mksquashfs: add a new -mem <mbytes> option

Add a new -mem <mbytes> option, that sets the amount of memory
Mksquashfs uses to <mbytes>.  Internally, the <mbytes> is distributed
amongst the four caches: reader cache, fragment cache, block writer cache,
and fragment writer cache in an optimal ratio, as is already done
when deciding how to allocate the default physical memory amongst the
caches.

This option is intended to be much more understandable than the
previous -read-queue, -fragment-queue and -write-queue options, such
that people might actually use this option (whereas it is clear
nobody used the previous options, as they were evidently too difficult
to understand).

Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>

1 files changed, 33 insertions, 18 deletions

diff --git a/squashfs-tools/mksquashfs.c b/squashfs-tools/mksquashfs.c
index a38ed19..3f9baab 100644
--- a/squashfs-tools/mksquashfs.c
+++ b/squashfs-tools/mksquashfs.c
@@ -4840,31 +4840,29 @@ int get_physical_memory()
 
 	long long num_pages = sysconf(_SC_PHYS_PAGES);
 	long long page_size = sysconf(_SC_PAGESIZE);
-
-	return num_pages * page_size >> 20;
-}
-
-
-void calculate_queue_sizes(int *readq, int *fragq, int *bwriteq, int *fwriteq)
-{
-	int phys_mem = get_physical_memory();
+	int phys_mem = num_pages * page_size >> 20;
 
 	if(phys_mem < SQUASHFS_LOWMEM)
 		BAD_ERROR("Mksquashfs requires more physical memory than is "
 			"available!\n");
 
 	/* Only take 1/SQUASHFS_TAKE of physical memory */
-	phys_mem /= SQUASHFS_TAKE;
+	return phys_mem / SQUASHFS_TAKE;
+}
 
-	*readq = phys_mem / SQUASHFS_READQ_MEM;
-	*bwriteq = phys_mem / SQUASHFS_BWRITEQ_MEM;
-	*fwriteq = phys_mem / SQUASHFS_FWRITEQ_MEM;
-	*fragq = phys_mem - *readq - *bwriteq - *fwriteq;
+
+void calculate_queue_sizes(int mem, int *readq, int *fragq, int *bwriteq,
+							int *fwriteq)
+{
+	*readq = mem / SQUASHFS_READQ_MEM;
+	*bwriteq = mem / SQUASHFS_BWRITEQ_MEM;
+	*fwriteq = mem / SQUASHFS_FWRITEQ_MEM;
+	*fragq = mem - *readq - *bwriteq - *fwriteq;
 }
 
 
 #define VERSION() \
-	printf("mksquashfs version 4.2-git (2014/04/20)\n");\
+	printf("mksquashfs version 4.2-git (2014/04/23)\n");\
 	printf("copyright (C) 2014 Phillip Lougher "\
 		"<phillip@squashfs.org.uk>\n\n"); \
 	printf("This program is free software; you can redistribute it and/or"\
@@ -4892,6 +4890,7 @@ int main(int argc, char *argv[])
 	int fragq;
 	int bwriteq;
 	int fwriteq;
+	int total_mem = get_physical_memory();
 	int progress = TRUE;
 	int force_progress = FALSE;
 	struct file_buffer **fragment = NULL;
@@ -4902,7 +4901,7 @@ int main(int argc, char *argv[])
 	}
 
 	block_log = slog(block_size);
-	calculate_queue_sizes(&readq, &fragq, &bwriteq, &fwriteq);
+	calculate_queue_sizes(total_mem, &readq, &fragq, &bwriteq, &fwriteq);
 
         for(i = 1; i < argc && argv[i][0] != '-'; i++);
 	if(i < 3)
@@ -5095,6 +5094,19 @@ print_compressor_options:
 					"megabyte or larger\n", argv[0]);
 				exit(1);
 			}
+		} else if(strcmp(argv[i], "-mem") == 0) {
+			if((++i == argc) || !parse_num(argv[i], &total_mem)) {
+				ERROR("%s: -mem missing or invalid mem size\n",
+					 argv[0]);
+				exit(1);
+			}
+			if(total_mem < SQUASHFS_LOWMEM) {
+				ERROR("%s: -mem should be %d Mbytes or "
+					"larger\n", SQUASHFS_LOWMEM, argv[0]);
+				exit(1);
+			}
+			calculate_queue_sizes(total_mem, &readq, &fragq,
+				&bwriteq, &fwriteq);
 		} else if(strcmp(argv[i], "-b") == 0) {
 			if(++i == argc) {
 				ERROR("%s: -b missing block size\n", argv[0]);
@@ -5311,13 +5323,16 @@ printOptions:
 			ERROR("-processors <number>\tUse <number> processors."
 				"  By default will use number of\n");
 			ERROR("\t\t\tprocessors available\n");
+			ERROR("-mem <size>\t\tUse <size> Mbytes.  Currently "
+				"set to %d Mbytes\n", total_mem);
 			ERROR("-read-queue <size>\tSet input queue to <size> "
-				"Mbytes.  Default %d Mbytes\n", readq);
+				"Mbytes.  Currently set to %d Mbytes\n", readq);
 			ERROR("-write-queue <size>\tSet output queue to <size> "
-				"Mbytes.  Default %d Mbytes\n",
+				"Mbytes.  Currently set to %d Mbytes\n",
 				bwriteq + fwriteq);
 			ERROR("-fragment-queue <size>\tSet fragment queue to "
-				"<size> Mbytes.  Default %d Mbytes\n", fragq);
+				"<size> Mbytes.  Currently set to %d Mbytes\n",
+				fragq);
 			ERROR("\nMiscellaneous options:\n");
 			ERROR("-root-owned\t\talternative name for -all-root"
 				"\n");