)) {
>> +			ssize = user_segment_size(addr);
>> +			vsid = get_vsid(mm->context.id, addr, ssize);
>> +			WARN_ON(vsid == 0);
>> +		} else {
>> +			vsid = get_kernel_vsid(addr, mmu_kernel_ssize);
>> +			ssize = mmu_kernel_ssize;
>> +		}
>> +
>> +		vpn = hpt_vpn(addr, vsid, ssize);
>> +		hash = hpt_hash(vpn, shift, ssize);
>> +		if (hidx & _PTEIDX_SECONDARY)
>> +			hash = ~hash;
>> +
>> +		slot = (hash & htab_hash_mask) * HPTES_PER_GROUP;
>> +		slot += hidx & _PTEIDX_GROUP_IX;
>> +
>> +		hptep = htab_address + slot;
>> +		want_v = hpte_encode_avpn(vpn, psize, ssize);
>> +		native_lock_hpte(hptep);
>> +		hpte_v = hptep->v;
>> +
>> +		/* Even if we miss, we need to invalidate the TLB */
>> +		if (!HPTE_V_COMPARE(hpte_v, want_v) || !(hpte_v & HPTE_V_VALID))
>> +			native_unlock_hpte(hptep);
>> +		else
>> +			/* Invalidate the hpte. NOTE: this also unlocks it */
>> +			hptep->v = 0;
>
> Shouldn't you be clearing the entry from the slot_array once it is
> invalidated in the hash table?

We don't need to do that. We should be fine even if hptes get
invalidated under us. Also inorder to update slot_array i will have to
mark the corresponding hpte busy, so that we can ensure nobody is
looking at the slot array.

