[RFC v3 01/23] powerpc: Free up four 64K PTE bits in 4K backed HPTE pages
From: Ram Pai
Date: Wed Jun 21 2017 - 21:40:00 EST
Rearrange 64K PTE bits to free up bits 3, 4, 5 and 6,
in the 4K backed HPTE pages. These bits continue to be used
for 64K backed HPTE pages in this patch, but will be freed
up in the next patch. The bit numbers are big-endian as
defined in the ISA3.0
The patch does the following change to the 64K PTE format
H_PAGE_BUSY moves from bit 3 to bit 9
H_PAGE_F_SECOND which occupied bit 4 moves to the second part
of the pte.
H_PAGE_F_GIX which occupied bit 5, 6 and 7 also moves to the
second part of the pte.
the four bits((H_PAGE_F_SECOND|H_PAGE_F_GIX) that represent a slot
is initialized to 0xF indicating an invalid slot. If a HPTE
gets cached in a 0xF slot(i.e 7th slot of secondary), it is
released immediately. In other words, even though 0xF is a
valid slot we discard and consider it as an invalid
slot;i.e HPTE(). This gives us an opportunity to not
depend on a bit in the primary PTE in order to determine the
validity of a slot.
When we release a HPTE in the 0xF slot we also release a
legitimate primary slot and unmap that entry. This is to
ensure that we do get a legimate non-0xF slot the next time we
retry for a slot.
Though treating 0xF slot as invalid reduces the number of available
slots and may have an effect on the performance, the probabilty
of hitting a 0xF is extermely low.
Compared to the current scheme, the above described scheme reduces
the number of false hash table updates significantly and has the
added advantage of releasing four valuable PTE bits for other
purpose.
This idea was jointly developed by Paul Mackerras, Aneesh, Michael
Ellermen and myself.
4K PTE format remain unchanged currently.
Signed-off-by: Ram Pai <linuxram@xxxxxxxxxx>
Conflicts:
arch/powerpc/include/asm/book3s/64/hash.h
---
arch/powerpc/include/asm/book3s/64/hash-4k.h | 7 +++
arch/powerpc/include/asm/book3s/64/hash-64k.h | 17 ++++---
arch/powerpc/include/asm/book3s/64/hash.h | 12 +++--
arch/powerpc/mm/hash64_64k.c | 70 +++++++++++++++------------
arch/powerpc/mm/hash_utils_64.c | 4 +-
5 files changed, 66 insertions(+), 44 deletions(-)
diff --git a/arch/powerpc/include/asm/book3s/64/hash-4k.h b/arch/powerpc/include/asm/book3s/64/hash-4k.h
index b4b5e6b..9c2c8f1 100644
--- a/arch/powerpc/include/asm/book3s/64/hash-4k.h
+++ b/arch/powerpc/include/asm/book3s/64/hash-4k.h
@@ -16,6 +16,13 @@
#define H_PUD_TABLE_SIZE (sizeof(pud_t) << H_PUD_INDEX_SIZE)
#define H_PGD_TABLE_SIZE (sizeof(pgd_t) << H_PGD_INDEX_SIZE)
+#define H_PAGE_F_SECOND _RPAGE_RSV2 /* HPTE is in 2ndary HPTEG */
+#define H_PAGE_F_GIX (_RPAGE_RSV3 | _RPAGE_RSV4 | _RPAGE_RPN44)
+#define H_PAGE_F_GIX_SHIFT 56
+
+#define H_PAGE_BUSY _RPAGE_RSV1 /* software: PTE & hash are busy */
+#define H_PAGE_HASHPTE _RPAGE_RPN43 /* PTE has associated HPTE */
+
/* PTE flags to conserve for HPTE identification */
#define _PAGE_HPTEFLAGS (H_PAGE_BUSY | H_PAGE_HASHPTE | \
H_PAGE_F_SECOND | H_PAGE_F_GIX)
diff --git a/arch/powerpc/include/asm/book3s/64/hash-64k.h b/arch/powerpc/include/asm/book3s/64/hash-64k.h
index 9732837..3f49941 100644
--- a/arch/powerpc/include/asm/book3s/64/hash-64k.h
+++ b/arch/powerpc/include/asm/book3s/64/hash-64k.h
@@ -10,20 +10,21 @@
* 64k aligned address free up few of the lower bits of RPN for us
* We steal that here. For more deatils look at pte_pfn/pfn_pte()
*/
-#define H_PAGE_COMBO _RPAGE_RPN0 /* this is a combo 4k page */
-#define H_PAGE_4K_PFN _RPAGE_RPN1 /* PFN is for a single 4k page */
+#define H_PAGE_COMBO _RPAGE_RPN0 /* this is a combo 4k page */
