Translate size class computation from bash shell into C.
This is the last big step in making size classes a runtime computation rather than a configure-time one. The compile-time computation has been left in, for now, to allow assertion checking that the results are identical.
This commit is contained in:
David Goldblatt
David Goldblatt
parent
2f07e92adb
commit
4f55c0ec22
321
src/sc.c
321
src/sc.c
@ -1,62 +1,301 @@
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#include "jemalloc/internal/jemalloc_preamble.h"
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#include "jemalloc/internal/assert.h"
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#include "jemalloc/internal/bit_util.h"
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#include "jemalloc/internal/sc.h"
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#include "jemalloc/internal/size_classes.h"
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sc_data_t sc_data_global;
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static size_t
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reg_size_compute(int lg_base, int lg_delta, int ndelta) {
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return (ZU(1) << lg_base) + (ZU(ndelta) << lg_delta);
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}
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/* Returns the number of pages in the slab. */
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static int
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slab_size(int lg_page, int lg_base, int lg_delta, int ndelta) {
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size_t page = (ZU(1) << lg_page);
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size_t reg_size = reg_size_compute(lg_base, lg_delta, ndelta);
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size_t try_slab_size = page;
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size_t try_nregs = try_slab_size / reg_size;
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size_t perfect_slab_size = 0;
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bool perfect = false;
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/*
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* This loop continues until we find the least common multiple of the
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* page size and size class size. Size classes are all of the form
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* base + ndelta * delta == (ndelta + base/ndelta) * delta, which is
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* (ndelta + ngroup) * delta. The way we choose slabbing strategies
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* means that delta is at most the page size and ndelta < ngroup. So
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* the loop executes for at most 2 * ngroup - 1 iterations, which is
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* also the bound on the number of pages in a slab chosen by default.
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* With the current default settings, this is at most 7.
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*/
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while (!perfect) {
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perfect_slab_size = try_slab_size;
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size_t perfect_nregs = try_nregs;
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try_slab_size += page;
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try_nregs = try_slab_size / reg_size;
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if (perfect_slab_size == perfect_nregs * reg_size) {
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perfect = true;
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}
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}
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return (int)(perfect_slab_size / page);
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}
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static void
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fill_sc(sc_data_t *data, int index, int lg_base, int lg_delta, int ndelta,
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bool psz, bool bin, int pgs, int lg_delta_lookup) {
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sc_t *sc = &data->sc[index];
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size_class(
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/* Output. */
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sc_t *sc,
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/* Configuration decisions. */
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int lg_max_lookup, int lg_page, int lg_ngroup,
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/* Inputs specific to the size class. */
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int index, int lg_base, int lg_delta, int ndelta) {
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sc->index = index;
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sc->lg_base = lg_base;
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sc->lg_delta = lg_delta;
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sc->ndelta = ndelta;
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sc->psz = psz;
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sc->bin = bin;
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sc->pgs = pgs;
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sc->lg_delta_lookup = lg_delta_lookup;
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sc->psz = (reg_size_compute(lg_base, lg_delta, ndelta)
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% (ZU(1) << lg_page) == 0);
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size_t size = (ZU(1) << lg_base) + (ZU(ndelta) << lg_delta);
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if (index == 0) {
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assert(!sc->psz);
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}
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if (size < (ZU(1) << (lg_page + lg_ngroup))) {
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sc->bin = true;
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sc->pgs = slab_size(lg_page, lg_base, lg_delta, ndelta);
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} else {
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sc->bin = false;
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sc->pgs = 0;
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}
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if (size <= (ZU(1) << lg_max_lookup)) {
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sc->lg_delta_lookup = lg_delta;
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} else {
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sc->lg_delta_lookup = 0;
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}
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}
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static void
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size_classes(
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/* Output. */
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sc_data_t *sc_data,
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/* Determined by the system. */
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size_t lg_ptr_size, int lg_quantum,
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/* Configuration decisions. */
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int lg_tiny_min, int lg_max_lookup, int lg_page, int lg_ngroup) {
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int ptr_bits = (1 << lg_ptr_size) * 8;
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int ngroup = (1 << lg_ngroup);
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int ntiny = 0;
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int nlbins = 0;
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int lg_tiny_maxclass = (unsigned)-1;
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int nbins = 0;
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int npsizes = 0;
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int index = 0;
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int ndelta = 0;
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int lg_base = lg_tiny_min;
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int lg_delta = lg_base;
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/* Outputs that we update as we go. */
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size_t lookup_maxclass = 0;
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size_t small_maxclass = 0;
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int lg_large_minclass = 0;
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size_t large_maxclass = 0;
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/* Tiny size classes. */
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while (lg_base < lg_quantum) {
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sc_t *sc = &sc_data->sc[index];
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size_class(sc, lg_max_lookup, lg_page, lg_ngroup, index,
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lg_base, lg_delta, ndelta);
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if (sc->lg_delta_lookup != 0) {
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nlbins = index + 1;
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}
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if (sc->psz) {
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npsizes++;
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}
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if (sc->bin) {
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nbins++;
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}
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ntiny++;
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/* Final written value is correct. */
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lg_tiny_maxclass = lg_base;
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index++;
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lg_delta = lg_base;
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lg_base++;
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}
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/* First non-tiny (pseudo) group. */
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if (ntiny != 0) {
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sc_t *sc = &sc_data->sc[index];
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/*
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* See the note in sc.h; the first non-tiny size class has an
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* unusual encoding.
