fb4e5dbd44
With split PTL (page table lock) config, we allocate the level
4 (leaf) page table using pte fragment framework instead of slab cache
like other levels. This was done to enable us to have split page table
lock at the level 4 of the page table. We use page->plt backing the
all the level 4 pte fragment for the lock.
Currently with Radix, we use only 16 fragments out of the allocated
page. In radix each fragment is 256 bytes which means we use only 4k
out of the allocated 64K page wasting 60k of the allocated memory.
This was done earlier to keep it closer to hash.
This patch update the pte fragment count to 256, thereby using the
full 64K page and reducing the memory usage. Performance tests shows
really low impact even with THP disabled. With THP disabled we will be
contenting further less on level 4 ptl and hence the impact should be
further low.
256 threads:
without patch (10 runs of ./ebizzy -m -n 1000 -s 131072 -S 100)
median = 15678.5
stdev = 42.1209
with patch:
median = 15354
stdev = 194.743
This is with THP disabled. With THP enabled the impact of the patch
will be less.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
19 lines
610 B
C
19 lines
610 B
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_POWERPC_PGTABLE_RADIX_64K_H
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#define _ASM_POWERPC_PGTABLE_RADIX_64K_H
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/*
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* For 64K page size supported index is 13/9/9/5
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*/
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#define RADIX_PTE_INDEX_SIZE 5 /* 2MB huge page */
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#define RADIX_PMD_INDEX_SIZE 9 /* 1G huge page */
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#define RADIX_PUD_INDEX_SIZE 9
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#define RADIX_PGD_INDEX_SIZE 13
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/*
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* We use a 256 byte PTE page fragment in radix
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* 8 bytes per each PTE entry.
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*/
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#define RADIX_PTE_FRAG_SIZE_SHIFT (RADIX_PTE_INDEX_SIZE + 3)
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#define RADIX_PTE_FRAG_NR (PAGE_SIZE >> RADIX_PTE_FRAG_SIZE_SHIFT)
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#endif /* _ASM_POWERPC_PGTABLE_RADIX_64K_H */
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