From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D6B7F33CFC for ; Wed, 29 May 2024 08:25:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716971144; cv=none; b=T/nnwUSc5EI4Tnpk9N1a33rQzdaMAzaVYGwIJbBhTazviaeWOhuAj+S+lZaJwBJoofAFYtxeKeuCpIzPQH8YamudZ59jZ9SS5EpBKNMTQ1TkQRUYIlklo/PkRoEruwPVdWSuwhW3i9GFdeVnE6I9VIX+yi35JT24t6NE407bioo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716971144; c=relaxed/simple; bh=Z56n3pknVfrdXrYQxZGakMySYcLNvBhOCiTixUpe2BA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=CUEBy/BG/JvPWNjc+j0RRky3JJd6VmYd088Psl82GXHizKKdNJ0Zrl5weJhp+0AkV1GtNwp5fKw1+qoYmSWGphKNPkSNdTg/WEBmkJvctFK4t8noVWGHKSInaMtkpCGEjjBh82KFEUn2Tw0gChDbHkNGVYLD5/n/gEp+DOV+kIY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=QkRXAPMF; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="QkRXAPMF" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=KedQfEOQGeFOWrHJKw+wmkld2KwmplKUWUwSLw2frR0=; b=QkRXAPMFWCH8tpmeWVx5ll+tyl Y7tOijGOQF2hr5zB0I4JweymOLwa2cTwa93rixzwb73HGFf6ZnX/rZ0uQyaiZmhvNobGE2HWkKfrH Zw8uCOT91n9lnOPmZDNZLm4VCS/RL8h9q694IxKviy0OaUyKTai8m0K8yvUhlPT6BMC3E7utmPatr BxBZYbME8/yQ+fV/BymLX16fFuGsbrtuCp2LMffeirC+p+Men7pYAHgb8JSnr+F89YEnXzPhJVEWE wWkud4Fau1Ud4kQz/SSN/c2W395KONMY7LAcnNP7U0EJdHb9iXc3y1XAVwWy1dtj01kZ8qh+lFJq3 XBS1G5ow==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.97.1 #2 (Red Hat Linux)) id 1sCEcm-0000000DT4e-3wsZ; Wed, 29 May 2024 08:25:33 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 238E930073F; Wed, 29 May 2024 10:25:30 +0200 (CEST) Date: Wed, 29 May 2024 10:25:30 +0200 From: Peter Zijlstra To: Ankur Arora Cc: linux-kernel@vger.kernel.org, tglx@linutronix.de, torvalds@linux-foundation.org, paulmck@kernel.org, rostedt@goodmis.org, mark.rutland@arm.com, juri.lelli@redhat.com, joel@joelfernandes.org, raghavendra.kt@amd.com, sshegde@linux.ibm.com, boris.ostrovsky@oracle.com, konrad.wilk@oracle.com, Ingo Molnar , Vincent Guittot Subject: Re: [PATCH v2 07/35] sched: define *_tsk_need_resched_lazy() helpers Message-ID: <20240529082530.GJ26599@noisy.programming.kicks-ass.net> References: <20240528003521.979836-1-ankur.a.arora@oracle.com> <20240528003521.979836-8-ankur.a.arora@oracle.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240528003521.979836-8-ankur.a.arora@oracle.com> On Mon, May 27, 2024 at 05:34:53PM -0700, Ankur Arora wrote: > static inline void clear_tsk_need_resched(struct task_struct *tsk) > { > - clear_tsk_thread_flag(tsk,TIF_NEED_RESCHED); > + clear_tsk_thread_flag(tsk, tif_resched(RESCHED_NOW)); > + > + if (IS_ENABLED(CONFIG_PREEMPT_AUTO)) > + clear_tsk_thread_flag(tsk, tif_resched(RESCHED_LAZY)); > +} (using tif_resched() here is really uncalled for) So this will generate rather sub-optimal code, namely 2 atomics that really should be one. Ideally we'd write this something like: unsigned long mask = _TIF_NEED_RESCHED; if (IS_ENABLED(CONFIG_PREEMPT_AUTO)) mask |= _TIF_NEED_RESCHED_LAZY; atomic_long_andnot(mask, (atomic_long_t *)task_thread_info(tsk)->flags); Which will clear both bits with a single atomic.