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*/
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lg_base--;
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ndelta = 1;
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size_class(sc, lg_max_lookup, lg_page, lg_ngroup, index,
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lg_base, lg_delta, ndelta);
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index++;
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lg_base++;
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lg_delta++;
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if (sc->psz) {
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npsizes++;
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}
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if (sc->bin) {
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nbins++;
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}
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}
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while (ndelta < ngroup) {
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sc_t *sc = &sc_data->sc[index];
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size_class(sc, lg_max_lookup, lg_page, lg_ngroup, index,
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lg_base, lg_delta, ndelta);
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index++;
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ndelta++;
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if (sc->psz) {
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npsizes++;
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}
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if (sc->bin) {
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nbins++;
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}
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}
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/* All remaining groups. */
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lg_base = lg_base + lg_ngroup;
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while (lg_base < ptr_bits - 1) {
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ndelta = 1;
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int ndelta_limit;
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if (lg_base == ptr_bits - 2) {
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ndelta_limit = ngroup - 1;
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} else {
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ndelta_limit = ngroup;
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}
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while (ndelta <= ndelta_limit) {
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sc_t *sc = &sc_data->sc[index];
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size_class(sc, lg_max_lookup, lg_page, lg_ngroup, index,
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lg_base, lg_delta, ndelta);
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if (sc->lg_delta_lookup != 0) {
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nlbins = index + 1;
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/* Final written value is correct. */
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lookup_maxclass = (ZU(1) << lg_base)
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+ (ZU(ndelta) << lg_delta);
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}
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if (sc->psz) {
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npsizes++;
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}
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if (sc->bin) {
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nbins++;
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/* Final written value is correct. */
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small_maxclass = (ZU(1) << lg_base)
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+ (ZU(ndelta) << lg_delta);
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if (lg_ngroup > 0) {
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lg_large_minclass = lg_base + 1;
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} else {
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lg_large_minclass = lg_base + 2;
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}
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}
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large_maxclass = (ZU(1) << lg_base)
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+ (ZU(ndelta) << lg_delta);
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index++;
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ndelta++;
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}
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lg_base++;
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lg_delta++;
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}
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/* Additional outputs. */
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int nsizes = index;
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unsigned lg_ceil_nsizes = lg_ceil(nsizes);
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/* Fill in the output data. */
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sc_data->ntiny = ntiny;
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sc_data->nlbins = nlbins;
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sc_data->nbins = nbins;
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sc_data->nsizes = nsizes;
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sc_data->lg_ceil_nsizes = lg_ceil_nsizes;
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sc_data->npsizes = npsizes;
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sc_data->lg_tiny_maxclass = lg_tiny_maxclass;
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sc_data->lookup_maxclass = lookup_maxclass;
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sc_data->small_maxclass = small_maxclass;
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sc_data->lg_large_minclass = lg_large_minclass;
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sc_data->large_minclass = (ZU(1) << lg_large_minclass);
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sc_data->large_maxclass = large_maxclass;
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}
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/*
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* Defined later (after size_classes.h becomes visible), but called during
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* initialization.
