| Message ID | 1448358147-23663-4-git-send-email-linux@rasmusvillemoes.dk (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
On 15-11-24 04:42 AM, Rasmus Villemoes wrote: > 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 > > Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Tested-by: Douglas Gilbert <dgilbert@interlog.com> > --- > drivers/scsi/constants.c | 26 +++++++++++++++++++++----- > 1 file changed, 21 insertions(+), 5 deletions(-) > > 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 && > -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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 &&
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 Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> --- drivers/scsi/constants.c | 26 +++++++++++++++++++++----- 1 file changed, 21 insertions(+), 5 deletions(-)