diff options
Diffstat (limited to '')
| -rw-r--r-- | gc/include/private/gc_hdrs.h | 98 |
1 files changed, 98 insertions, 0 deletions
diff --git a/gc/include/private/gc_hdrs.h b/gc/include/private/gc_hdrs.h index 60dc2ad..dd61545 100644 --- a/gc/include/private/gc_hdrs.h +++ b/gc/include/private/gc_hdrs.h @@ -24,6 +24,15 @@ typedef struct hblkhdr hdr; * The 2 level tree data structure that is used to find block headers. * If there are more than 32 bits in a pointer, the top level is a hash * table. + * + * This defines HDR, GET_HDR, and SET_HDR, the main macros used to + * retrieve and set object headers. + * + * Since 5.0 alpha 5, we can also take advantage of a header lookup + * cache. This is a locally declared direct mapped cache, used inside + * the marker. The HC_GET_HDR macro uses and maintains this + * cache. Assuming we get reasonable hit rates, this shaves a few + * memory references from each pointer validation. */ # if CPP_WORDSZ > 32 @@ -45,6 +54,95 @@ typedef struct hblkhdr hdr; # define TOP_SZ (1 << LOG_TOP_SZ) # define BOTTOM_SZ (1 << LOG_BOTTOM_SZ) +#ifndef SMALL_CONFIG +# define USE_HDR_CACHE +#endif + +/* #define COUNT_HDR_CACHE_HITS */ + +extern hdr * GC_invalid_header; /* header for an imaginary block */ + /* containing no objects. */ + + +/* Check whether p and corresponding hhdr point to long or invalid */ +/* object. If so, advance hhdr to */ +/* beginning of block, or set hhdr to GC_invalid_header. */ +#define ADVANCE(p, hhdr, source) \ + { \ + hdr * new_hdr = GC_invalid_header; \ + p = GC_FIND_START(p, hhdr, &new_hdr, (word)source); \ + hhdr = new_hdr; \ + } + +#ifdef USE_HDR_CACHE + +# ifdef COUNT_HDR_CACHE_HITS + extern word GC_hdr_cache_hits; + extern word GC_hdr_cache_misses; +# define HC_HIT() ++GC_hdr_cache_hits +# define HC_MISS() ++GC_hdr_cache_misses +# else +# define HC_HIT() +# define HC_MISS() +# endif + + typedef struct hce { + word block_addr; /* right shifted by LOG_HBLKSIZE */ + hdr * hce_hdr; + } hdr_cache_entry; + +# define HDR_CACHE_SIZE 8 /* power of 2 */ + +# define DECLARE_HDR_CACHE \ + hdr_cache_entry hdr_cache[HDR_CACHE_SIZE] + +# define INIT_HDR_CACHE BZERO(hdr_cache, sizeof(hdr_cache)); + +# define HCE(h) hdr_cache + (((word)(h) >> LOG_HBLKSIZE) & (HDR_CACHE_SIZE-1)) + +# define HCE_VALID_FOR(hce,h) ((hce) -> block_addr == \ + ((word)(h) >> LOG_HBLKSIZE)) + +# define HCE_HDR(h) ((hce) -> hce_hdr) + + +/* Analogous to GET_HDR, except that in the case of large objects, it */ +/* Returns the header for the object beginning, and updates p. */ +/* Returns &GC_bad_header instead of 0. All of this saves a branch */ +/* in the fast path. */ +# define HC_GET_HDR(p, hhdr, source) \ + { \ + hdr_cache_entry * hce = HCE(p); \ + if (HCE_VALID_FOR(hce, p)) { \ + HC_HIT(); \ + hhdr = hce -> hce_hdr; \ + } else { \ + HC_MISS(); \ + GET_HDR(p, hhdr); \ + if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) { \ + ADVANCE(p, hhdr, source); \ + } else { \ + hce -> block_addr = (word)(p) >> LOG_HBLKSIZE; \ + hce -> hce_hdr = hhdr; \ + } \ + } \ + } + +#else /* !USE_HDR_CACHE */ + +# define DECLARE_HDR_CACHE + +# define INIT_HDR_CACHE + +# define HC_GET_HDR(p, hhdr, source) \ + { \ + GET_HDR(p, hhdr); \ + if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) { \ + ADVANCE(p, hhdr, source); \ + } \ + } +#endif + typedef struct bi { hdr * index[BOTTOM_SZ]; /* |