From e1f0bce3a0db95007fec756225801e50477f32fd Mon Sep 17 00:00:00 2001 From: Rasmus Villemoes Date: Tue, 22 Mar 2016 20:32:05 +0100 Subject: 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 Reviewed-by: Hannes Reinecke Tested-by: Douglas Gilbert Reviewed-by: Christoph Hellwig Signed-off-by: Martin K. Petersen --- drivers/scsi/constants.c | 26 +++++++++++++++++++++----- 1 file changed, 21 insertions(+), 5 deletions(-) (limited to 'drivers/scsi/constants.c') diff --git a/drivers/scsi/constants.c b/drivers/scsi/constants.c index 6e813eec4f8d..83458f7a2824 100644 --- a/drivers/scsi/constants.c +++ b/drivers/scsi/constants.c @@ -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 && -- cgit