Revert "Remove BITMAP_USE_TREE."
Some systems use a native 64 KiB page size, which means that the bitmap
for the smallest size class can be 8192 bits, not just 512 bits as when
the page size is 4 KiB. Linear search in bitmap_{sfu,ffu}() is
unacceptably slow for such large bitmaps.
This reverts commit 7c00f04ff4
.
This commit is contained in:
parent
38e847c1c5
commit
45f087eb03
@ -16,6 +16,12 @@ void bitmap_unset(bitmap_t *bitmap, const bitmap_info_t *binfo, size_t bit);
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#if (defined(JEMALLOC_ENABLE_INLINE) || defined(JEMALLOC_BITMAP_C_))
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JEMALLOC_INLINE bool
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bitmap_full(bitmap_t *bitmap, const bitmap_info_t *binfo) {
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#ifdef BITMAP_USE_TREE
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size_t rgoff = binfo->levels[binfo->nlevels].group_offset - 1;
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bitmap_t rg = bitmap[rgoff];
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/* The bitmap is full iff the root group is 0. */
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return (rg == 0);
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#else
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size_t i;
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for (i = 0; i < binfo->ngroups; i++) {
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@ -24,6 +30,7 @@ bitmap_full(bitmap_t *bitmap, const bitmap_info_t *binfo) {
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}
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}
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return true;
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#endif
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}
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JEMALLOC_INLINE bool
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@ -52,6 +59,24 @@ bitmap_set(bitmap_t *bitmap, const bitmap_info_t *binfo, size_t bit) {
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g ^= ZU(1) << (bit & BITMAP_GROUP_NBITS_MASK);
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*gp = g;
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assert(bitmap_get(bitmap, binfo, bit));
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#ifdef BITMAP_USE_TREE
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/* Propagate group state transitions up the tree. */
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if (g == 0) {
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unsigned i;
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for (i = 1; i < binfo->nlevels; i++) {
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bit = goff;
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goff = bit >> LG_BITMAP_GROUP_NBITS;
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gp = &bitmap[binfo->levels[i].group_offset + goff];
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g = *gp;
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assert(g & (ZU(1) << (bit & BITMAP_GROUP_NBITS_MASK)));
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g ^= ZU(1) << (bit & BITMAP_GROUP_NBITS_MASK);
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*gp = g;
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if (g != 0) {
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break;
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}
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}
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}
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#endif
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}
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/* ffu: find first unset >= bit. */
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@ -59,6 +84,44 @@ JEMALLOC_INLINE size_t
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bitmap_ffu(const bitmap_t *bitmap, const bitmap_info_t *binfo, size_t min_bit) {
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assert(min_bit < binfo->nbits);
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#ifdef BITMAP_USE_TREE
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size_t bit = 0;
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for (unsigned level = binfo->nlevels; level--;) {
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size_t lg_bits_per_group = (LG_BITMAP_GROUP_NBITS * (level +
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1));
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bitmap_t group = bitmap[binfo->levels[level].group_offset + (bit
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>> lg_bits_per_group)];
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unsigned group_nmask = ((min_bit > bit) ? (min_bit - bit) : 0)
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>> (lg_bits_per_group - LG_BITMAP_GROUP_NBITS);
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assert(group_nmask <= BITMAP_GROUP_NBITS);
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bitmap_t group_mask = ~((1LU << group_nmask) - 1);
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bitmap_t group_masked = group & group_mask;
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if (group_masked == 0LU) {
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if (group == 0LU) {
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return binfo->nbits;
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}
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/*
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* min_bit was preceded by one or more unset bits in
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* this group, but there are no other unset bits in this
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* group. Try again starting at the first bit of the
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* next sibling. This will recurse at most once per
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* non-root level.