>
>> +	}
>> +	/*
>> +	 * Since this is a hugepage, we just need a single tlbie.
>> +	 * use the last vpn.
>> +	 */
>> +	lock_tlbie = !mmu_has_feature(MMU_FTR_LOCKLESS_TLBIE);
>> +	if (lock_tlbie)
>> +		raw_spin_lock(&native_tlbie_lock);
>> +
>> +	asm volatile("ptesync":::"memory");
>> +	__tlbie(vpn, psize, actual_psize, ssize);
>> +	asm volatile("eieio; tlbsync; ptesync":::"memory");
>> +
>> +	if (lock_tlbie)
>> +		raw_spin_unlock(&native_tlbie_lock);
>> +
>> +	local_irq_restore(flags);
>> +}
>> +
>> +
>>  static void hpte_decode(struct hash_pte *hpte, unsigned long slot,
>>  			int *psize, int *apsize, int *ssize, unsigned long *vpn)
>>  {
>> @@ -678,4 +755,5 @@ void __init hpte_init_native(void)
>>  	ppc_md.hpte_remove	= native_hpte_remove;
>>  	ppc_md.hpte_clear_all	= native_hpte_clear;
>>  	ppc_md.flush_hash_range = native_flush_hash_range;
>> +	ppc_md.hugepage_invalidate   = native_hugepage_invalidate;
>>  }
>> diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c
>> index fbff062..386cab8 100644
>> --- a/arch/powerpc/mm/pgtable.c
>> +++ b/arch/powerpc/mm/pgtable.c
>> @@ -433,6 +433,7 @@ void hpte_need_hugepage_flush(struct mm_struct *mm, unsigned long addr,
>>  {
>>  	int ssize, i;
>>  	unsigned long s_addr;
>> +	int max_hpte_count;
>>  	unsigned int psize, valid;
>>  	unsigned char *hpte_slot_array;
>>  	unsigned long hidx, vpn, vsid, hash, shift, slot;
>> @@ -446,12 +447,18 @@ void hpte_need_hugepage_flush(struct mm_struct *mm, unsigned long addr,
>>  	 * second half of the PMD
>>  	 */
>>  	hpte_slot_array = *(char **)(pmdp + PTRS_PER_PMD);
>> -
>>  	/* get the base page size */
>>  	psize = get_slice_psize(mm, s_addr);
>> -	shift = mmu_psize_defs[psize].shift;
>>  
>> -	for (i = 0; i < HUGE_PAGE_SIZE/(1ul << shift); i++) {
>> +	if (ppc_md.hugepage_invalidate)
>> +		return ppc_md.hugepage_invalidate(mm, hpte_slot_array,
>> +						  s_addr, psize);
>> +	/*
>> +	 * No bluk hpte removal support, invalidate each entry
>> +	 */
>> +	shift = mmu_psize_defs[psize].shift;
>> +	max_hpte_count = HUGE_PAGE_SIZE/(1ul << shift);
>> +	for (i = 0; i < max_hpte_count; i++) {
>>  		/*
>>  		 * 8 bits per each hpte entries
>>  		 * 000| [ secondary group (one bit) | hidx (3 bits) | valid bit]
>> diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c
>> index 3daced3..5fcc621 100644
>> --- a/arch/powerpc/platforms/pseries/lpar.c
>> +++ b/arch/powerpc/platforms/pseries/lpar.c
>> @@ -45,6 +45,13 @@
>>  #include "plpar_wrappers.h"
>>  #include "pseries.h"
>>  
>> +/* Flag bits for H_BULK_REMOVE */
>> +#define HBR_REQUEST	0x4000000000000000UL
>> +#define HBR_RESPONSE	0x8000000000000000UL
>> +#define HBR_END		0xc000000000000000UL
>> +#define HBR_AVPN	0x0200000000000000UL
>> +#define HBR_ANDCOND	0x0100000000000000UL
>> +
>>  
>>  /* in hvCall.S */
>>  EXPORT_SYMBOL(plpar_hcall);
>> @@ -339,6 +346,117 @@ static void pSeries_lpar_hpte_invalidate(unsigned long slot, unsigned long vpn,
>>  	BUG_ON(lpar_rc != H_SUCCESS);
>>  }
>>  
>> +/*
>> + * Limit iterations holding pSeries_lpar_tlbie_lock to 3. We also need
>> + * to make sure that we avoid bouncing the hypervisor tlbie lock.
>> + */
>> +#define PPC64_HUGE_HPTE_BATCH 12
>> +
>> +static void __pSeries_lpar_hugepage_invalidate(unsigned long *slot,
>> +					     unsigned long *vpn, int count,
>> +					     int psize, int ssize)
>> +{
>> +	unsigned long param[9];
>> +	int i = 0, pix = 0, rc;
>> +	unsigned long flags = 0;
>> +	int lock_tlbie = !mmu_has_feature(MMU_FTR_LOCKLESS_TLBIE);
>> +
>> +	if (lock_tlbie)
>> +		spin_lock_irqsave(&pSeries_lpar_tlbie_lock, flags);
>> +
>> +	for (i = 0; i < count; i++) {
>> +
>> +		if (!firmware_has_feature(FW_FEATURE_BULK_REMOVE)) {
>> +			pSeries_lpar_hpte_invalidate(slot[i], vpn[i], psize,
>> +						     ssize, 0);
>> +		} else {
>> +			param[pix] = HBR_REQUEST | HBR_AVPN | slot[i];
>> +			param[pix+1] = hpte_encode_avpn(vpn[i], psize, ssize);
>> +			pix += 2;
>> +			if (pix == 8) {
>> +				rc = plpar_hcall9(H_BULK_REMOVE, param,
>> +						  param[0], param[1], param[2],
>> +						  param[3], param[4], param[5],
>> +						  param[6], param[7]);
>> +				BUG_ON(rc != H_SUCCESS);
>> +				pix = 0;
>> +			}
>> +		}
>> +	}
>> +	if (pix) {
>> +		param[pix] = HBR_END;
>> +		rc = plpar_hcall9(H_BULK_REMOVE, param, param[0], param[1],
>> +				  param[2], param[3], param[4], param[5],
>> +				  param[6], param[7]);
>> +		BUG_ON(rc != H_SUCCESS);
>> +	}
>> +
>> +	if (lock_tlbie)
>> +		spin_unlock_irqrestore(&pSeries_lpar_tlbie_lock, flags);
>> +}
>> +
>> +static void pSeries_lpar_hugepage_invalidate(struct mm_struct *mm,
>> +				       unsigned char *hpte_slot_array,
>> +				       unsigned long addr, int psize)
>> +{
>> +	int ssize = 0, i, index = 0;
>> +	unsigned long s_addr = addr;
>> +	unsigned int max_hpte_count, valid;
>> +	unsigned long vpn_array[PPC64_HUGE_HPTE_BATCH];
>> +	unsigned long slot_array[PPC64_HUGE_HPTE_BATCH];
>
> These are really too big to be allocating on the stack.  You'd be
> better off going direct from the char slot array to the data structure
> for H_BULK_REMOVE, rather than introducing this intermediate
> structure.

