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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable 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 9D811C433EF for ; Mon, 9 Sep 2019 10:24:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 741BA2089F for ; Mon, 9 Sep 2019 10:24:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=arista.com header.i=@arista.com header.b="XMwbu7B5" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390812AbfIIKYY (ORCPT ); Mon, 9 Sep 2019 06:24:24 -0400 Received: from mail-wm1-f68.google.com ([209.85.128.68]:39835 "EHLO mail-wm1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390597AbfIIKXt (ORCPT ); Mon, 9 Sep 2019 06:23:49 -0400 Received: by mail-wm1-f68.google.com with SMTP id q12so13994093wmj.4 for ; Mon, 09 Sep 2019 03:23:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=arista.com; s=googlenew; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=STLctuURefaE8eq55GBboHVj7+QXpVRUnAJsIE8QlMY=; b=XMwbu7B5OAgAIWw6N2LtryeCTvQ6z3+05hNQ741oPpGzrgd7tXuAkkU5zdc3X/eqlD yiG4Gmi4sTjgvThu5RQsAALJWUCRUekt+KXZnGUx3ELzgvvgcr2QaY/r7DGaasyT2tDw 5qTGdnitBh3WFpeDyGDVP8LHsDpqHI+/GRyiiFZq0Li1sjubvjRX5RiioqxW1bJiEnXH Uy0OVpQKqUjqjQ31Me19gCjqn13KYbhrB1YPo2wHuo24N28g+cKTvYI7Zc1vvUGsAWmu QF1hzkYFCwmTBiO9omikKuQXD539nG96dOaFw4+JkHg//ePtrRAiF98KfEWUyoFnOKaG KmLQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=STLctuURefaE8eq55GBboHVj7+QXpVRUnAJsIE8QlMY=; b=fP3JCmgwXxunDjvlubbnJ9kCbcQC1IvMWQJmePHloymGXVlQOr3QY6C3mH2zZHSTfN lB+6Cby8a0lXUgk8HLrKh8LJ6wzz9pDbb5QzOOQanAJzuOHDx97GyvPCI6NxqEmPCPC5 AcSBG2/4VDfNRhgYqsvLdREjPHVUrGK3Y2vPwkYPhnKifqPjB+wdkRjlFhSDAGocoybG koNqHfIZ83ecl4kxzhxPdJe+EjjFYiFbTz4vW216PelH0hMa5caq0Ml5jH90SlFmx4mA bfPyuX00rRfOvNQP1E8rQtiz39ZwLuZNphwcJiAO6e0Awd3D2On7uwqtuEQFSYRtXKgy tUaw== X-Gm-Message-State: APjAAAXohVens11n4jafNkvT0xqu5+tPCSOKrNXagq7IqOJPv9qTBOyI S/2cD2Dw4DVTLLeLf/F+Ing6SA== X-Google-Smtp-Source: APXvYqwlnYxK/Ion+EpCVZ4VcHAZvyCrtmY/DDiUgd2oheMGu7g2FrmmWJ0F4QyACrXJgUyTC44ndA== X-Received: by 2002:a7b:c651:: with SMTP id q17mr17777639wmk.13.1568024627727; Mon, 09 Sep 2019 03:23:47 -0700 (PDT) Received: from Mindolluin.localdomain ([148.69.85.38]) by smtp.gmail.com with ESMTPSA id d14sm1800008wrj.27.2019.09.09.03.23.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 09 Sep 2019 03:23:47 -0700 (PDT) From: Dmitry Safonov To: linux-kernel@vger.kernel.org Cc: Dmitry Safonov <0x7f454c46@gmail.com>, Dmitry Safonov , Adrian Reber , Alexander Viro , Andrei Vagin , Andy Lutomirski , Cyrill Gorcunov , Ingo Molnar , Oleg Nesterov , Pavel Emelyanov , Thomas Gleixner , containers@lists.linux-foundation.org, linux-fsdevel@vger.kernel.org Subject: [PATCH 3/9] select: Convert __esimate_accuracy() to ktime_t Date: Mon, 9 Sep 2019 11:23:34 +0100 Message-Id: <20190909102340.8592-4-dima@arista.com> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20190909102340.8592-1-dima@arista.com> References: <20190909102340.8592-1-dima@arista.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org __estimate_accuracy() divides 64-bit integers twice which is suboptimal. Converting to ktime_t not only avoids that, but also simplifies the logic on some extent. The long-term goal is to convert poll() to leave timeout value in ktime_t inside restart_block as it's the only user that leaves it in timespec. That's a preparation ground for introducing a new ptrace() request that will dump timeout for interrupted syscall. Furthermore, do_select() and do_poll() actually both need time in ktime_t for poll_schedule_timeout(), so there is this hack that converts time on the first loop. It's not only a "hack", but also it's done every time poll() syscall is restarted. After conversion it'll be removed. While at it, rename parameters "slack" and "timeout" which describe their purpose better. Signed-off-by: Dmitry Safonov --- fs/select.c | 33 +++++++++++++-------------------- 1 file changed, 13 insertions(+), 20 deletions(-) diff --git a/fs/select.c b/fs/select.c index 53a0c149f528..12cdefd3be2d 100644 --- a/fs/select.c +++ b/fs/select.c @@ -36,7 +36,7 @@ /* - * Estimate expected accuracy in ns from a timeval. + * Estimate expected accuracy in ns. * * After quite a bit of churning around, we've settled on * a simple thing of taking 0.1% of the timeout as the @@ -49,22 +49,17 @@ #define MAX_SLACK (100 * NSEC_PER_MSEC) -static long __estimate_accuracy(struct timespec64 *tv) +static long __estimate_accuracy(ktime_t slack) { - long slack; int divfactor = 1000; - if (tv->tv_sec < 0) + if (slack < 0) return 0; if (task_nice(current) > 0) divfactor = divfactor / 5; - if (tv->tv_sec > MAX_SLACK / (NSEC_PER_SEC/divfactor)) - return MAX_SLACK; - - slack = tv->tv_nsec / divfactor; - slack += tv->tv_sec * (NSEC_PER_SEC/divfactor); + slack = ktime_divns(slack, divfactor); if (slack > MAX_SLACK) return MAX_SLACK; @@ -72,27 +67,25 @@ static long __estimate_accuracy(struct timespec64 *tv) return slack; } -u64 select_estimate_accuracy(struct timespec64 *tv) +u64 select_estimate_accuracy(struct timespec64 *timeout) { - u64 ret; - struct timespec64 now; + ktime_t now, slack; /* * Realtime tasks get a slack of 0 for obvious reasons. */ - if (rt_task(current)) return 0; - ktime_get_ts64(&now); - now = timespec64_sub(*tv, now); - ret = __estimate_accuracy(&now); - if (ret < current->timer_slack_ns) - return current->timer_slack_ns; - return ret; -} + now = ktime_get(); + slack = now - timespec64_to_ktime(*timeout); + slack = __estimate_accuracy(slack); + if (slack < current->timer_slack_ns) + return current->timer_slack_ns; + return slack; +} struct poll_table_page { struct poll_table_page * next; -- 2.23.0