From patchwork Tue Mar 27 19:05:33 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Douglas Gilbert X-Patchwork-Id: 10311513 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id CA09B60212 for ; Tue, 27 Mar 2018 19:05:50 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id BC190288DA for ; Tue, 27 Mar 2018 19:05:50 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id B0A3129C91; Tue, 27 Mar 2018 19:05:50 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 50C47288DA for ; Tue, 27 Mar 2018 19:05:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751127AbeC0TFs (ORCPT ); Tue, 27 Mar 2018 15:05:48 -0400 Received: from smtp.infotech.no ([82.134.31.41]:44518 "EHLO smtp.infotech.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751075AbeC0TFr (ORCPT ); Tue, 27 Mar 2018 15:05:47 -0400 Received: from localhost (localhost [127.0.0.1]) by smtp.infotech.no (Postfix) with ESMTP id E0F682041AC; Tue, 27 Mar 2018 21:05:45 +0200 (CEST) X-Virus-Scanned: by amavisd-new-2.6.6 (20110518) (Debian) at infotech.no Received: from smtp.infotech.no ([127.0.0.1]) by localhost (smtp.infotech.no [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id JNJC7vrQcHAY; Tue, 27 Mar 2018 21:05:45 +0200 (CEST) Received: from xtwo70.bingwo.ca (host-184-164-15-239.dyn.295.ca [184.164.15.239]) by smtp.infotech.no (Postfix) with ESMTPA id AB83F204154; Tue, 27 Mar 2018 21:05:44 +0200 (CEST) From: Douglas Gilbert To: linux-scsi@vger.kernel.org Cc: martin.petersen@oracle.com, jejb@linux.vnet.ibm.com, hare@suse.de, bart.vanassche@wdc.com, jthumshirn@suse.de Subject: [PATCH v3 6/7] scsi_io_completion hints on fastpatch Date: Tue, 27 Mar 2018 15:05:33 -0400 Message-Id: <20180327190534.10449-7-dgilbert@interlog.com> X-Mailer: git-send-email 2.14.1 In-Reply-To: <20180327190534.10449-1-dgilbert@interlog.com> References: <20180327190534.10449-1-dgilbert@interlog.com> Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Add likely() and unlikely() hints to conditionals on or near the fastpath. Signed-off-by: Douglas Gilbert Reviewed-by: Johannes Thumshirn --- A reviewer wanted any performance improvement (or otherwise) quantified. The improvement was so small, that ftrace ignored it. Inline timing code suggests the improvement from this whole patchset is around 7 nanoseconds per invocation (tested on a Lenovo X270 (i5-7200U)). Not exactly huge. Another win might be the smaller size of scsi_io_completion() after the refactoring; this should allow more other code to fit in the instruction cache. drivers/scsi/scsi_lib.c | 22 ++++++++++------------ 1 file changed, 10 insertions(+), 12 deletions(-) diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index e7e5eb5b9e2e..391bbb0b19b8 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -1028,17 +1028,17 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes) struct request *req = cmd->request; blk_status_t blk_stat = BLK_STS_OK; - if (result) /* does not necessarily mean there is an error */ + if (unlikely(result)) /* a nz result may or may not be an error */ result = scsi_io_completion_nz_result(cmd, result, &blk_stat); - if (blk_rq_is_passthrough(req)) { + if (unlikely(blk_rq_is_passthrough(req))) { /* * __scsi_error_from_host_byte may have reset the host_byte */ scsi_req(req)->result = cmd->result; scsi_req(req)->resid_len = scsi_get_resid(cmd); - if (scsi_bidi_cmnd(cmd)) { + if (unlikely(scsi_bidi_cmnd(cmd))) { /* * Bidi commands Must be complete as a whole, * both sides at once. @@ -1051,7 +1051,7 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes) } } - /* no bidi support for !blk_rq_is_passthrough yet */ + /* no bidi support yet, other than in pass-through */ BUG_ON(blk_bidi_rq(req)); /* @@ -1067,15 +1067,13 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes) * handle. Failed, zero length commands always need to drop down * to retry code. Fast path should return in this block. */ - if (blk_rq_bytes(req) > 0 || blk_stat == BLK_STS_OK) { - if (!scsi_end_request(req, blk_stat, good_bytes, 0)) - return; /* no bytes remaining */ + if (likely(blk_rq_bytes(req) > 0 || blk_stat == BLK_STS_OK)) { + if (likely(!scsi_end_request(req, blk_stat, good_bytes, 0))) + return; /* no bytes remaining */ } - /* - * Kill remainder if no retrys. - */ - if (blk_stat && scsi_noretry_cmd(cmd)) { + /* Kill remainder if no retries */ + if (unlikely(blk_stat && scsi_noretry_cmd(cmd))) { if (scsi_end_request(req, blk_stat, blk_rq_bytes(req), 0)) BUG(); return; @@ -1085,7 +1083,7 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes) * If there had been no error, but we have leftover bytes in the * requeues just queue the command up again. */ - if (result == 0) + if (likely(result == 0)) scsi_io_completion_reprep(cmd, q); else scsi_io_completion_action(cmd, result);