Make 8-byte tiny size class non-optional.
When tiny size class support was first added, it was intended to support truly tiny size classes (even 2 bytes). However, this wasn't very useful in practice, so the minimum tiny size class has been limited to sizeof(void *) for a long time now. This is too small to be standards compliant, but other commonly used malloc implementations do not even bother using a 16-byte quantum on systems with vector units (SSE2+, AltiVEC, etc.). As such, it is safe in practice to support an 8-byte tiny size class on 64-bit systems that support 16-byte types.
This commit is contained in:
Jason Evans
101
src/arena.c
101
src/arena.c
@@ -28,14 +28,7 @@ size_t mspace_mask;
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* const_small_size2bin is a static constant lookup table that in the common
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* case can be used as-is for small_size2bin.
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*/
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#if (LG_TINY_MIN == 2)
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#define S2B_4(i) i,
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#define S2B_8(i) S2B_4(i) S2B_4(i)
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#elif (LG_TINY_MIN == 3)
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#define S2B_8(i) i,
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#else
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# error "Unsupported LG_TINY_MIN"
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#endif
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#define S2B_16(i) S2B_8(i) S2B_8(i)
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#define S2B_32(i) S2B_16(i) S2B_16(i)
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#define S2B_64(i) S2B_32(i) S2B_32(i)
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@@ -49,23 +42,9 @@ static JEMALLOC_ATTR(aligned(CACHELINE))
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const uint8_t const_small_size2bin[] = {
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#if (LG_QUANTUM == 4)
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/* 16-byte quantum **********************/
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# ifdef JEMALLOC_TINY
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# if (LG_TINY_MIN == 2)
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S2B_4(0) /* 4 */
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S2B_4(1) /* 8 */
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S2B_8(2) /* 16 */
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# define S2B_QMIN 2
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# elif (LG_TINY_MIN == 3)
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S2B_8(0) /* 8 */
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S2B_8(1) /* 16 */
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# define S2B_QMIN 1
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# else
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# error "Unsupported LG_TINY_MIN"
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# endif
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# else
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S2B_16(0) /* 16 */
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# define S2B_QMIN 0
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# endif
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S2B_8(0) /* 8 */
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S2B_8(1) /* 16 */
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# define S2B_QMIN 1
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S2B_16(S2B_QMIN + 1) /* 32 */
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S2B_16(S2B_QMIN + 2) /* 48 */
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S2B_16(S2B_QMIN + 3) /* 64 */
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@@ -76,18 +55,8 @@ static JEMALLOC_ATTR(aligned(CACHELINE))
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# define S2B_CMIN (S2B_QMIN + 8)
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#else
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/* 8-byte quantum ***********************/
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# ifdef JEMALLOC_TINY
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# if (LG_TINY_MIN == 2)
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S2B_4(0) /* 4 */
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S2B_4(1) /* 8 */
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# define S2B_QMIN 1
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# else
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# error "Unsupported LG_TINY_MIN"
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# endif
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# else
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S2B_8(0) /* 8 */
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# define S2B_QMIN 0
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# endif
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# define S2B_QMIN 0
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S2B_8(S2B_QMIN + 0) /* 8 */
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S2B_8(S2B_QMIN + 1) /* 16 */
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S2B_8(S2B_QMIN + 2) /* 24 */
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S2B_8(S2B_QMIN + 3) /* 32 */
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@@ -2153,17 +2122,15 @@ small_size2bin_validate(void)
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i = 1;
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/* Tiny. */
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if (config_tiny) {
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for (; i < (1U << LG_TINY_MIN); i++) {
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size = pow2_ceil(1U << LG_TINY_MIN);
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binind = ffs((int)(size >> (LG_TINY_MIN + 1)));
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assert(SMALL_SIZE2BIN(i) == binind);
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}
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for (; i < qspace_min; i++) {
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size = pow2_ceil(i);
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binind = ffs((int)(size >> (LG_TINY_MIN + 1)));
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assert(SMALL_SIZE2BIN(i) == binind);
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}
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for (; i < TINY_MIN; i++) {
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size = TINY_MIN;
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binind = ffs((int)(size >> (LG_TINY_MIN + 1)));
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assert(SMALL_SIZE2BIN(i) == binind);
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}
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for (; i < qspace_min; i++) {
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size = pow2_ceil(i);
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binind = ffs((int)(size >> (LG_TINY_MIN + 1)));
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assert(SMALL_SIZE2BIN(i) == binind);
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}
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/* Quantum-spaced. */
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for (; i <= qspace_max; i++) {
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@@ -2223,17 +2190,15 @@ small_size2bin_init_hard(void)
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i = 1;
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/* Tiny. */
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if (config_tiny) {
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for (; i < (1U << LG_TINY_MIN); i += TINY_MIN) {
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size = pow2_ceil(1U << LG_TINY_MIN);
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binind = ffs((int)(size >> (LG_TINY_MIN + 1)));
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CUSTOM_SMALL_SIZE2BIN(i) = binind;
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}
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for (; i < qspace_min; i += TINY_MIN) {
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size = pow2_ceil(i);
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binind = ffs((int)(size >> (LG_TINY_MIN + 1)));
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CUSTOM_SMALL_SIZE2BIN(i) = binind;
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}
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for (; i < TINY_MIN; i += TINY_MIN) {
