From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752640AbbJEJ1J (ORCPT ); Mon, 5 Oct 2015 05:27:09 -0400 Received: from mail-lb0-f171.google.com ([209.85.217.171]:36019 "EHLO mail-lb0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752570AbbJEJ1A (ORCPT ); Mon, 5 Oct 2015 05:27:00 -0400 From: Rasmus Villemoes To: Christoph Hellwig , Hannes Reinecke , "James E.J. Bottomley" Cc: linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, Rasmus Villemoes Subject: [PATCH 2/2] scsi: reduce CONFIG_SCSI_CONSTANTS=y impact by 8k Date: Mon, 5 Oct 2015 11:26:40 +0200 Message-Id: <1444037200-14684-3-git-send-email-linux@rasmusvillemoes.dk> X-Mailer: git-send-email 2.1.3 In-Reply-To: <1444037200-14684-1-git-send-email-linux@rasmusvillemoes.dk> References: <20151004080217.GA22816@infradead.org> <1444037200-14684-1-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 | 25 +++++++++++++++++++++---- drivers/scsi/sense_codes.h | 2 -- 2 files changed, 21 insertions(+), 6 deletions(-) diff --git a/drivers/scsi/constants.c b/drivers/scsi/constants.c index 47aaccd5e68e..ccd34b0481cd 100644 --- a/drivers/scsi/constants.c +++ b/drivers/scsi/constants.c @@ -292,17 +292,31 @@ 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 }; +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 +378,14 @@ 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 && diff --git a/drivers/scsi/sense_codes.h b/drivers/scsi/sense_codes.h index 54b3939d6309..da84d53b3379 100644 --- a/drivers/scsi/sense_codes.h +++ b/drivers/scsi/sense_codes.h @@ -833,5 +833,3 @@ SENSE_CODE(0x746E, "External data encryption control timeout") SENSE_CODE(0x746F, "External data encryption control error") SENSE_CODE(0x7471, "Logical unit access not authorized") SENSE_CODE(0x7479, "Security conflict in translated device") - -SENSE_CODE(0, NULL) -- 2.1.3