added new command line option heap_size_hint for greedy GC

NEWS.md

@@ -32,6 +32,9 @@ Command-line option changes
 * `--math-mode=fast` is now a no-op ([#41638]). Users are encouraged to use the @fastmath macro instead, which has more well-defined semantics.
 * The `--threads` command-line option now accepts `auto|N[,auto|M]` where `M` specifies the
   number of interactive threads to create (`auto` currently means 1) ([#42302]).
+* New option `--heap-size-hint=<size>` gives a memory hint for triggering greedy garbage
+  collection. The size might be specified in bytes, kilobytes(1000k), megabytes(300M),
+  gigabytes(1.5G)
 
 Multi-threading changes
 -----------------------

base/options.jl

@@ -52,6 +52,7 @@ struct JLOptions
     rr_detach::Int8
     strip_metadata::Int8
     strip_ir::Int8
+    heap_size_hint::UInt64
 end
 
 # This runs early in the sysimage != is not defined yet

doc/man/julia.1

@@ -216,6 +216,11 @@ expressions. It first tries to use BugReporting.jl installed in current environm
 fallbacks to the latest compatible BugReporting.jl if not. For more information, see
 --bug-report=help.
 
+.TP
+--heap-size-hint=<size>
+Forces garbage collection if memory usage is higher that value. The memory hint might be
+specified in megabytes (500M) or gigabytes (1.5G)
+
 .TP
 --compile={yes*|no|all|min}
 Enable or disable JIT compiler, or request exhaustive or minimal compilation

src/gc.c

@@ -589,17 +589,19 @@ static int64_t last_gc_total_bytes = 0;
 // max_total_memory is a suggestion.  We try very hard to stay
 // under this limit, but we will go above it rather than halting.
 #ifdef _P64
+typedef uint64_t memsize_t;
 #define default_collect_interval (5600*1024*sizeof(void*))
 static size_t max_collect_interval = 1250000000UL;
 // Eventually we can expose this to the user/ci.
-static uint64_t max_total_memory = (uint64_t) 2 * 1024 * 1024 * 1024 * 1024 * 1024;
+memsize_t max_total_memory = (memsize_t) 2 * 1024 * 1024 * 1024 * 1024 * 1024;
 #else
+typedef uint32_t memsize_t;
 #define default_collect_interval (3200*1024*sizeof(void*))
 static size_t max_collect_interval =  500000000UL;
 // Work really hard to stay within 2GB
 // Alternative is to risk running out of address space
 // on 32 bit architectures.
-static uint32_t max_total_memory = (uint32_t) 2 * 1024 * 1024 * 1024;
+memsize_t max_total_memory = (memsize_t) 2 * 1024 * 1024 * 1024;
 #endif
 
 // global variables for GC stats
@@ -3446,6 +3448,13 @@ void jl_gc_init(void)
     t_start = jl_hrtime();
 }
 
+void jl_gc_set_max_memory(uint64_t max_mem) {
+    if (max_mem > 0
+        && max_mem < (uint64_t)1 << (sizeof(memsize_t) * 8 - 1)) {
+        max_total_memory = max_mem;
+    }
+}
+
 // callback for passing OOM errors from gmp
 JL_DLLEXPORT void jl_throw_out_of_memory_error(void)
 {

src/jloptions.c

@@ -85,6 +85,7 @@ JL_DLLEXPORT void jl_init_options(void)
                         0, // rr-detach
                         0, // strip-metadata
                         0, // strip-ir
+                        0, // heap-size-hint
     };
     jl_options_initialized = 1;
 }
@@ -177,6 +178,9 @@ static const char opts[]  =
     "                            expressions. It first tries to use BugReporting.jl installed in current environment and\n"
     "                            fallbacks to the latest compatible BugReporting.jl if not. For more information, see\n"
     "                            --bug-report=help.\n\n"
+
+    " --heap-size-hint=<size>    Forces garbage collection if memory usage is higher that value.\n"
+    "                            The memory hint might be specified in megabytes(500M) or gigabytes(1G)\n\n"
 ;
 
 static const char opts_hidden[]  =
@@ -242,6 +246,7 @@ JL_DLLEXPORT void jl_parse_opts(int *argcp, char ***argvp)
            opt_rr_detach,
            opt_strip_metadata,
            opt_strip_ir,
+           opt_heap_size_hint,
     };
     static const char* const shortopts = "+vhqH:e:E:L:J:C:it:p:O:g:";
     static const struct option longopts[] = {
@@ -297,6 +302,7 @@ JL_DLLEXPORT void jl_parse_opts(int *argcp, char ***argvp)
         { "rr-detach",       no_argument,       0, opt_rr_detach },
         { "strip-metadata",  no_argument,       0, opt_strip_metadata },
         { "strip-ir",        no_argument,       0, opt_strip_ir },
+        { "heap-size-hint",  required_argument, 0, opt_heap_size_hint },
         { 0, 0, 0, 0 }
     };
 
@@ -755,6 +761,42 @@ JL_DLLEXPORT void jl_parse_opts(int *argcp, char ***argvp)
             break;
         case opt_strip_ir:
             jl_options.strip_ir = 1;
+            break;
+        case opt_heap_size_hint:
+            if (optarg != NULL) {
+                size_t endof = strlen(optarg);
+                long double value = 0.0;
+                if (sscanf(optarg, "%Lf", &value) == 1 && value > 1e-7) {
+                    char unit = optarg[endof - 1];
+                    uint64_t multiplier = 1ull;
+                    switch (unit) {
+                        case 'k':
+                        case 'K':
+                            multiplier <<= 10;
+                            break;
+                        case 'm':
+                        case 'M':
+                            multiplier <<= 20;
+                            break;
+                        case 'g':
+                        case 'G':
+                            multiplier <<= 30;
+                            break;
+                        case 't':
+                        case 'T':
+                            multiplier <<= 40;
+                            break;
+                        default:
+                            break;
+                    }
+                    jl_options.heap_size_hint = (uint64_t)(value * multiplier);
+
+                    jl_gc_set_max_memory(jl_options.heap_size_hint);
+                }
+            }
+            if (jl_options.heap_size_hint == 0)
+                jl_errorf("julia: invalid argument to --heap-size-hint without memory size specified");
+
             break;
         default:
             jl_errorf("julia: unhandled option -- %c\n"

src/jloptions.h

@@ -56,6 +56,7 @@ typedef struct {
     int8_t rr_detach;
     int8_t strip_metadata;
     int8_t strip_ir;
+    uint64_t heap_size_hint;
 } jl_options_t;
 
 #endif

src/julia_internal.h

@@ -467,6 +467,9 @@ void jl_gc_count_allocd(size_t sz) JL_NOTSAFEPOINT;
 void jl_gc_run_all_finalizers(jl_task_t *ct);
 void jl_release_task_stack(jl_ptls_t ptls, jl_task_t *task);
 
+// Set GC memory trigger in bytes for greedy memory collecting
+void jl_gc_set_max_memory(uint64_t max_mem);
+
 JL_DLLEXPORT void jl_gc_queue_binding(jl_binding_t *bnd) JL_NOTSAFEPOINT;
 void gc_setmark_buf(jl_ptls_t ptls, void *buf, uint8_t, size_t) JL_NOTSAFEPOINT;