scsi: reduce CONFIG_SCSI_CONSTANTS=y impact by 8k
On 64 bit, struct error_info has 6 bytes of padding, which amounts to
over 4k of wasted space in the additional[] array. We could easily get
rid of that by instead using separate arrays for the codes and the
pointers. However, we can do even better than that and save an
additional 6 bytes per entry: In the table, just store the sizeof()
the corresponding string literal. The cumulative sum of these is then
the appropriate offset into additional_text, which is built from the
concatenation (with '\0's inbetween) of the strings.
$ scripts/bloat-o-meter /tmp/vmlinux vmlinux
add/remove: 0/0 grow/shrink: 1/1 up/down: 24/-8488 (-8464)
function old new delta
scsi_extd_sense_format 136 160 +24
additional 11312 2824 -8488
The Kconfig help text used to say that CONFIG_SCSI_CONSTANTS=y costs
around 75 KB, but that was a little exaggerated. The actual number was
closer to 44K, and 36K with this patch.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Tested-by: Douglas Gilbert <dgilbert@interlog.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
diff --git a/drivers/scsi/constants.c b/drivers/scsi/constants.c
index 6e813ee..83458f7 100644
--- a/drivers/scsi/constants.c
+++ b/drivers/scsi/constants.c
@@ -292,17 +292,30 @@
struct error_info {
unsigned short code12; /* 0x0302 looks better than 0x03,0x02 */
- const char * text;
+ unsigned short size;
};
+/*
+ * There are 700+ entries in this table. To save space, we don't store
+ * (code, pointer) pairs, which would make sizeof(struct
+ * error_info)==16 on 64 bits. Rather, the second element just stores
+ * the size (including \0) of the corresponding string, and we use the
+ * sum of these to get the appropriate offset into additional_text
+ * defined below. This approach saves 12 bytes per entry.
+ */
static const struct error_info additional[] =
{
-#define SENSE_CODE(c, s) {c, s},
+#define SENSE_CODE(c, s) {c, sizeof(s)},
#include "sense_codes.h"
#undef SENSE_CODE
- {0, NULL}
};
+static const char *additional_text =
+#define SENSE_CODE(c, s) s "\0"
+#include "sense_codes.h"
+#undef SENSE_CODE
+ ;
+
struct error_info2 {
unsigned char code1, code2_min, code2_max;
const char * str;
@@ -364,11 +377,14 @@
{
int i;
unsigned short code = ((asc << 8) | ascq);
+ unsigned offset = 0;
*fmt = NULL;
- for (i = 0; additional[i].text; i++)
+ for (i = 0; i < ARRAY_SIZE(additional); i++) {
if (additional[i].code12 == code)
- return additional[i].text;
+ return additional_text + offset;
+ offset += additional[i].size;
+ }
for (i = 0; additional2[i].fmt; i++) {
if (additional2[i].code1 == asc &&
ascq >= additional2[i].code2_min &&