Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7AE0AC4332F for ; Mon, 13 Dec 2021 10:03:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240799AbhLMKCl (ORCPT ); Mon, 13 Dec 2021 05:02:41 -0500 Received: from ams.source.kernel.org ([145.40.68.75]:39308 "EHLO ams.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239382AbhLMJ5P (ORCPT ); Mon, 13 Dec 2021 04:57:15 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 416B1B80E63; Mon, 13 Dec 2021 09:57:14 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3C112C34601; Mon, 13 Dec 2021 09:57:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1639389433; bh=BtnyKAUcFEHFJBGJih+sKxOT3PrmwV4N42S+2eNTadY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=vTa2BGlZtRCzkyz2h2MDQWNIn22WgnEwrPhizMmrB5GfMIfvuyOeB4kSEU4Uf0isz rbb7LLS/k7uxhEkZIyGUmfgyngdm5IzlRXD3x4JSV2traWR+oaHUsKBFw/Y8ZH6ucs O/Pzcs6PXk/Y4OXJGaGUrP6KYe91rB+9iJZvApNs= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Oleksandr Natalenko , SeongJae Park , John Stultz , Thomas Gleixner , Andrew Morton , Linus Torvalds Subject: [PATCH 5.15 061/171] mm/damon/core: fix fake load reports due to uninterruptible sleeps Date: Mon, 13 Dec 2021 10:29:36 +0100 Message-Id: <20211213092947.137050575@linuxfoundation.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20211213092945.091487407@linuxfoundation.org> References: <20211213092945.091487407@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: SeongJae Park commit 70e9274805fccfd175d0431a947bfd11ee7df40e upstream. Because DAMON sleeps in uninterruptible mode, /proc/loadavg reports fake load while DAMON is turned on, though it is doing nothing. This can confuse users[1]. To avoid the case, this commit makes DAMON sleeps in idle mode. [1] https://lore.kernel.org/all/11868371.O9o76ZdvQC@natalenko.name/ Link: https://lkml.kernel.org/r/20211126145015.15862-3-sj@kernel.org Fixes: 2224d8485492 ("mm: introduce Data Access MONitor (DAMON)") Reported-by: Oleksandr Natalenko Signed-off-by: SeongJae Park Tested-by: Oleksandr Natalenko Cc: John Stultz Cc: Thomas Gleixner Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/damon/core.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -357,6 +357,15 @@ int damon_start(struct damon_ctx **ctxs, return err; } +static void kdamond_usleep(unsigned long usecs) +{ + /* See Documentation/timers/timers-howto.rst for the thresholds */ + if (usecs > 20 * 1000) + schedule_timeout_idle(usecs_to_jiffies(usecs)); + else + usleep_idle_range(usecs, usecs + 1); +} + /* * __damon_stop() - Stops monitoring of given context. * @ctx: monitoring context @@ -370,8 +379,7 @@ static int __damon_stop(struct damon_ctx ctx->kdamond_stop = true; mutex_unlock(&ctx->kdamond_lock); while (damon_kdamond_running(ctx)) - usleep_range(ctx->sample_interval, - ctx->sample_interval * 2); + kdamond_usleep(ctx->sample_interval); return 0; } mutex_unlock(&ctx->kdamond_lock); @@ -670,7 +678,7 @@ static int kdamond_fn(void *data) ctx->callback.after_sampling(ctx)) set_kdamond_stop(ctx); - usleep_range(ctx->sample_interval, ctx->sample_interval + 1); + kdamond_usleep(ctx->sample_interval); if (ctx->primitive.check_accesses) max_nr_accesses = ctx->primitive.check_accesses(ctx);