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
parent
0fee70d718
commit
ef8897b4b9
7
INSTALL
7
INSTALL
@ -90,13 +90,6 @@ any of the following arguments (not a definitive list) to 'configure':
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Statically link against the specified libunwind.a rather than dynamically
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linking with -lunwind.
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--disable-tiny
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Disable tiny (sub-quantum-sized) object support. Technically it is not
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legal for a malloc implementation to allocate objects with less than
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quantum alignment (8 or 16 bytes, depending on architecture), but in
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practice it never causes any problems if, for example, 4-byte allocations
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are 4-byte-aligned.
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--disable-tcache
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Disable thread-specific caches for small objects. Objects are cached and
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released in bulk, thus reducing the total number of mutex operations. See
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17
configure.ac
17
configure.ac
@ -560,22 +560,6 @@ if test "x$enable_prof" = "x1" ; then
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fi
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AC_SUBST([enable_prof])
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dnl Enable tiny allocations by default.
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AC_ARG_ENABLE([tiny],
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[AS_HELP_STRING([--disable-tiny], [Disable tiny (sub-quantum) allocations])],
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[if test "x$enable_tiny" = "xno" ; then
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enable_tiny="0"
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else
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enable_tiny="1"
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fi
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],
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[enable_tiny="1"]
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)
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if test "x$enable_tiny" = "x1" ; then
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AC_DEFINE([JEMALLOC_TINY], [ ])
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fi
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AC_SUBST([enable_tiny])
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dnl Enable thread-specific caching by default.
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AC_ARG_ENABLE([tcache],
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[AS_HELP_STRING([--disable-tcache], [Disable per thread caches])],
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@ -934,7 +918,6 @@ AC_MSG_RESULT([prof : ${enable_prof}])
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AC_MSG_RESULT([prof-libunwind : ${enable_prof_libunwind}])
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AC_MSG_RESULT([prof-libgcc : ${enable_prof_libgcc}])
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AC_MSG_RESULT([prof-gcc : ${enable_prof_gcc}])
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AC_MSG_RESULT([tiny : ${enable_tiny}])
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AC_MSG_RESULT([tcache : ${enable_tcache}])
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AC_MSG_RESULT([fill : ${enable_fill}])
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AC_MSG_RESULT([xmalloc : ${enable_xmalloc}])
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@ -455,13 +455,12 @@ for (i = 0; i < nbins; i++) {
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allocations in constant time.</para>
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<para>Small objects are managed in groups by page runs. Each run maintains
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a frontier and free list to track which regions are in use. Unless
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<option>--disable-tiny</option> is specified during configuration,
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allocation requests that are no more than half the quantum (8 or 16,
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depending on architecture) are rounded up to the nearest power of two that
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is at least <code language="C">sizeof(<type>void *</type>)</code>.
