From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757478AbcKCO0a (ORCPT ); Thu, 3 Nov 2016 10:26:30 -0400 Received: from mail-cys01nam02on0063.outbound.protection.outlook.com ([104.47.37.63]:56786 "EHLO NAM02-CY1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754749AbcKCO03 (ORCPT ); Thu, 3 Nov 2016 10:26:29 -0400 Authentication-Results: spf=none (sender IP is ) smtp.mailfrom=Bart.VanAssche@sandisk.com; Subject: Re: [PATCH 1/4] block: add scalable completion tracking of requests To: Jens Axboe , , , References: <1478034325-28232-1-git-send-email-axboe@fb.com> <1478034325-28232-2-git-send-email-axboe@fb.com> CC: From: Bart Van Assche Message-ID: <12323199-84d1-7586-9189-3bf5644248a0@sandisk.com> Date: Thu, 3 Nov 2016 08:10:16 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: <1478034325-28232-2-git-send-email-axboe@fb.com> Content-Type: text/plain; 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> +} > + > +static bool __blk_stat_is_current(struct blk_rq_stat *stat, s64 now) > +{ > + return (now & BLK_STAT_NSEC_MASK) == (stat->time & BLK_STAT_NSEC_MASK); > +} > + > +bool blk_stat_is_current(struct blk_rq_stat *stat) > +{ > + return __blk_stat_is_current(stat, ktime_to_ns(ktime_get())); > +} Hello Jens, What is the performance impact of these patches? My experience is that introducing ktime_get() in the I/O path of high-performance I/O devices measurably slows down I/O. On https://lkml.org/lkml/2016/4/21/107 I read that a single ktime_get() call takes about 100 ns. Bart.