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*/
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size_t sib_base = bit + (1U << lg_bits_per_group);
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assert(sib_base > min_bit);
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assert(sib_base > bit);
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if (sib_base >= binfo->nbits) {
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return binfo->nbits;
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}
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return bitmap_ffu(bitmap, binfo, sib_base);
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}
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bit += (ffs_lu(group_masked) - 1) << (lg_bits_per_group -
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LG_BITMAP_GROUP_NBITS);
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}
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assert(bit >= min_bit);
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assert(bit < binfo->nbits);
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return bit;
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#else
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size_t i = min_bit >> LG_BITMAP_GROUP_NBITS;
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bitmap_t g = bitmap[i] & ~((1LU << (min_bit & BITMAP_GROUP_NBITS_MASK))
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- 1);
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@ -72,6 +135,7 @@ bitmap_ffu(const bitmap_t *bitmap, const bitmap_info_t *binfo, size_t min_bit) {
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g = bitmap[i];
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} while (i < binfo->ngroups);
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return binfo->nbits;
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#endif
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}
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/* sfu: set first unset. */
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@ -83,6 +147,16 @@ bitmap_sfu(bitmap_t *bitmap, const bitmap_info_t *binfo) {
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assert(!bitmap_full(bitmap, binfo));
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#ifdef BITMAP_USE_TREE
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i = binfo->nlevels - 1;
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g = bitmap[binfo->levels[i].group_offset];
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bit = ffs_lu(g) - 1;
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while (i > 0) {
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i--;
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g = bitmap[binfo->levels[i].group_offset + bit];
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bit = (bit << LG_BITMAP_GROUP_NBITS) + (ffs_lu(g) - 1);
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}
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#else
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i = 0;
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g = bitmap[0];
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while ((bit = ffs_lu(g)) == 0) {
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@ -90,6 +164,7 @@ bitmap_sfu(bitmap_t *bitmap, const bitmap_info_t *binfo) {
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g = bitmap[i];
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}
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bit = (i << LG_BITMAP_GROUP_NBITS) + (bit - 1);
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#endif
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bitmap_set(bitmap, binfo, bit);
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return bit;
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}
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@ -111,6 +186,26 @@ bitmap_unset(bitmap_t *bitmap, const bitmap_info_t *binfo, size_t bit) {
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g ^= ZU(1) << (bit & BITMAP_GROUP_NBITS_MASK);
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*gp = g;
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assert(!bitmap_get(bitmap, binfo, bit));
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#ifdef BITMAP_USE_TREE
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/* Propagate group state transitions up the tree. */
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if (propagate) {
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unsigned i;
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for (i = 1; i < binfo->nlevels; i++) {
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bit = goff;
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goff = bit >> LG_BITMAP_GROUP_NBITS;
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gp = &bitmap[binfo->levels[i].group_offset + goff];
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g = *gp;
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propagate = (g == 0);
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assert((g & (ZU(1) << (bit & BITMAP_GROUP_NBITS_MASK)))
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== 0);
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g ^= ZU(1) << (bit & BITMAP_GROUP_NBITS_MASK);
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*gp = g;
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if (!propagate) {
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break;
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}
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}
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}
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#endif /* BITMAP_USE_TREE */
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}
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#endif
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@ -10,8 +10,19 @@ struct bitmap_info_s {
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/* Logical number of bits in bitmap (stored at bottom level). */
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size_t nbits;
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#ifdef BITMAP_USE_TREE
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/* Number of levels necessary for nbits. */
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unsigned nlevels;
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/*
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* Only the first (nlevels+1) elements are used, and levels are ordered
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* bottom to top (e.g. the bottom level is stored in levels[0]).
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*/
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bitmap_level_t levels[BITMAP_MAX_LEVELS+1];
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#else /* BITMAP_USE_TREE */
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/* Number of groups necessary for nbits. */
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size_t ngroups;
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#endif /* BITMAP_USE_TREE */
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};
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#endif /* JEMALLOC_INTERNAL_BITMAP_STRUCTS_H */
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@ -21,10 +21,115 @@ typedef unsigned long bitmap_t;
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#define BITMAP_GROUP_NBITS (1U << LG_BITMAP_GROUP_NBITS)
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#define BITMAP_GROUP_NBITS_MASK (BITMAP_GROUP_NBITS-1)
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/*
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* Do some analysis on how big the bitmap is before we use a tree. For a brute
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* force linear search, if we would have to call ffs_lu() more than 2^3 times,
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* use a tree instead.
