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Commit 1753dd18 authored by Nicholas Piggin's avatar Nicholas Piggin Committed by Michael Ellerman
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powerpc/mm/slice: Simplify and optimise slice context initialisation 



The slice state of an mm gets zeroed then initialised upon exec.
This is the only caller of slice_set_user_psize now, so that can be
removed and instead implement a faster and simplified approach that
requires no locking or checking existing state.

This speeds up vfork+exec+exit performance on POWER8 by 3%.

Signed-off-by: default avatarNicholas Piggin <npiggin@gmail.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent ab83dc79

arch/powerpc/include/asm/slice.h

+3 −5
Original line number Diff line number Diff line
@@ -28,15 +28,13 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len, 


unsigned int get_slice_psize(struct mm_struct *mm, unsigned long addr);



void slice_set_user_psize(struct mm_struct *mm, unsigned int psize);

void slice_set_range_psize(struct mm_struct *mm, unsigned long start,

			   unsigned long len, unsigned int psize);

#endif /* __ASSEMBLY__ */



#else /* CONFIG_PPC_MM_SLICES */

void slice_init_new_context_exec(struct mm_struct *mm);



#endif /* __ASSEMBLY__ */



#define slice_set_range_psize(mm, start, len, psize)	\

	slice_set_user_psize((mm), (psize))

#endif /* CONFIG_PPC_MM_SLICES */



#endif /* _ASM_POWERPC_SLICE_H */

arch/powerpc/mm/mmu_context_book3s64.c

+1 −8
Original line number Diff line number Diff line
@@ -93,13 +93,6 @@ static int hash__init_new_context(struct mm_struct *mm) 
	if (index < 0)

		return index;



	/*

	 * In the case of exec, use the default limit,

	 * otherwise inherit it from the mm we are duplicating.

	 */

	if (!mm->context.slb_addr_limit)

		mm->context.slb_addr_limit = DEFAULT_MAP_WINDOW_USER64;



	/*

	 * The old code would re-promote on fork, we don't do that when using

	 * slices as it could cause problem promoting slices that have been
@@ -115,7 +108,7 @@ static int hash__init_new_context(struct mm_struct *mm) 
	 * check against 0 is OK.

	 */

	if (mm->context.id == 0)

		slice_set_user_psize(mm, mmu_virtual_psize);

		slice_init_new_context_exec(mm);



	subpage_prot_init_new_context(mm);

arch/powerpc/mm/mmu_context_nohash.c

+1 −4
Original line number Diff line number Diff line
@@ -332,9 +332,6 @@ int init_new_context(struct task_struct *t, struct mm_struct *mm) 
	pr_hard("initing context for mm @%p\n", mm);



#ifdef	CONFIG_PPC_MM_SLICES

	if (!mm->context.slb_addr_limit)

		mm->context.slb_addr_limit = DEFAULT_MAP_WINDOW;



	/*

	 * We have MMU_NO_CONTEXT set to be ~0. Hence check

	 * explicitly against context.id == 0. This ensures that we properly
@@ -343,7 +340,7 @@ int init_new_context(struct task_struct *t, struct mm_struct *mm) 
	 * will have id != 0).

	 */

	if (mm->context.id == 0)

		slice_set_user_psize(mm, mmu_virtual_psize);

		slice_init_new_context_exec(mm);

#endif

	mm->context.id = MMU_NO_CONTEXT;

	mm->context.active = 0;

arch/powerpc/mm/slice.c

+18 −54
Original line number Diff line number Diff line
@@ -671,70 +671,34 @@ unsigned int get_slice_psize(struct mm_struct *mm, unsigned long addr) 
}

EXPORT_SYMBOL_GPL(get_slice_psize);



/*

 * This is called by hash_page when it needs to do a lazy conversion of

 * an address space from real 64K pages to combo 4K pages (typically

 * when hitting a non cacheable mapping on a processor or hypervisor

 * that won't allow them for 64K pages).

 *

 * This is also called in init_new_context() to change back the user

 * psize from whatever the parent context had it set to

 * N.B. This may be called before mm->context.id has been set.

 *

 * This function will only change the content of the {low,high)_slice_psize

 * masks, it will not flush SLBs as this shall be handled lazily by the

 * caller.

 */

void slice_set_user_psize(struct mm_struct *mm, unsigned int psize)

void slice_init_new_context_exec(struct mm_struct *mm)

{

	int index, mask_index;

	unsigned char *hpsizes, *lpsizes;

	unsigned long flags;

	unsigned int old_psize;

	int i;

	unsigned int psize = mmu_virtual_psize;



	slice_dbg("slice_set_user_psize(mm=%p, psize=%d)\n", mm, psize);

	slice_dbg("slice_init_new_context_exec(mm=%p)\n", mm);



	VM_BUG_ON(radix_enabled());

	spin_lock_irqsave(&slice_convert_lock, flags);



	old_psize = mm->context.user_psize;

	slice_dbg(" old_psize=%d\n", old_psize);

	if (old_psize == psize)

		goto bail;

	/*

	 * In the case of exec, use the default limit. In the

	 * case of fork it is just inherited from the mm being

	 * duplicated.

	 */

#ifdef CONFIG_PPC64

	mm->context.slb_addr_limit = DEFAULT_MAP_WINDOW_USER64;

#else

	mm->context.slb_addr_limit = DEFAULT_MAP_WINDOW;

#endif



	mm->context.user_psize = psize;

	wmb();



	/*

	 * Set all slice psizes to the default.

	 */

	lpsizes = mm->context.low_slices_psize;

	for (i = 0; i < SLICE_NUM_LOW; i++) {

		mask_index = i & 0x1;

		index = i >> 1;

		if (((lpsizes[index] >> (mask_index * 4)) & 0xf) == old_psize)

			lpsizes[index] = (lpsizes[index] &

					  ~(0xf << (mask_index * 4))) |

				(((unsigned long)psize) << (mask_index * 4));

	}

	memset(lpsizes, (psize << 4) | psize, SLICE_NUM_LOW >> 1);



	hpsizes = mm->context.high_slices_psize;

	for (i = 0; i < SLICE_NUM_HIGH; i++) {

		mask_index = i & 0x1;

		index = i >> 1;

		if (((hpsizes[index] >> (mask_index * 4)) & 0xf) == old_psize)

			hpsizes[index] = (hpsizes[index] &

					  ~(0xf << (mask_index * 4))) |

				(((unsigned long)psize) << (mask_index * 4));

	}









	slice_dbg(" lsps=%lx, hsps=%lx\n",

		  (unsigned long)mm->context.low_slices_psize,

		  (unsigned long)mm->context.high_slices_psize);



 bail:

	spin_unlock_irqrestore(&slice_convert_lock, flags);

	memset(hpsizes, (psize << 4) | psize, SLICE_NUM_HIGH >> 1);

}



void slice_set_range_psize(struct mm_struct *mm, unsigned long start,