The reason i wanted to do that was to make sure i don't lock/unlock
pSeries_lpar_tlbie_lock that frequently, ie, for ever H_BULK_REMOVE.
The total size taken by both the array is only 192 bytes. Is that big
enough to create trouble ?

>
>> +	unsigned long shift, hidx, vpn = 0, vsid, hash, slot;
>> +
>> +	shift = mmu_psize_defs[psize].shift;
>> +	max_hpte_count = HUGE_PAGE_SIZE/(1ul << shift);
>> +
>> +	for (i = 0; i < max_hpte_count; i++) {
>> +		/*
>> +		 * 8 bits per each hpte entries
>> +		 * 000| [ secondary group (one bit) | hidx (3 bits) | valid bit]
>> +		 */
>> +		valid = hpte_slot_array[i] & 0x1;
>> +		if (!valid)
>> +			continue;
>> +		hidx =  hpte_slot_array[i]  >> 1;
>> +
>> +		/* get the vpn */
>> +		addr = s_addr + (i * (1ul << shift));
>> +		if (!is_kernel_addr(addr)) {
>> +			ssize = user_segment_size(addr);
>> +			vsid = get_vsid(mm->context.id, addr, ssize);
>> +			WARN_ON(vsid == 0);
>> +		} else {
>> +			vsid = get_kernel_vsid(addr, mmu_kernel_ssize);
>> +			ssize = mmu_kernel_ssize;
>> +		}
>> +
>> +		vpn = hpt_vpn(addr, vsid, ssize);
>> +		hash = hpt_hash(vpn, shift, ssize);
>> +		if (hidx & _PTEIDX_SECONDARY)
>> +			hash = ~hash;
>> +
>> +		slot = (hash & htab_hash_mask) * HPTES_PER_GROUP;
>> +		slot += hidx & _PTEIDX_GROUP_IX;
>> +
>> +		slot_array[index] = slot;
>> +		vpn_array[index] = vpn;
>> +		if (index == PPC64_HUGE_HPTE_BATCH - 1) {
>> +			/*
>> +			 * Now do a bluk invalidate
>> +			 */
>> +			__pSeries_lpar_hugepage_invalidate(slot_array,
>> +							   vpn_array,
>> +							   PPC64_HUGE_HPTE_BATCH,
>> +							   psize, ssize);
>> +			index = 0;
>> +		} else
>> +			index++;
>> +	}
>> +	if (index)
>> +		__pSeries_lpar_hugepage_invalidate(slot_array, vpn_array,
>> +						   index, psize, ssize);
>> +}
>> +
>>  static void pSeries_lpar_hpte_removebolted(unsigned long ea,
>>  					   int psize, int ssize)
>>  {
>> @@ -354,13 +472,6 @@ static void pSeries_lpar_hpte_removebolted(unsigned long ea,
>>  	pSeries_lpar_hpte_invalidate(slot, vpn, psize, ssize, 0);
>>  }
>>  
>> -/* Flag bits for H_BULK_REMOVE */
>> -#define HBR_REQUEST	0x4000000000000000UL
>> -#define HBR_RESPONSE	0x8000000000000000UL
>> -#define HBR_END		0xc000000000000000UL
>> -#define HBR_AVPN	0x0200000000000000UL
>> -#define HBR_ANDCOND	0x0100000000000000UL
>> -
>>  /*
>>   * Take a spinlock around flushes to avoid bouncing the hypervisor tlbie
>>   * lock.
>> @@ -446,6 +557,7 @@ void __init hpte_init_lpar(void)
>>  	ppc_md.hpte_removebolted = pSeries_lpar_hpte_removebolted;
>>  	ppc_md.flush_hash_range	= pSeries_lpar_flush_hash_range;
>>  	ppc_md.hpte_clear_all   = pSeries_lpar_hptab_clear;
>> +	ppc_md.hugepage_invalidate = pSeries_lpar_hugepage_invalidate;
>>  }
>>  
>>  #ifdef CONFIG_PPC_SMLPAR

-aneesh