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*/
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#if LG_BITMAP_MAXBITS - LG_BITMAP_GROUP_NBITS > 3
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# define BITMAP_USE_TREE
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#endif
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/* Number of groups required to store a given number of bits. */
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#define BITMAP_BITS2GROUPS(nbits) \
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(((nbits) + BITMAP_GROUP_NBITS_MASK) >> LG_BITMAP_GROUP_NBITS)
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/*
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* Number of groups required at a particular level for a given number of bits.
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*/
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#define BITMAP_GROUPS_L0(nbits) \
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BITMAP_BITS2GROUPS(nbits)
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#define BITMAP_GROUPS_L1(nbits) \
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BITMAP_BITS2GROUPS(BITMAP_BITS2GROUPS(nbits))
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#define BITMAP_GROUPS_L2(nbits) \
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BITMAP_BITS2GROUPS(BITMAP_BITS2GROUPS(BITMAP_BITS2GROUPS((nbits))))
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#define BITMAP_GROUPS_L3(nbits) \
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BITMAP_BITS2GROUPS(BITMAP_BITS2GROUPS(BITMAP_BITS2GROUPS( \
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BITMAP_BITS2GROUPS((nbits)))))
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#define BITMAP_GROUPS_L4(nbits) \
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BITMAP_BITS2GROUPS(BITMAP_BITS2GROUPS(BITMAP_BITS2GROUPS( \
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BITMAP_BITS2GROUPS(BITMAP_BITS2GROUPS((nbits))))))
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/*
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* Assuming the number of levels, number of groups required for a given number
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* of bits.
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*/
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#define BITMAP_GROUPS_1_LEVEL(nbits) \
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BITMAP_GROUPS_L0(nbits)
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#define BITMAP_GROUPS_2_LEVEL(nbits) \
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(BITMAP_GROUPS_1_LEVEL(nbits) + BITMAP_GROUPS_L1(nbits))
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#define BITMAP_GROUPS_3_LEVEL(nbits) \
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(BITMAP_GROUPS_2_LEVEL(nbits) + BITMAP_GROUPS_L2(nbits))
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#define BITMAP_GROUPS_4_LEVEL(nbits) \
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(BITMAP_GROUPS_3_LEVEL(nbits) + BITMAP_GROUPS_L3(nbits))
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#define BITMAP_GROUPS_5_LEVEL(nbits) \
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(BITMAP_GROUPS_4_LEVEL(nbits) + BITMAP_GROUPS_L4(nbits))
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/*
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* Maximum number of groups required to support LG_BITMAP_MAXBITS.
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*/
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#ifdef BITMAP_USE_TREE
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#if LG_BITMAP_MAXBITS <= LG_BITMAP_GROUP_NBITS
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# define BITMAP_GROUPS(nbits) BITMAP_GROUPS_1_LEVEL(nbits)
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# define BITMAP_GROUPS_MAX BITMAP_GROUPS_1_LEVEL(BITMAP_MAXBITS)
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#elif LG_BITMAP_MAXBITS <= LG_BITMAP_GROUP_NBITS * 2
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# define BITMAP_GROUPS(nbits) BITMAP_GROUPS_2_LEVEL(nbits)
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# define BITMAP_GROUPS_MAX BITMAP_GROUPS_2_LEVEL(BITMAP_MAXBITS)
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#elif LG_BITMAP_MAXBITS <= LG_BITMAP_GROUP_NBITS * 3
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# define BITMAP_GROUPS(nbits) BITMAP_GROUPS_3_LEVEL(nbits)
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# define BITMAP_GROUPS_MAX BITMAP_GROUPS_3_LEVEL(BITMAP_MAXBITS)
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#elif LG_BITMAP_MAXBITS <= LG_BITMAP_GROUP_NBITS * 4
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# define BITMAP_GROUPS(nbits) BITMAP_GROUPS_4_LEVEL(nbits)
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# define BITMAP_GROUPS_MAX BITMAP_GROUPS_4_LEVEL(BITMAP_MAXBITS)
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#elif LG_BITMAP_MAXBITS <= LG_BITMAP_GROUP_NBITS * 5
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# define BITMAP_GROUPS(nbits) BITMAP_GROUPS_5_LEVEL(nbits)
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# define BITMAP_GROUPS_MAX BITMAP_GROUPS_5_LEVEL(BITMAP_MAXBITS)
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#else