+#define H_PAGE_4K_PFN _RPAGE_RPN1 /* PFN is for a single 4k page */
+#define H_PAGE_F_SECOND _RPAGE_RSV2 /* HPTE is in 2ndary HPTEG */
+#define H_PAGE_F_GIX (_RPAGE_RSV3 | _RPAGE_RSV4 | _RPAGE_RPN44)
+#define H_PAGE_F_GIX_SHIFT 56
+
+#define H_PAGE_BUSY _RPAGE_RPN42 /* software: PTE & hash are busy */
+#define H_PAGE_HASHPTE _RPAGE_RPN43 /* PTE has associated HPTE */
+
/*
* We need to differentiate between explicit huge page and THP huge
* page, since THP huge page also need to track real subpage details
*/
#define H_PAGE_THP_HUGE H_PAGE_4K_PFN
-/*
- * Used to track subpage group valid if H_PAGE_COMBO is set
- * This overloads H_PAGE_F_GIX and H_PAGE_F_SECOND
- */
-#define H_PAGE_COMBO_VALID (H_PAGE_F_GIX | H_PAGE_F_SECOND)
-
/* PTE flags to conserve for HPTE identification */
#define _PAGE_HPTEFLAGS (H_PAGE_BUSY | H_PAGE_F_SECOND | \
H_PAGE_F_GIX | H_PAGE_HASHPTE | H_PAGE_COMBO)
diff --git a/arch/powerpc/include/asm/book3s/64/hash.h b/arch/powerpc/include/asm/book3s/64/hash.h
index 4e957b0..ac049de 100644
--- a/arch/powerpc/include/asm/book3s/64/hash.h
+++ b/arch/powerpc/include/asm/book3s/64/hash.h
@@ -8,11 +8,8 @@
*
*/
#define H_PTE_NONE_MASK _PAGE_HPTEFLAGS
-#define H_PAGE_F_GIX_SHIFT 56
-#define H_PAGE_BUSY _RPAGE_RSV1 /* software: PTE & hash are busy */
-#define H_PAGE_F_SECOND _RPAGE_RSV2 /* HPTE is in 2ndary HPTEG */
-#define H_PAGE_F_GIX (_RPAGE_RSV3 | _RPAGE_RSV4 | _RPAGE_RPN44)
-#define H_PAGE_HASHPTE _RPAGE_RPN43 /* PTE has associated HPTE */
+
+#define INIT_HIDX (~0x0UL)
#ifdef CONFIG_PPC_64K_PAGES
#include <asm/book3s/64/hash-64k.h>
@@ -160,6 +157,11 @@ static inline int hash__pte_none(pte_t pte)
return (pte_val(pte) & ~H_PTE_NONE_MASK) == 0;
}
+static inline bool hpte_soft_invalid(unsigned long slot)
+{
+ return ((slot & 0xfUL) == 0xfUL);
+}
+
/* This low level function performs the actual PTE insertion
* Setting the PTE depends on the MMU type and other factors. It's
* an horrible mess that I'm not going to try to clean up now but
diff --git a/arch/powerpc/mm/hash64_64k.c b/arch/powerpc/mm/hash64_64k.c
index 1a68cb1..a16cd28 100644
--- a/arch/powerpc/mm/hash64_64k.c
+++ b/arch/powerpc/mm/hash64_64k.c
@@ -20,29 +20,7 @@
*/
bool __rpte_sub_valid(real_pte_t rpte, unsigned long index)
{
- unsigned long g_idx;
- unsigned long ptev = pte_val(rpte.pte);
-
- g_idx = (ptev & H_PAGE_COMBO_VALID) >> H_PAGE_F_GIX_SHIFT;
- index = index >> 2;
- if (g_idx & (0x1 << index))
- return true;
- else
- return false;
-}
-/*
- * index from 0 - 15
- */
-static unsigned long mark_subptegroup_valid(unsigned long ptev, unsigned long index)
-{
- unsigned long g_idx;
-
- if (!(ptev & H_PAGE_COMBO))
- return ptev;
- index = index >> 2;
- g_idx = 0x1 << index;
-
- return ptev | (g_idx << H_PAGE_F_GIX_SHIFT);
+ return !(hpte_soft_invalid(rpte.hidx >> (index << 2)));
}
int __hash_page_4K(unsigned long ea, unsigned long access, unsigned long vsid,
@@ -50,12 +28,11 @@ int __hash_page_4K(unsigned long ea, unsigned long access, unsigned long vsid,
int ssize, int subpg_prot)
{
real_pte_t rpte;
- unsigned long *hidxp;
unsigned long hpte_group;
unsigned int subpg_index;
- unsigned long rflags, pa, hidx;
+ unsigned long rflags, pa;
unsigned long old_pte, new_pte, subpg_pte;
- unsigned long vpn, hash, slot;
+ unsigned long vpn, hash, slot, gslot;
unsigned long shift = mmu_psize_defs[MMU_PAGE_4K].shift;
/*
@@ -116,8 +93,8 @@ int __hash_page_4K(unsigned long ea, unsigned long access, unsigned long vsid,
* On hash insert failure we use old pte value and we don't
* want slot information there if we have a insert failure.
