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-rw-r--r--erts/emulator/beam/erl_alloc_util.c45
1 files changed, 30 insertions, 15 deletions
diff --git a/erts/emulator/beam/erl_alloc_util.c b/erts/emulator/beam/erl_alloc_util.c
index d1335598b0..6ce872895b 100644
--- a/erts/emulator/beam/erl_alloc_util.c
+++ b/erts/emulator/beam/erl_alloc_util.c
@@ -118,7 +118,34 @@ static Uint max_mseg_carriers;
? ((CC).giga_no--, (CC).no = ONE_GIGA - 1) \
: (CC).no--)
-/* ... */
+/* Multi block carrier (MBC) memory layout in R16:
+
+Empty MBC:
+[Carrier_t|pad|Block_t L0T|fhdr| free... ]
+
+MBC after allocating first block:
+[Carrier_t|pad|Block_t 000| udata |pad|Block_t L0T|fhdr| free... ]
+
+MBC after allocating second block:
+[Carrier_t|pad|Block_t 000| udata |pad|Block_t 000| udata |pad|Block_t L0T|fhdr| free... ]
+
+MBC after deallocating first block:
+[Carrier_t|pad|Block_t 00T|fhdr| free |FreeBlkFtr_t|Block_t 0P0| udata |pad|Block_t L0T|fhdr| free... ]
+
+
+ udata = Allocated user data
+ pad = Padding to ensure correct alignment for user data
+ fhdr = Allocator specific header to keep track of free block
+ free = Unused free memory
+ T = This block is free (THIS_FREE_BLK_HDR_FLG)
+ P = Previous block is free (PREV_FREE_BLK_HDR_FLG)
+ L = Last block in carrier (LAST_BLK_HDR_FLG)
+*/
+
+/* Single block carrier (SBC):
+[Carrier_t|pad|Block_t 111| udata... ]
+*/
+
/* Blocks ... */
@@ -137,8 +164,7 @@ static Uint max_mseg_carriers;
#define UMEM2BLK(P) ((Block_t *) (((char *) (P)) - ABLK_HDR_SZ))
#define BLK2UMEM(P) ((void *) (((char *) (P)) + ABLK_HDR_SZ))
-#define PREV_BLK_SZ(B) \
- ((UWord) (((FreeBlkFtr_t *)(B))[-1] & MBC_BLK_SZ_MASK))
+#define PREV_BLK_SZ(B) ((UWord) (((FreeBlkFtr_t *)(B))[-1]))
#define SET_BLK_SZ_FTR(B, SZ) \
(((FreeBlkFtr_t *) (((char *) (B)) + (SZ)))[-1] = (SZ))
@@ -239,11 +265,6 @@ static Uint max_mseg_carriers;
#define GET_BLK_HDR_FLGS(B) \
((B)->bhdr & FLG_MASK)
-#define SET_SBC_BLK_FTR(FTR) \
- ((FTR) = 0)
-#define SET_MBC_BLK_FTR(FTR) \
- ((FTR) = 0)
-
#define IS_SBC_BLK(B) \
(((B)->bhdr & FLG_MASK) == SBC_BLK_HDR_FLG)
#define IS_MBC_BLK(B) \
@@ -258,9 +279,7 @@ static Uint max_mseg_carriers;
/* Carriers ... */
-#define SIZEOF_SBC_HDR (UNIT_CEILING(sizeof(Carrier_t) \
- + FBLK_FTR_SZ \
- + ABLK_HDR_SZ) \
+#define SIZEOF_SBC_HDR (UNIT_CEILING(sizeof(Carrier_t) + ABLK_HDR_SZ) \
- ABLK_HDR_SZ)
#define MSEG_CARRIER_HDR_FLAG (((UWord) 1) << 0)
@@ -1894,7 +1913,6 @@ create_sbmbc(Allctr_t *allctr, Uint umem_sz)
blk_sz = UNIT_FLOOR(crr_sz - allctr->mbc_header_size);
- SET_MBC_BLK_FTR(((FreeBlkFtr_t *) blk)[-1]);
SET_MBC_BLK_HDR(blk, blk_sz, SBH_THIS_FREE|SBH_LAST_BLK, crr);
link_carrier(&allctr->sbmbc_list, crr);
@@ -2077,7 +2095,6 @@ create_carrier(Allctr_t *allctr, Uint umem_sz, UWord flags)
blk = SBC2BLK(allctr, crr);
- SET_SBC_BLK_FTR(((FreeBlkFtr_t *) blk)[-1]);
SET_SBC_BLK_HDR(blk, blk_sz);
link_carrier(&allctr->sbc_list, crr);
@@ -2097,7 +2114,6 @@ create_carrier(Allctr_t *allctr, Uint umem_sz, UWord flags)
blk_sz = UNIT_FLOOR(crr_sz - allctr->mbc_header_size);
- SET_MBC_BLK_FTR(((FreeBlkFtr_t *) blk)[-1]);
SET_MBC_BLK_HDR(blk, blk_sz, SBH_THIS_FREE|SBH_LAST_BLK, crr);
if (flags & CFLG_MAIN_CARRIER) {
@@ -4178,7 +4194,6 @@ erts_alcu_start(Allctr_t *allctr, AllctrInit_t *init)
}
#endif
allctr->mbc_header_size = (UNIT_CEILING(allctr->mbc_header_size
- + FBLK_FTR_SZ
+ ABLK_HDR_SZ)
- ABLK_HDR_SZ);
allctr->sbc_header_size = SIZEOF_SBC_HDR;