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powerpc/mm/slice: Simplify and optimise slice context initialisation

Telusuri Sumber 
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: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Nicholas Piggin
2018-03-07 11:37:09 +10:00
committed by Michael Ellerman
orang tua ab83dc794c
melakukan 1753dd1830
4 mengubah file dengan 23 tambahan dan 71 penghapusan
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72
arch/powerpc/mm/slice.c
Melihat File

@@ -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,