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# error "Unsupported bitmap size"
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#endif
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/*
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* Maximum number of levels possible. This could be statically computed based
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* on LG_BITMAP_MAXBITS:
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*
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* #define BITMAP_MAX_LEVELS \
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* (LG_BITMAP_MAXBITS / LG_SIZEOF_BITMAP) \
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* + !!(LG_BITMAP_MAXBITS % LG_SIZEOF_BITMAP)
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*
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* However, that would not allow the generic BITMAP_INFO_INITIALIZER() macro, so
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* instead hardcode BITMAP_MAX_LEVELS to the largest number supported by the
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* various cascading macros. The only additional cost this incurs is some
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* unused trailing entries in bitmap_info_t structures; the bitmaps themselves
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* are not impacted.
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*/
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#define BITMAP_MAX_LEVELS 5
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#define BITMAP_INFO_INITIALIZER(nbits) { \
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/* nbits. */ \
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nbits, \
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/* nlevels. */ \
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(BITMAP_GROUPS_L0(nbits) > BITMAP_GROUPS_L1(nbits)) + \
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(BITMAP_GROUPS_L1(nbits) > BITMAP_GROUPS_L2(nbits)) + \
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(BITMAP_GROUPS_L2(nbits) > BITMAP_GROUPS_L3(nbits)) + \
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(BITMAP_GROUPS_L3(nbits) > BITMAP_GROUPS_L4(nbits)) + 1, \
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/* levels. */ \
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{ \
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{0}, \
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{BITMAP_GROUPS_L0(nbits)}, \
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{BITMAP_GROUPS_L1(nbits) + BITMAP_GROUPS_L0(nbits)}, \
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{BITMAP_GROUPS_L2(nbits) + BITMAP_GROUPS_L1(nbits) + \
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BITMAP_GROUPS_L0(nbits)}, \
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{BITMAP_GROUPS_L3(nbits) + BITMAP_GROUPS_L2(nbits) + \
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BITMAP_GROUPS_L1(nbits) + BITMAP_GROUPS_L0(nbits)}, \
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{BITMAP_GROUPS_L4(nbits) + BITMAP_GROUPS_L3(nbits) + \
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BITMAP_GROUPS_L2(nbits) + BITMAP_GROUPS_L1(nbits) \
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+ BITMAP_GROUPS_L0(nbits)} \
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} \
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}
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#else /* BITMAP_USE_TREE */
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#define BITMAP_GROUPS(nbits) BITMAP_BITS2GROUPS(nbits)
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#define BITMAP_GROUPS_MAX BITMAP_BITS2GROUPS(BITMAP_MAXBITS)
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@ -35,4 +140,6 @@ typedef unsigned long bitmap_t;
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BITMAP_BITS2GROUPS(nbits) \
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}
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#endif /* BITMAP_USE_TREE */
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#endif /* JEMALLOC_INTERNAL_BITMAP_TYPES_H */
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78
src/bitmap.c
78
src/bitmap.c
@ -6,6 +6,82 @@
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/******************************************************************************/
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#ifdef BITMAP_USE_TREE
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void
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bitmap_info_init(bitmap_info_t *binfo, size_t nbits) {
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unsigned i;
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size_t group_count;
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assert(nbits > 0);
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assert(nbits <= (ZU(1) << LG_BITMAP_MAXBITS));
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/*
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* Compute the number of groups necessary to store nbits bits, and
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* progressively work upward through the levels until reaching a level
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* that requires only one group.
