Implement opt.cache_oblivious.

Keep config.cache_oblivious for now to remain backward-compatible.

INSTALL.md

@@ -185,13 +185,13 @@ any of the following arguments (not a definitive list) to 'configure':
 
 * `--disable-cache-oblivious`
 
-    Disable cache-oblivious large allocation alignment for large allocation
+    Disable cache-oblivious large allocation alignment by default, for large
-    requests with no alignment constraints.  If this feature is disabled, all
+    allocation requests with no alignment constraints.  If this feature is
-    large allocations are page-aligned as an implementation artifact, which can
+    disabled, all large allocations are page-aligned as an implementation
-    severely harm CPU cache utilization.  However, the cache-oblivious layout
+    artifact, which can severely harm CPU cache utilization.  However, the
-    comes at the cost of one extra page per large allocation, which in the
+    cache-oblivious layout comes at the cost of one extra page per large
-    most extreme case increases physical memory usage for the 16 KiB size class
+    allocation, which in the most extreme case increases physical memory usage
-    to 20 KiB.
+    for the 16 KiB size class to 20 KiB.
 
 * `--disable-syscall`
 

doc/jemalloc.xml.in

@@ -936,6 +936,22 @@ mallctl("arena." STRINGIFY(MALLCTL_ARENAS_ALL) ".decay",
         </para></listitem>
       </varlistentry>
 
+      <varlistentry id="opt.cache_oblivious">
+        <term>
+          <mallctl>opt.cache_oblivious</mallctl>
+          (<type>bool</type>)
+          <literal>r-</literal>
+        </term>
+        <listitem><para>Enable / Disable cache-oblivious large allocation
+        alignment, for large requests with no alignment constraints.  If this
+        feature is disabled, all large allocations are page-aligned as an
+        implementation artifact, which can severely harm CPU cache utilization.
+        However, the cache-oblivious layout comes at the cost of one extra page
+        per large allocation, which in the most extreme case increases physical
+        memory usage for the 16 KiB size class to 20 KiB. This option is enabled
+        by default.</para></listitem>
+      </varlistentry>
+
       <varlistentry id="opt.metadata_thp">
         <term>
           <mallctl>opt.metadata_thp</mallctl>

include/jemalloc/internal/jemalloc_internal_externs.h

@@ -33,6 +33,7 @@ extern zero_realloc_action_t opt_zero_realloc_action;
 extern malloc_init_t malloc_init_state;
 extern const char *zero_realloc_mode_names[];
 extern atomic_zu_t zero_realloc_count;
+extern bool opt_cache_oblivious;
 
 /* Number of CPUs. */
 extern unsigned ncpus;

include/jemalloc/internal/prof_inlines.h

@@ -223,7 +223,7 @@ prof_sample_align(size_t orig_align) {
 	 * w/o metadata lookup.
 	 */
 	assert(opt_prof);
-	return (config_cache_oblivious && orig_align < PAGE) ? PAGE :
+	return (opt_cache_oblivious && orig_align < PAGE) ? PAGE :
 	    orig_align;
 }
 

include/jemalloc/internal/sz.h

@@ -45,15 +45,13 @@ extern size_t sz_index2size_tab[SC_NSIZES];
  */
 extern uint8_t sz_size2index_tab[];
 
-static const size_t sz_large_pad =
+/*
-#ifdef JEMALLOC_CACHE_OBLIVIOUS
+ * Padding for large allocations: PAGE when opt_cache_oblivious == true (to
-    PAGE
+ * enable cache index randomization); 0 otherwise.
-#else
+ */
-    0
+extern size_t sz_large_pad;
-#endif
-    ;
 
-extern void sz_boot(const sc_data_t *sc_data);
+extern void sz_boot(const sc_data_t *sc_data, bool cache_oblivious);
 
 JEMALLOC_ALWAYS_INLINE pszind_t
 sz_psz2ind(size_t psz) {

src/ctl.c

@@ -90,6 +90,7 @@ CTL_PROTO(config_utrace)
 CTL_PROTO(config_xmalloc)
 CTL_PROTO(opt_abort)
 CTL_PROTO(opt_abort_conf)
+CTL_PROTO(opt_cache_oblivious)
 CTL_PROTO(opt_trust_madvise)
 CTL_PROTO(opt_confirm_conf)
 CTL_PROTO(opt_hpa)
@@ -395,6 +396,7 @@ static const ctl_named_node_t	config_node[] = {
 static const ctl_named_node_t opt_node[] = {
 	{NAME("abort"),		CTL(opt_abort)},
 	{NAME("abort_conf"),	CTL(opt_abort_conf)},
+	{NAME("cache_oblivious"),	CTL(opt_cache_oblivious)},
 	{NAME("trust_madvise"),	CTL(opt_trust_madvise)},
 	{NAME("confirm_conf"),	CTL(opt_confirm_conf)},
 	{NAME("hpa"),		CTL(opt_hpa)},
@@ -2095,6 +2097,7 @@ CTL_RO_CONFIG_GEN(config_xmalloc, bool)
 