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*/
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static void sc_data_assert(sc_data_t *sc_data);
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void
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sc_data_init(sc_data_t *data) {
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assert(SC_NTINY == NTBINS);
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assert(SC_NSIZES == NSIZES);
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assert(SC_NBINS == NBINS);
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assert(NPSIZES <= SC_NPSIZES_MAX);
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assert(!data->initialized);
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data->initialized = true;
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data->ntiny = NTBINS;
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data->nlbins = NLBINS;
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data->nbins = NBINS;
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data->nsizes = NSIZES;
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data->lg_ceil_nsizes = LG_CEIL_NSIZES;
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data->npsizes = NPSIZES;
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#if SC_NTINY != 0
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data->lg_tiny_maxclass = LG_TINY_MAXCLASS;
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#else
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data->lg_tiny_maxclass = -1;
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#endif
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data->lookup_maxclass = LOOKUP_MAXCLASS;
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data->small_maxclass = SMALL_MAXCLASS;
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data->lg_large_minclass = LG_LARGE_MINCLASS;
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data->large_minclass = LARGE_MINCLASS;
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data->large_maxclass = LARGE_MAXCLASS;
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#define no 0
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#define yes 1
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#define SC(index, lg_base_base, lg_delta, ndelta, psz, bin, pgs, \
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lg_delta_lookup) \
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fill_sc(data, index, lg_base_base, lg_delta, ndelta, psz, bin, \
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pgs, lg_delta_lookup);
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SIZE_CLASSES
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#undef no
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#undef yes
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#undef SC
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sc_data_init(sc_data_t *sc_data) {
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assert(!sc_data->initialized);
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int lg_max_lookup = 12;
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size_classes(sc_data, LG_SIZEOF_PTR, LG_QUANTUM, SC_LG_TINY_MIN,
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lg_max_lookup, LG_PAGE, 2);
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sc_data->initialized = true;
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sc_data_assert(sc_data);
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}
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void
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sc_boot() {
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sc_data_init(&sc_data_global);
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}
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/*
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* We don't include size_classes.h until this point, to ensure only the asserts
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* can see it.
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*/
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#include "jemalloc/internal/size_classes.h"
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static void
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sc_assert(sc_t *sc, int index, int lg_base, int lg_delta, int ndelta, int psz,
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int bin, int pgs, int lg_delta_lookup) {
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assert(sc->index == index);
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assert(sc->lg_base == lg_base);
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assert(sc->lg_delta == lg_delta);
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assert(sc->ndelta == ndelta);
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assert(sc->psz == psz);
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assert(sc->bin == bin);
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assert(sc->pgs == pgs);
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assert(sc->lg_delta_lookup == lg_delta_lookup);
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}
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static void
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sc_data_assert(sc_data_t *sc_data) {
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assert(SC_NTINY == NTBINS);
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assert(SC_NSIZES == NSIZES);
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assert(SC_NBINS == NBINS);
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assert(NPSIZES <= SC_NPSIZES_MAX);
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assert(sc_data->ntiny == NTBINS);
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assert(sc_data->nlbins == NLBINS);
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assert(sc_data->nbins == NBINS);
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assert(sc_data->nsizes == NSIZES);
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assert(sc_data->lg_ceil_nsizes == LG_CEIL_NSIZES);
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assert(sc_data->npsizes == NPSIZES);
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#if NTBINS > 0
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assert(sc_data->lg_tiny_maxclass == LG_TINY_MAXCLASS);
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#else
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assert(sc_data->lg_tiny_maxclass == -1);
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#endif
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assert(sc_data->lookup_maxclass == LOOKUP_MAXCLASS);
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assert(sc_data->small_maxclass == SMALL_MAXCLASS);
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assert(sc_data->lg_large_minclass == LG_LARGE_MINCLASS);
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assert(sc_data->large_minclass == LARGE_MINCLASS);
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assert(sc_data->large_maxclass == LARGE_MAXCLASS);
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assert(sc_data->initialized);
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#define no 0
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#define yes 1
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#define SC(index, lg_base, lg_delta, ndelta, psz, bin, pgs, \
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lg_delta_lookup) \
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sc_assert(&sc_data->sc[index], index, lg_base, lg_delta, \
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ndelta, psz, bin, pgs, lg_delta_lookup);
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SIZE_CLASSES
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#undef no
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#undef yes
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#undef SC
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}
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