From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754041AbbKXJn1 (ORCPT ); Tue, 24 Nov 2015 04:43:27 -0500 Received: from mail-lf0-f46.google.com ([209.85.215.46]:33537 "EHLO mail-lf0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753690AbbKXJmu (ORCPT ); Tue, 24 Nov 2015 04:42:50 -0500 From: Rasmus Villemoes To: Christoph Hellwig , Hannes Reinecke , Bart Van Assche , "James E.J. Bottomley" , Julian Calaby Cc: Rasmus Villemoes , linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 3/3] scsi: reduce CONFIG_SCSI_CONSTANTS=y impact by 8k Date: Tue, 24 Nov 2015 10:42:27 +0100 Message-Id: <1448358147-23663-4-git-send-email-linux@rasmusvillemoes.dk> X-Mailer: git-send-email 2.6.1 In-Reply-To: <1448358147-23663-1-git-send-email-linux@rasmusvillemoes.dk> References: <1448358147-23663-1-git-send-email-linux@rasmusvillemoes.dk> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- 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 && -- 2.6.1