 CTL_RO_NL_GEN(opt_abort, opt_abort, bool)
 CTL_RO_NL_GEN(opt_abort_conf, opt_abort_conf, bool)
+CTL_RO_NL_GEN(opt_cache_oblivious, opt_cache_oblivious, bool)
 CTL_RO_NL_GEN(opt_trust_madvise, opt_trust_madvise, bool)
 CTL_RO_NL_GEN(opt_confirm_conf, opt_confirm_conf, bool)
 CTL_RO_NL_GEN(opt_hpa, opt_hpa, bool)

src/jemalloc.c

@@ -102,6 +102,14 @@ bool	opt_trust_madvise =
 #endif
     ;
 
+bool opt_cache_oblivious =
+#ifdef JEMALLOC_CACHE_OBLIVIOUS
+    true
+#else
+    false
+#endif
+    ;
+
 zero_realloc_action_t opt_zero_realloc_action =
     zero_realloc_action_strict;
 
@@ -1697,7 +1705,7 @@ malloc_init_hard_a0_locked() {
 		prof_boot0();
 	}
 	malloc_conf_init(&sc_data, bin_shard_sizes);
-	sz_boot(&sc_data);
+	sz_boot(&sc_data, opt_cache_oblivious);
 	bin_info_boot(&sc_data, bin_shard_sizes);
 
 	if (opt_stats_print) {
@@ -2790,12 +2798,7 @@ isfree(tsd_t *tsd, void *ptr, size_t usize, tcache_t *tcache, bool slow_path) {
 			 * usize can be trusted to determine szind and slab.
 			 */
 			alloc_ctx.szind = sz_size2index(usize);
-			if (config_cache_oblivious) {
 			alloc_ctx.slab = (alloc_ctx.szind < SC_NBINS);
-			} else {
-				/* Non page aligned must be slab allocated. */
-				alloc_ctx.slab = true;
-			}
 		} else if (opt_prof) {
 			emap_alloc_ctx_lookup(tsd_tsdn(tsd), &arena_emap_global,
 			    ptr, &alloc_ctx);

src/large.c

@@ -95,7 +95,8 @@ large_ralloc_no_move_expand(tsdn_t *tsdn, edata_t *edata, size_t usize,
 	}
 
 	if (zero) {
-		if (config_cache_oblivious) {
+		if (opt_cache_oblivious) {
+			assert(sz_large_pad == PAGE);
 			/*
 			 * Zero the trailing bytes of the original allocation's
 			 * last page, since they are in an indeterminate state.

src/stats.c

@@ -1458,6 +1458,7 @@ stats_general_print(emitter_t *emitter) {
 
 	OPT_WRITE_BOOL("abort")
 	OPT_WRITE_BOOL("abort_conf")
+	OPT_WRITE_BOOL("cache_oblivious")
 	OPT_WRITE_BOOL("confirm_conf")
 	OPT_WRITE_BOOL("retain")
 	OPT_WRITE_CHAR_P("dss")

src/sz.c

@@ -1,9 +1,10 @@
 #include "jemalloc/internal/jemalloc_preamble.h"
+#include "jemalloc/internal/jemalloc_internal_includes.h"
 #include "jemalloc/internal/sz.h"
 
 JEMALLOC_ALIGNED(CACHELINE)
 size_t sz_pind2sz_tab[SC_NPSIZES+1];
-
+size_t sz_large_pad;
 
 size_t
 sz_psz_quantize_floor(size_t size) {
@@ -105,7 +106,8 @@ sz_boot_size2index_tab(const sc_data_t *sc_data) {
 }
 
 void
-sz_boot(const sc_data_t *sc_data) {
+sz_boot(const sc_data_t *sc_data, bool cache_oblivious) {
+	sz_large_pad = cache_oblivious ? PAGE : 0;
 	sz_boot_pind2sz_tab(sc_data);
 	sz_boot_index2size_tab(sc_data);
 	sz_boot_size2index_tab(sc_data);

test/unit/extent_quantize.c

@@ -47,7 +47,7 @@ TEST_BEGIN(test_large_extent_size) {
 	 */
 
 	sz = sizeof(bool);
-	expect_d_eq(mallctl("config.cache_oblivious", (void *)&cache_oblivious,
+	expect_d_eq(mallctl("opt.cache_oblivious", (void *)&cache_oblivious,
 	    &sz, NULL, 0), 0, "Unexpected mallctl failure");
 
 	sz = sizeof(unsigned);

test/unit/mallctl.c

@@ -279,6 +279,7 @@ TEST_BEGIN(test_mallctl_opt) {
 
 	TEST_MALLCTL_OPT(bool, abort, always);
 	TEST_MALLCTL_OPT(bool, abort_conf, always);
+	TEST_MALLCTL_OPT(bool, cache_oblivious, always);
 	TEST_MALLCTL_OPT(bool, trust_madvise, always);
 	TEST_MALLCTL_OPT(bool, confirm_conf, always);
 	TEST_MALLCTL_OPT(const char *, metadata_thp, always);