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dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.a=rsa-sha256 header.s=2020 header.b=V/ZRW2Sr; dkim=pass header.d=linutronix.de header.i=@linutronix.de header.a=ed25519-sha256 header.s=2020e header.b=WQ+iY6r2 From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1794573739; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=JLUI7FK8wijRXIgsxgkbmCRNaskdZBcmIaMMGBQKBFo=; b=V/ZRW2Sr4yciOmhEqKh2Wr1h5IpHV6FzTfysv3zuhAiKC7kPk1PefBs1o2DQ2YDeODwZj9 aZF/zHRVxSqCYPmd31yVdBQFe5i16+ugTLYUcgE0e/RPoPn8Q9S+yj9PQMMF9+nNDfvDV2 VykiqWfFS4d8YgFJz2SggSaijvj4Kd/FhdZifmEAve+wUGDw2gKlC6VbVCjTJEZ2kAG3om v33l1FW0SAd/yxiasEqtGU/4GJdIK4FIiK1s3qwLqm3Pa56bO+gf/vaxffXIqdQ9GkojZ9 j0JQbNVvozDe42uDins0Kck6bdnL9CQCamk+2kJNmP7D/sttPzrH5Gkcjn9sWw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1794573739; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=JLUI7FK8wijRXIgsxgkbmCRNaskdZBcmIaMMGBQKBFo=; b=WQ+iY6r28A4zagAf1Bp6obxiNpjdBrGY788qf6Sl5OYqe2EAc4atdVr+LEWlWW+PLfudX9 xV6IJg2PAUMEy+Cg== To: Daniel Wagner , Steven Rostedt , Tomas Glozar , Sebastian Andrzej Siewior , Clark Williams Cc: linux-trace-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, Daniel Wagner Subject: Re: [PATCH] rtla/timerlat: Lock the memory of the user-space threads In-Reply-To: <20261112-rtla-mlock-v1-1-418986711b20@monom.org> References: <20261112-rtla-mlock-v1-1-418986711b20@monom.org> Date: Fri, 13 Nov 2026 13:48:18 +0106 Message-ID: <87qzgox5qt.fsf@jogness.linutronix.de> X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain Hi Daniel, On 2026-11-12, Daniel Wagner wrote: > diff --git a/tools/tracing/rtla/src/timerlat_u.c b/tools/tracing/rtla/src/timerlat_u.c > index c80edaf07b00..42aaf1d7f216 100644 > --- a/tools/tracing/rtla/src/timerlat_u.c > +++ b/tools/tracing/rtla/src/timerlat_u.c > @@ -69,6 +70,15 @@ static int timerlat_u_main(int cpu, struct timerlat_u_params *params) > } > } > > + /* > + * Keep the measuring process in memory: the latency it reports > + * runs until it is back in user space, and a page fault on the way > + * (its code, stack or libc pages reclaimed under memory pressure) > + * would count as latency. cyclictest does the same with -m. > + */ > + if (mlockall(MCL_CURRENT | MCL_FUTURE)) > + err_msg("Could not lock timerlat u memory: %s\n", strerror(errno)); > + Page faulting should happen _before_ the task has a real-time priority. Real-time priorities are for real-time workloads. Just move this up 30 lines. John Ogness