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Allocation requests that are more than half the quantum, but no more than
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the minimum cacheline-multiple size class (see the <link
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a frontier and free list to track which regions are in use. Allocation
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requests that are no more than half the quantum (8 or 16, depending on
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architecture) are rounded up to the nearest power of two that is at least
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<code language="C">sizeof(<type>void *</type>)</code>. Allocation requests
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that are more than half the quantum, but no more than the minimum
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cacheline-multiple size class (see the <link
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linkend="opt.lg_qspace_max"><mallctl>opt.lg_qspace_max</mallctl></link>
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option) are rounded up to the nearest multiple of the quantum. Allocation
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requests that are more than the minimum cacheline-multiple size class, but
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@ -680,16 +679,6 @@ for (i = 0; i < nbins; i++) {
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during build configuration.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<mallctl>config.tiny</mallctl>
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(<type>bool</type>)
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<literal>r-</literal>
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</term>
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<listitem><para><option>--disable-tiny</option> was not specified
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during build configuration.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<mallctl>config.tls</mallctl>
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@ -17,7 +17,7 @@
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(((s) + SUBPAGE_MASK) & ~SUBPAGE_MASK)
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/* Smallest size class to support. */
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#define LG_TINY_MIN LG_SIZEOF_PTR
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#define LG_TINY_MIN 3
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#define TINY_MIN (1U << LG_TINY_MIN)
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/*
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@ -418,18 +418,13 @@ extern uint8_t const *small_size2bin;
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extern arena_bin_info_t *arena_bin_info;
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/* Various bin-related settings. */
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#ifdef JEMALLOC_TINY /* Number of (2^n)-spaced tiny bins. */
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# define ntbins ((unsigned)(LG_QUANTUM - LG_TINY_MIN))
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#else
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# define ntbins 0
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#endif
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/* Number of (2^n)-spaced tiny bins. */
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#define ntbins ((unsigned)(LG_QUANTUM - LG_TINY_MIN))
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extern unsigned nqbins; /* Number of quantum-spaced bins. */
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extern unsigned ncbins; /* Number of cacheline-spaced bins. */
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extern unsigned nsbins; /* Number of subpage-spaced bins. */
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extern unsigned nbins;
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#ifdef JEMALLOC_TINY
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# define tspace_max ((size_t)(QUANTUM >> 1))
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#endif
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#define tspace_max ((size_t)(QUANTUM >> 1))
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#define qspace_min QUANTUM
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extern size_t qspace_max;
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extern size_t cspace_min;
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@ -633,18 +628,18 @@ arena_prof_ctx_set(const void *ptr, prof_ctx_t *ctx)
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JEMALLOC_INLINE void *
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arena_malloc(size_t size, bool zero)
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{
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tcache_t *tcache = tcache_get();
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tcache_t *tcache;
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assert(size != 0);
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assert(QUANTUM_CEILING(size) <= arena_maxclass);
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if (size <= small_maxclass) {
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if (tcache != NULL)
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if ((tcache = tcache_get()) != NULL)
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return (tcache_alloc_small(tcache, size, zero));
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else
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return (arena_malloc_small(choose_arena(), size, zero));
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} else {
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if (tcache != NULL && size <= tcache_maxclass)
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if (size <= tcache_maxclass && (tcache = tcache_get()) != NULL)
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return (tcache_alloc_large(tcache, size, zero));
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else
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return (arena_malloc_large(choose_arena(), size, zero));
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@ -118,13 +118,6 @@ static const bool config_tcache =
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false
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#endif
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;
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static const bool config_tiny =
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#ifdef JEMALLOC_TINY
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true
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#else
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false
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#endif
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;
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static const bool config_tls =
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#ifdef JEMALLOC_TLS
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true
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@ -79,12 +79,6 @@
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/* Use gcc intrinsics for profile backtracing if defined. */
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#undef JEMALLOC_PROF_GCC
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/*
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* JEMALLOC_TINY enables support for tiny objects, which are smaller than one
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* quantum.
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*/
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#undef JEMALLOC_TINY
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/*
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* JEMALLOC_TCACHE enables a thread-specific caching layer for small objects.
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* This makes it possible to allocate/deallocate objects without any locking
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57
src/arena.c
57
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_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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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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@ -2153,9 +2122,8 @@ 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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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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@ -2164,7 +2132,6 @@ small_size2bin_validate(void)
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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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}
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/* Quantum-spaced. */
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for (; i <= qspace_max; i++) {
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size = QUANTUM_CEILING(i);
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@ -2223,9 +2190,8 @@ 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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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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@ -2234,7 +2200,6 @@ small_size2bin_init_hard(void)
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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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}
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/* Quantum-spaced. */
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for (; i <= qspace_max; i += TINY_MIN) {
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size = QUANTUM_CEILING(i);
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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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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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}
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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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@ -2456,7 +2414,6 @@ 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(ntbins <= LG_QUANTUM);
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nqbins = qspace_max >> LG_QUANTUM;
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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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