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*/
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binfo->levels[0].group_offset = 0;
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group_count = BITMAP_BITS2GROUPS(nbits);
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for (i = 1; group_count > 1; i++) {
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assert(i < BITMAP_MAX_LEVELS);
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binfo->levels[i].group_offset = binfo->levels[i-1].group_offset
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+ group_count;
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group_count = BITMAP_BITS2GROUPS(group_count);
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}
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binfo->levels[i].group_offset = binfo->levels[i-1].group_offset
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+ group_count;
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assert(binfo->levels[i].group_offset <= BITMAP_GROUPS_MAX);
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binfo->nlevels = i;
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binfo->nbits = nbits;
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}
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static size_t
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bitmap_info_ngroups(const bitmap_info_t *binfo) {
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return binfo->levels[binfo->nlevels].group_offset;
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}
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void
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bitmap_init(bitmap_t *bitmap, const bitmap_info_t *binfo, bool fill) {
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size_t extra;
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unsigned i;
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/*
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* Bits are actually inverted with regard to the external bitmap
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* interface.
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*/
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if (fill) {
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/* The "filled" bitmap starts out with all 0 bits. */
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memset(bitmap, 0, bitmap_size(binfo));
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return;
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}
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/*
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* The "empty" bitmap starts out with all 1 bits, except for trailing
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* unused bits (if any). Note that each group uses bit 0 to correspond
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* to the first logical bit in the group, so extra bits are the most
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* significant bits of the last group.
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*/
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memset(bitmap, 0xffU, bitmap_size(binfo));
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extra = (BITMAP_GROUP_NBITS - (binfo->nbits & BITMAP_GROUP_NBITS_MASK))
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& BITMAP_GROUP_NBITS_MASK;
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if (extra != 0) {
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bitmap[binfo->levels[1].group_offset - 1] >>= extra;
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}
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for (i = 1; i < binfo->nlevels; i++) {
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size_t group_count = binfo->levels[i].group_offset -
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binfo->levels[i-1].group_offset;
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extra = (BITMAP_GROUP_NBITS - (group_count &
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BITMAP_GROUP_NBITS_MASK)) & BITMAP_GROUP_NBITS_MASK;
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if (extra != 0) {
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bitmap[binfo->levels[i+1].group_offset - 1] >>= extra;
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}
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}
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}
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#else /* BITMAP_USE_TREE */
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void
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bitmap_info_init(bitmap_info_t *binfo, size_t nbits) {
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assert(nbits > 0);
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@ -37,6 +113,8 @@ bitmap_init(bitmap_t *bitmap, const bitmap_info_t *binfo, bool fill) {
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}
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}
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#endif /* BITMAP_USE_TREE */
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size_t
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bitmap_size(const bitmap_info_t *binfo) {
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return (bitmap_info_ngroups(binfo) << LG_SIZEOF_BITMAP);
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@ -103,8 +103,24 @@ test_bitmap_initializer_body(const bitmap_info_t *binfo, size_t nbits) {
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assert_zu_eq(binfo->nbits, binfo_dyn.nbits,
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"Unexpected difference between static and dynamic initialization, "
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"nbits=%zu", nbits);
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#ifdef BITMAP_USE_TREE
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assert_u_eq(binfo->nlevels, binfo_dyn.nlevels,
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"Unexpected difference between static and dynamic initialization, "
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"nbits=%zu", nbits);
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{
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unsigned i;
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for (i = 0; i < binfo->nlevels; i++) {
|
||||
assert_zu_eq(binfo->levels[i].group_offset,
|
||||
binfo_dyn.levels[i].group_offset,
|
||||
"Unexpected difference between static and dynamic "
|
||||
"initialization, nbits=%zu, level=%u", nbits, i);
|
||||
}
|
||||
}
|
||||
#else
|
||||
assert_zu_eq(binfo->ngroups, binfo_dyn.ngroups,
|
||||
"Unexpected difference between static and dynamic initialization");
|
||||
#endif
|
||||
}
|
||||
|
||||
TEST_BEGIN(test_bitmap_initializer) {
|
||||
|
Loading…
Reference in New Issue
Block a user