From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 17F42C4360C for ; Fri, 27 Sep 2019 15:26:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DE5E4217D7 for ; Fri, 27 Sep 2019 15:26:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727842AbfI0P0o (ORCPT ); Fri, 27 Sep 2019 11:26:44 -0400 Received: from mx2.suse.de ([195.135.220.15]:38580 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727319AbfI0P0o (ORCPT ); Fri, 27 Sep 2019 11:26:44 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 3D241AB7D; Fri, 27 Sep 2019 15:26:42 +0000 (UTC) Message-ID: <471732f03049a1528df1d144013d723041f0a419.camel@suse.de> Subject: Re: [PATCH] scsi: core: Log SCSI command age with errors From: Martin Wilck To: "Milan P. Gandhi" , linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org Cc: jejb@linux.ibm.com, martin.petersen@oracle.com Date: Fri, 27 Sep 2019 17:26:46 +0200 In-Reply-To: <20190923060122.GA9603@machine1> References: <20190923060122.GA9603@machine1> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.32.4 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2019-09-23 at 11:31 +0530, Milan P. Gandhi wrote: > Couple of users had requested to print the SCSI command age along > with command failure errors. This is a small change, but allows > users to get more important information about the command that was > failed, it would help the users in debugging the command failures: > > Signed-off-by: Milan P. Gandhi > --- > diff --git a/drivers/scsi/scsi_logging.c > b/drivers/scsi/scsi_logging.c > index ecc5918e372a..ca2182bc53c6 100644 > --- a/drivers/scsi/scsi_logging.c > +++ b/drivers/scsi/scsi_logging.c > @@ -437,6 +437,7 @@ void scsi_print_result(const struct scsi_cmnd > *cmd, const char *msg, > const char *mlret_string = scsi_mlreturn_string(disposition); > const char *hb_string = scsi_hostbyte_string(cmd->result); > const char *db_string = scsi_driverbyte_string(cmd->result); > + unsigned long cmd_age = (jiffies - cmd->jiffies_at_alloc) / HZ; This comes down to pretty coarse time resolution, does it not? More often than not, the time difference shown will be 0. I'd recommend at least millisecond resolution. > > logbuf = scsi_log_reserve_buffer(&logbuf_len); > if (!logbuf) > @@ -478,10 +479,15 @@ void scsi_print_result(const struct scsi_cmnd > *cmd, const char *msg, > > if (db_string) > off += scnprintf(logbuf + off, logbuf_len - off, > - "driverbyte=%s", db_string); > + "driverbyte=%s ", db_string); > else > off += scnprintf(logbuf + off, logbuf_len - off, > - "driverbyte=0x%02x", driver_byte(cmd- > >result)); > + "driverbyte=0x%02x ", > + driver_byte(cmd->result)); > + > + off += scnprintf(logbuf + off, logbuf_len - off, > + "cmd-age=%lus", cmd_age); This is certainly helpful in some situations. Yet I am unsure if it should *always* be printed. I wouldn't say it's as important as the other stuff scsi_print_result() provides. After all, by activating MLQUEUE+MLCOMPLETE, the time on-wire can be extracted with better accuracy from currently available logs. So perhaps make this depend on a module parameter? Also, we should carefully ponder if we want to put this on the same line as the driver byte, as users may have created scripts for parsing this output. Regards, Martin