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size = TINY_MIN;
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binind = ffs((int)(size >> (LG_TINY_MIN + 1)));
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CUSTOM_SMALL_SIZE2BIN(i) = binind;
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}
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for (; i < qspace_min; i += TINY_MIN) {
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size = pow2_ceil(i);
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binind = ffs((int)(size >> (LG_TINY_MIN + 1)));
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CUSTOM_SMALL_SIZE2BIN(i) = binind;
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}
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/* Quantum-spaced. */
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for (; i <= qspace_max; i += TINY_MIN) {
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@@ -2398,17 +2363,12 @@ bin_info_init(void)
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prev_run_size = PAGE_SIZE;
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i = 0;
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/* (2^n)-spaced tiny bins. */
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if (config_tiny) {
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for (; i < ntbins; i++) {
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bin_info = &arena_bin_info[i];
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bin_info->reg_size = (1U << (LG_TINY_MIN + i));
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prev_run_size = bin_info_run_size_calc(bin_info,
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prev_run_size);
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bitmap_info_init(&bin_info->bitmap_info,
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bin_info->nregs);
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}
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for (; i < ntbins; i++) {
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bin_info = &arena_bin_info[i];
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bin_info->reg_size = (1U << (LG_TINY_MIN + i));
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prev_run_size = bin_info_run_size_calc(bin_info, prev_run_size);
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bitmap_info_init(&bin_info->bitmap_info, bin_info->nregs);
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}
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/* Quantum-spaced bins. */
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for (; i < ntbins + nqbins; i++) {
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bin_info = &arena_bin_info[i];
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@@ -2416,7 +2376,6 @@ bin_info_init(void)
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prev_run_size = bin_info_run_size_calc(bin_info, prev_run_size);
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bitmap_info_init(&bin_info->bitmap_info, bin_info->nregs);
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}
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/* Cacheline-spaced bins. */
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for (; i < ntbins + nqbins + ncbins; i++) {
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bin_info = &arena_bin_info[i];
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@@ -2425,7 +2384,6 @@ bin_info_init(void)
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prev_run_size = bin_info_run_size_calc(bin_info, prev_run_size);
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bitmap_info_init(&bin_info->bitmap_info, bin_info->nregs);
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}
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/* Subpage-spaced bins. */
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for (; i < nbins; i++) {
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bin_info = &arena_bin_info[i];
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@@ -2456,8 +2414,7 @@ arena_boot(void)
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assert(sspace_min < PAGE_SIZE);
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sspace_max = PAGE_SIZE - SUBPAGE;
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if (config_tiny)
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assert(LG_QUANTUM >= LG_TINY_MIN);
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assert(LG_QUANTUM >= LG_TINY_MIN);
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assert(ntbins <= LG_QUANTUM);
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nqbins = qspace_max >> LG_QUANTUM;
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ncbins = ((cspace_max - cspace_min) >> LG_CACHELINE) + 1;
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@@ -56,7 +56,6 @@ CTL_PROTO(config_prof_libunwind)
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CTL_PROTO(config_stats)
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CTL_PROTO(config_sysv)
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CTL_PROTO(config_tcache)
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CTL_PROTO(config_tiny)
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CTL_PROTO(config_tls)
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CTL_PROTO(config_xmalloc)
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CTL_PROTO(opt_abort)
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@@ -199,7 +198,6 @@ static const ctl_node_t config_node[] = {
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{NAME("stats"), CTL(config_stats)},
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{NAME("sysv"), CTL(config_sysv)},
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{NAME("tcache"), CTL(config_tcache)},
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{NAME("tiny"), CTL(config_tiny)},
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{NAME("tls"), CTL(config_tls)},
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{NAME("xmalloc"), CTL(config_xmalloc)}
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};
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@@ -993,8 +991,6 @@ n##_ctl(const size_t *mib, size_t miblen, void *oldp, size_t *oldlenp, \
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int ret; \
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bool oldval; \
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\
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if (n == false) \
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return (ENOENT); \
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READONLY(); \
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oldval = n; \
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READ(oldval, bool); \
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@@ -1115,7 +1111,6 @@ CTL_RO_BOOL_CONFIG_GEN(config_prof_libunwind)
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CTL_RO_BOOL_CONFIG_GEN(config_stats)
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CTL_RO_BOOL_CONFIG_GEN(config_sysv)
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CTL_RO_BOOL_CONFIG_GEN(config_tcache)
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CTL_RO_BOOL_CONFIG_GEN(config_tiny)
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CTL_RO_BOOL_CONFIG_GEN(config_tls)
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CTL_RO_BOOL_CONFIG_GEN(config_xmalloc)
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@@ -1203,8 +1198,8 @@ CTL_RO_NL_GEN(arenas_cacheline, CACHELINE, size_t)
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CTL_RO_NL_GEN(arenas_subpage, SUBPAGE, size_t)
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CTL_RO_NL_GEN(arenas_pagesize, PAGE_SIZE, size_t)
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CTL_RO_NL_GEN(arenas_chunksize, chunksize, size_t)
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CTL_RO_NL_CGEN(config_tiny, arenas_tspace_min, (1U << LG_TINY_MIN), size_t)
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CTL_RO_NL_CGEN(config_tiny, arenas_tspace_max, (qspace_min >> 1), size_t)
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CTL_RO_NL_GEN(arenas_tspace_min, TINY_MIN, size_t)
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CTL_RO_NL_GEN(arenas_tspace_max, (qspace_min >> 1), size_t)
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CTL_RO_NL_GEN(arenas_qspace_min, qspace_min, size_t)
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CTL_RO_NL_GEN(arenas_qspace_max, qspace_max, size_t)
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CTL_RO_NL_GEN(arenas_cspace_min, cspace_min, size_t)
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