Modify maxram to mean the most we'll allocate in one chunk and add usable_ram for the most we'll allocate to one task.

Limit all maxram on 32bits to 1GB since most don't like mallocing more than this.
Update testing to allow larger total amount based on usable ram while sticking to maxram limit per alloc.

lrzip_private.h

@@ -213,6 +213,7 @@ struct rzip_control {
 	const char *suffix;
 	int compression_level;
 	i64 overhead; // compressor overhead
+	i64 usable_ram; // the most ram we'll try to use on one activity
 	i64 maxram; // the largest chunk of ram to allocate
 	unsigned char lzma_properties[5]; // lzma properties, encoded
 	i64 window;

main.c

@@ -766,16 +766,15 @@ int main(int argc, char *argv[])
 		else
 			control.maxram = control.ramsize / 3;
 		if (BITS32) {
-			i64 usable_ram;
-
 			/* Decrease usable ram size on 32 bits due to kernel /
 			 * userspace split. Cannot allocate larger than a 1
 			 * gigabyte chunk due to 32 bit signed long being
 			 * used in alloc */
-			usable_ram = MAX(control.ramsize - 900000000ll, 900000000ll);
+			control.usable_ram = MAX(control.ramsize - 900000000ll, 900000000ll);
-			control.maxram = MIN(control.maxram, usable_ram);
+			control.maxram = MIN(control.maxram, control.usable_ram);
 			control.maxram = MIN(control.maxram, one_g);
-		}
+		} else
+			control.usable_ram = control.maxram;
 		round_to_page(&control.maxram);
 
 		show_summary();

rzip.c

@@ -812,11 +812,6 @@ void rzip_fd(rzip_control *control, int fd_in, int fd_out)
 	 * buffer to work on 2/3 ram size, leaving enough ram for the
 	 * compression backends */
 	control->max_mmap = control->maxram;
-
-	/* On 32 bits we can have a big window with sliding mmap, but can
-	 * not enable much per mmap/malloc */
-	if (BITS32)
-		control->max_mmap = MIN((unsigned long long)control->max_mmap, two_gig);
 	round_to_page(&control->max_mmap);
 
 	/* Set maximum chunk size to 2/3 of ram if not unlimited or specified

stream.c

@@ -985,14 +985,9 @@ void *open_stream_out(rzip_control *control, int f, unsigned int n, i64 chunk_li
 	else
 		testbufs = 2;
 
-	/* Serious limits imposed on 32 bit capabilities */
-	if (BITS32)
-		limit = MIN((unsigned long long)limit, (two_gig / testbufs) -
-			(control->overhead * control->threads));
-
 	testsize = (limit * testbufs) + (control->overhead * control->threads);
-	if (testsize > control->maxram)
+	if (testsize > control->usable_ram)
-		limit = (control->maxram - (control->overhead * control->threads)) / testbufs;
+		limit = (control->usable_ram - (control->overhead * control->threads)) / testbufs;
 
 	/* If we don't have enough ram for the number of threads, decrease the
 	 * number of threads till we do, or only have one thread. */
@@ -1001,17 +996,30 @@ void *open_stream_out(rzip_control *control, int f, unsigned int n, i64 chunk_li
 			--control->threads;
 		else
 			break;
-		limit = (control->maxram - (control->overhead * control->threads)) / testbufs;
+		limit = (control->usable_ram - (control->overhead * control->threads)) / testbufs;
 		limit = MIN(limit, chunk_limit);
 	}
+	if (BITS32) // Shouldn't be higher than this by now, but just in case
+		limit = MIN(limit, one_g);
+	/* Use a nominal minimum size should we fail all previous shrinking */
 	limit = MAX(limit, STREAM_BUFSIZE);
 retest_malloc:
-	testsize = (limit * testbufs) + (control->overhead * control->threads);
+	testsize = limit + (control->overhead * control->threads);
 	testmalloc = malloc(testsize);
 	if (!testmalloc) {
 		limit = limit / 10 * 9;
 		goto retest_malloc;
 	}
+	if (!NO_COMPRESS) {
+		char *testmalloc2 = malloc(limit);
+
+		if (!testmalloc2) {
+			free(testmalloc);
+			limit = limit / 10 * 9;
+			goto retest_malloc;
+		}
+		free(testmalloc2);
+	}
 	free(testmalloc);
 	print_maxverbose("Succeeded in testing %lld sized malloc for back end compression\n", testsize);