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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4E80FC433EF for ; Wed, 24 Nov 2021 14:52:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1348599AbhKXOzh (ORCPT ); Wed, 24 Nov 2021 09:55:37 -0500 Received: from mail.kernel.org ([198.145.29.99]:53292 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344961AbhKXOzg (ORCPT ); Wed, 24 Nov 2021 09:55:36 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 6990D60524; Wed, 24 Nov 2021 14:52:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1637765547; bh=5dhCOHOPDLaykpUjwDvndyMO8fDWAczCxAEVkK7Z7WM=; h=From:To:Cc:Subject:Date:From; b=pxZMCdE36FKsG3OKrHfqS8gJ/XQb+zDkgcjWs1LT1CwIW6boCLsAc62ocselrpKPc do1tVWsaG4Fm5fpODLW3v0sz1ovCTL9oSrw0M211Nd5u0FDuAFQ/EG6lu5/9bTKcLQ hcL5k+GW46zEtP7RRGxygNDt+KWrCqkcuW4y9GzagvtATa5m/TfiKuY1jL0tS9P0Lg xuCLDg6JqNaeLjtgx/nZ2sn8KZFLdcgN0vGmLa333f2d886diok6nCi9bfS7PabdnA LKdtZ6gTTkzXkJvIP8bTPeCwJlJW7ZSqg+4xyE9CDrFnIdHx+Eddut/ZnTqXQmz+B0 Qo3k1AQcPC+UQ== From: SeongJae Park To: akpm@linux-foundation.org Cc: shakeelb@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, SeongJae Park , stable@vger.kernel.org Subject: [PATCH] mm/damon/core: Avoid fake load reports due to uninterruptible sleeps Date: Wed, 24 Nov 2021 14:52:19 +0000 Message-Id: <20211124145219.32866-1-sj@kernel.org> X-Mailer: git-send-email 2.17.1 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org 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/ Fixes: 2224d8485492 ("mm: introduce Data Access MONitor (DAMON)") Reported-by: Oleksandr Natalenko Signed-off-by: SeongJae Park Cc: # 5.15.x --- I think this needs to be applied on v5.15.y, but this cannot cleanly applied there as is. I will back-port this on v5.15.y and post later once this is merged in the mainline. mm/damon/core.c | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-) diff --git a/mm/damon/core.c b/mm/damon/core.c index daacd9536c7c..7813f47aadc9 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -12,6 +12,8 @@ #include #include #include +#include +#include #include #include @@ -976,12 +978,25 @@ static unsigned long damos_wmark_wait_us(struct damos *scheme) return 0; } +/* sleep for @usecs in idle mode */ +static void __sched damon_usleep_idle(unsigned long usecs) +{ + ktime_t exp = ktime_add_us(ktime_get(), usecs); + u64 delta = usecs * NSEC_PER_USEC / 100; /* allow 1% error */ + + for (;;) { + __set_current_state(TASK_IDLE); + if (!schedule_hrtimeout_range(&exp, delta, HRTIMER_MODE_ABS)) + break; + } +} + static void kdamond_usleep(unsigned long usecs) { if (usecs > 100 * 1000) - schedule_timeout_interruptible(usecs_to_jiffies(usecs)); + schedule_timeout_idle(usecs_to_jiffies(usecs)); else - usleep_range(usecs, usecs + 1); + damon_usleep_idle(usecs); } /* Returns negative error code if it's not activated but should return */ @@ -1036,7 +1051,7 @@ static int kdamond_fn(void *data) ctx->callback.after_sampling(ctx)) done = true; - 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); -- 2.17.1