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Diffstat (limited to 'deps/jemalloc/src/sc.c')
| -rw-r--r-- | deps/jemalloc/src/sc.c | 313 |
1 files changed, 313 insertions, 0 deletions
diff --git a/deps/jemalloc/src/sc.c b/deps/jemalloc/src/sc.c new file mode 100644 index 0000000..89ddb6b --- /dev/null +++ b/deps/jemalloc/src/sc.c @@ -0,0 +1,313 @@ +#include "jemalloc/internal/jemalloc_preamble.h" + +#include "jemalloc/internal/assert.h" +#include "jemalloc/internal/bit_util.h" +#include "jemalloc/internal/bitmap.h" +#include "jemalloc/internal/pages.h" +#include "jemalloc/internal/sc.h" + +/* + * This module computes the size classes used to satisfy allocations. The logic + * here was ported more or less line-by-line from a shell script, and because of + * that is not the most idiomatic C. Eventually we should fix this, but for now + * at least the damage is compartmentalized to this file. + */ + +sc_data_t sc_data_global; + +static size_t +reg_size_compute(int lg_base, int lg_delta, int ndelta) { + return (ZU(1) << lg_base) + (ZU(ndelta) << lg_delta); +} + +/* Returns the number of pages in the slab. */ +static int +slab_size(int lg_page, int lg_base, int lg_delta, int ndelta) { + size_t page = (ZU(1) << lg_page); + size_t reg_size = reg_size_compute(lg_base, lg_delta, ndelta); + + size_t try_slab_size = page; + size_t try_nregs = try_slab_size / reg_size; + size_t perfect_slab_size = 0; + bool perfect = false; + /* + * This loop continues until we find the least common multiple of the + * page size and size class size. Size classes are all of the form + * base + ndelta * delta == (ndelta + base/ndelta) * delta, which is + * (ndelta + ngroup) * delta. The way we choose slabbing strategies + * means that delta is at most the page size and ndelta < ngroup. So + * the loop executes for at most 2 * ngroup - 1 iterations, which is + * also the bound on the number of pages in a slab chosen by default. + * With the current default settings, this is at most 7. + */ + while (!perfect) { + perfect_slab_size = try_slab_size; + size_t perfect_nregs = try_nregs; + try_slab_size += page; + try_nregs = try_slab_size / reg_size; + if (perfect_slab_size == perfect_nregs * reg_size) { + perfect = true; + } + } + return (int)(perfect_slab_size / page); +} + +static void +size_class( + /* Output. */ + sc_t *sc, + /* Configuration decisions. */ + int lg_max_lookup, int lg_page, int lg_ngroup, + /* Inputs specific to the size class. */ + int index, int lg_base, int lg_delta, int ndelta) { + sc->index = index; + sc->lg_base = lg_base; + sc->lg_delta = lg_delta; + sc->ndelta = ndelta; + sc->psz = (reg_size_compute(lg_base, lg_delta, ndelta) + % (ZU(1) << lg_page) == 0); + size_t size = (ZU(1) << lg_base) + (ZU(ndelta) << lg_delta); + if (index == 0) { + assert(!sc->psz); + } + if (size < (ZU(1) << (lg_page + lg_ngroup))) { + sc->bin = true; + sc->pgs = slab_size(lg_page, lg_base, lg_delta, ndelta); + } else { + sc->bin = false; + sc->pgs = 0; + } + if (size <= (ZU(1) << lg_max_lookup)) { + sc->lg_delta_lookup = lg_delta; + } else { + sc->lg_delta_lookup = 0; + } +} + +static void +size_classes( + /* Output. */ + sc_data_t *sc_data, + /* Determined by the system. */ + size_t lg_ptr_size, int lg_quantum, + /* Configuration decisions. */ + int lg_tiny_min, int lg_max_lookup, int lg_page, int lg_ngroup) { + int ptr_bits = (1 << lg_ptr_size) * 8; + int ngroup = (1 << lg_ngroup); + int ntiny = 0; + int nlbins = 0; + int lg_tiny_maxclass = (unsigned)-1; + int nbins = 0; + int npsizes = 0; + + int index = 0; + + int ndelta = 0; + int lg_base = lg_tiny_min; + int lg_delta = lg_base; + + /* Outputs that we update as we go. */ + size_t lookup_maxclass = 0; + size_t small_maxclass = 0; + int lg_large_minclass = 0; + size_t large_maxclass = 0; + + /* Tiny size classes. */ + while (lg_base < lg_quantum) { + sc_t *sc = &sc_data->sc[index]; + size_class(sc, lg_max_lookup, lg_page, lg_ngroup, index, + lg_base, lg_delta, ndelta); + if (sc->lg_delta_lookup != 0) { + nlbins = index + 1; + } + if (sc->psz) { + npsizes++; + } + if (sc->bin) { + nbins++; + } + ntiny++; + /* Final written value is correct. */ + lg_tiny_maxclass = lg_base; + index++; + lg_delta = lg_base; + lg_base++; + } + + /* First non-tiny (pseudo) group. */ + if (ntiny != 0) { + sc_t *sc = &sc_data->sc[index]; + /* + * See the note in sc.h; the first non-tiny size class has an + * unusual