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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>
This commit is contained in:
Rasmus Villemoes 2016-03-22 20:32:05 +01:00 committed by Martin K. Petersen
parent 9d99a2e33a
commit e1f0bce3a0
2 changed files with 23 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
drivers/scsi/Kconfig
View File

@ -202,12 +202,12 @@ config SCSI_ENCLOSURE
certain enclosure conditions to be reported and is not required.
config SCSI_CONSTANTS
bool "Verbose SCSI error reporting (kernel size +=75K)"
bool "Verbose SCSI error reporting (kernel size += 36K)"
depends on SCSI
help
The error messages regarding your SCSI hardware will be easier to
understand if you say Y here; it will enlarge your kernel by about
75 KB. If in doubt, say Y.
36 KB. If in doubt, say Y.
config SCSI_LOGGING
bool "SCSI logging facility"

26
drivers/scsi/constants.c
View File

@ -292,17 +292,30 @@ bool scsi_opcode_sa_name(int opcode, int service_action,
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 @@ scsi_extd_sense_format(unsigned char asc, unsigned char ascq, const char **fmt)
{
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 &&