*/
- old_pte &= ~(H_PAGE_HASHPTE | H_PAGE_F_GIX | H_PAGE_F_SECOND);
- new_pte &= ~(H_PAGE_HASHPTE | H_PAGE_F_GIX | H_PAGE_F_SECOND);
+ old_pte &= ~(H_PAGE_HASHPTE);
+ new_pte &= ~(H_PAGE_HASHPTE);
goto htab_insert_hpte;
}
/*
@@ -148,6 +125,15 @@ int __hash_page_4K(unsigned long ea, unsigned long access, unsigned long vsid,
}
htab_insert_hpte:
+
+ /*
+ * initialize all hidx entries to a invalid value,
+ * the first time the PTE is about to allocate
+ * a 4K hpte
+ */
+ if (!(old_pte & H_PAGE_COMBO))
+ rpte.hidx = INIT_HIDX;
+
/*
* handle H_PAGE_4K_PFN case
*/
@@ -172,15 +158,39 @@ int __hash_page_4K(unsigned long ea, unsigned long access, unsigned long vsid,
* Primary is full, try the secondary
*/
if (unlikely(slot == -1)) {
+ bool soft_invalid;
+
hpte_group = ((~hash & htab_hash_mask) * HPTES_PER_GROUP) & ~0x7UL;
slot = mmu_hash_ops.hpte_insert(hpte_group, vpn, pa,
rflags, HPTE_V_SECONDARY,
MMU_PAGE_4K, MMU_PAGE_4K,
ssize);
- if (slot == -1) {
- if (mftb() & 0x1)
+
+ soft_invalid = hpte_soft_invalid(slot);
+ if (unlikely(soft_invalid)) {
+ /* we got a valid slot from a hardware point of view.
+ * but we cannot use it, because we use this special
+ * value; as defined by hpte_soft_invalid(),
+ * to track invalid slots. We cannot use it.
+ * So invalidate it.
+ */
+ gslot = slot & _PTEIDX_GROUP_IX;
+ mmu_hash_ops.hpte_invalidate(hpte_group+gslot, vpn,
+ MMU_PAGE_4K, MMU_PAGE_4K,
+ ssize, 0);
+ }
+
+ if (unlikely(slot == -1 || soft_invalid)) {
+ /* for soft invalid slot lets ensure that we
+ * release a slot from the primary, with the
+ * hope that we will acquire that slot next
+ * time we try. This will ensure that we dont
+ * get the same soft-invalid slot.
+ */
+ if (soft_invalid || (mftb() & 0x1))
hpte_group = ((hash & htab_hash_mask) *
HPTES_PER_GROUP) & ~0x7UL;
+
mmu_hash_ops.hpte_remove(hpte_group);
/*
* FIXME!! Should be try the group from which we removed ?
diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
index f2095ce..1b494d0 100644
--- a/arch/powerpc/mm/hash_utils_64.c
+++ b/arch/powerpc/mm/hash_utils_64.c
@@ -975,8 +975,9 @@ void __init hash__early_init_devtree(void)
void __init hash__early_init_mmu(void)
{
+#ifndef CONFIG_PPC_64K_PAGES
/*
- * We have code in __hash_page_64K() and elsewhere, which assumes it can
+ * We have code in __hash_page_4K() and elsewhere, which assumes it can
* do the following:
* new_pte |= (slot << H_PAGE_F_GIX_SHIFT) & (H_PAGE_F_SECOND | H_PAGE_F_GIX);
*
@@ -987,6 +988,7 @@ void __init hash__early_init_mmu(void)
* with a BUILD_BUG_ON().
*/
BUILD_BUG_ON(H_PAGE_F_SECOND != (1ul << (H_PAGE_F_GIX_SHIFT + 3)));
+#endif /* CONFIG_PPC_64K_PAGES */
htab_init_page_sizes();
--
1.8.3.1