Commit e1f0bce3 authored by Rasmus Villemoes's avatar Rasmus Villemoes Committed by Martin K. Petersen
Browse files

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: default avatarRasmus Villemoes <linux@rasmusvillemoes.dk>
Reviewed-by: default avatarHannes Reinecke <hare@suse.com>
Tested-by: default avatarDouglas Gilbert <dgilbert@interlog.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
parent 9d99a2e3

drivers/scsi/Kconfig

+2 −2
Original line number Diff line number Diff line
@@ -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"

drivers/scsi/constants.c

+21 −5
Original line number Diff line number Diff line
@@ -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 &&

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