encoding. + */ + lg_base--; + ndelta = 1; + size_class(sc, lg_max_lookup, lg_page, lg_ngroup, index, + lg_base, lg_delta, ndelta); + index++; + lg_base++; + lg_delta++; + if (sc->psz) { + npsizes++; + } + if (sc->bin) { + nbins++; + } + } + while (ndelta < ngroup) { + sc_t *sc = &sc_data->sc[index]; + size_class(sc, lg_max_lookup, lg_page, lg_ngroup, index, + lg_base, lg_delta, ndelta); + index++; + ndelta++; + if (sc->psz) { + npsizes++; + } + if (sc->bin) { + nbins++; + } + } + + /* All remaining groups. */ + lg_base = lg_base + lg_ngroup; + while (lg_base < ptr_bits - 1) { + ndelta = 1; + int ndelta_limit; + if (lg_base == ptr_bits - 2) { + ndelta_limit = ngroup - 1; + } else { + ndelta_limit = ngroup; + } + while (ndelta <= ndelta_limit) { + sc_t *sc = &sc_data->sc[index]; + size_class(sc, lg_max_lookup, lg_page, lg_ngroup, index, + lg_base, lg_delta, ndelta); + if (sc->lg_delta_lookup != 0) { + nlbins = index + 1; + /* Final written value is correct. */ + lookup_maxclass = (ZU(1) << lg_base) + + (ZU(ndelta) << lg_delta); + } + if (sc->psz) { + npsizes++; + } + if (sc->bin) { + nbins++; + /* Final written value is correct. */ + small_maxclass = (ZU(1) << lg_base) + + (ZU(ndelta) << lg_delta); + if (lg_ngroup > 0) { + lg_large_minclass = lg_base + 1; + } else { + lg_large_minclass = lg_base + 2; + } + } + large_maxclass = (ZU(1) << lg_base) + + (ZU(ndelta) << lg_delta); + index++; + ndelta++; + } + lg_base++; + lg_delta++; + } + /* Additional outputs. */ + int nsizes = index; + unsigned lg_ceil_nsizes = lg_ceil(nsizes); + + /* Fill in the output data. */ + sc_data->ntiny = ntiny; + sc_data->nlbins = nlbins; + sc_data->nbins = nbins; + sc_data->nsizes = nsizes; + sc_data->lg_ceil_nsizes = lg_ceil_nsizes; + sc_data->npsizes = npsizes; + sc_data->lg_tiny_maxclass = lg_tiny_maxclass; + sc_data->lookup_maxclass = lookup_maxclass; + sc_data->small_maxclass = small_maxclass; + sc_data->lg_large_minclass = lg_large_minclass; + sc_data->large_minclass = (ZU(1) << lg_large_minclass); + sc_data->large_maxclass = large_maxclass; + + /* + * We compute these values in two ways: + * - Incrementally, as above. + * - In macros, in sc.h. + * The computation is easier when done incrementally, but putting it in + * a constant makes it available to the fast paths without having to + * touch the extra global cacheline. We assert, however, that the two + * computations are equivalent. + */ + assert(sc_data->npsizes == SC_NPSIZES); + assert(sc_data->lg_tiny_maxclass == SC_LG_TINY_MAXCLASS); + assert(sc_data->small_maxclass == SC_SMALL_MAXCLASS); + assert(sc_data->large_minclass == SC_LARGE_MINCLASS); + assert(sc_data->lg_large_minclass == SC_LG_LARGE_MINCLASS); + assert(sc_data->large_maxclass == SC_LARGE_MAXCLASS); + + /* + * In the allocation fastpath, we want to assume that we can + * unconditionally subtract the requested allocation size from + * a ssize_t, and detect passing through 0 correctly. This + * results in optimal generated code. For this to work, the + * maximum allocation size must be less than SSIZE_MAX. + */ + assert(SC_LARGE_MAXCLASS < SSIZE_MAX); +} + +void +sc_data_init(sc_data_t *sc_data) { + assert(!sc_data->initialized); + + int lg_max_lookup = 12; + + size_classes(sc_data, LG_SIZEOF_PTR, LG_QUANTUM, SC_LG_TINY_MIN, + lg_max_lookup, LG_PAGE, 2); + + sc_data->initialized = true; +} + +static void +sc_data_update_sc_slab_size(sc_t *sc, size_t reg_size, size_t pgs_guess) { + size_t min_pgs = reg_size / PAGE; + if (reg_size % PAGE != 0) { + min_pgs++; + } + /* + * BITMAP_MAXBITS is actually determined by putting the smallest + * possible size-class on one page, so this can never be 0. + */ + size_t max_pgs = BITMAP_MAXBITS * reg_size / PAGE; + + assert(min_pgs <= max_pgs); + assert(min_pgs > 0); + assert(max_pgs >= 1); + if (pgs_guess < min_pgs) { + sc->pgs = (int)min_pgs; + } else if (pgs_guess > max_pgs) { + sc->pgs = (int)max_pgs; + } else { + sc->pgs = (int)pgs_guess; + } +} + +void +sc_data_update_slab_size(sc_data_t *data, size_t begin, size_t end, int pgs) { + assert(data->initialized); + for (int i = 0; i < data->nsizes; i++) { + sc_t *sc = &data->sc[i]; + if (!sc->bin) { + break; + } + size_t reg_size = reg_size_compute(sc->lg_base, sc->lg_delta, + sc->ndelta); + if (begin <= reg_size && reg_size <= end) { + sc_data_update_sc_slab_size(sc, reg_size, pgs); + } + } +} + +void +sc_boot(sc_data_t *data) { + sc_data_init(data); +} |