From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 A50803F39E0; Tue, 14 Jul 2026 08:07:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784016465; cv=none; b=n5JNcWqCU5kQP52od+YwT0Edee4/cq1cw2Jy0246JVOfa5fov4MeqNEjtpFI8OAJF9CwfeVVuU6lFuh9MJRGBtn/NRhZ4Kpu5S/xFHackX/1ZVqf2o385hH7ScwsoLa1Zv9H2yEP+s0go2iyBf36uy3sdOIaZ2eAC/MO0IveILU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784016465; c=relaxed/simple; bh=yymu7pX1olpJnZgqTPiyuTAISFaK+DCGp0TLxJXpy40=; h=Date:Message-ID:From:To:Cc:Subject:In-Reply-To:References; b=jcHSZdIKyAnHVQnEvra46cQ3xXrtnZjnMRLxVOGPWFUsg58GM3UW9QK2jzsD5yT79GzFHeyVFNg67wws9nwfQxJRMZG23637+0e2wNYkQ31jyweLfunKRBX89tRx0OmpX1DOCka9iE6t4gROVz0kdEwoUGpm3a0ka+bhnqQbjfo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=B38z0U2Y; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="B38z0U2Y" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 27C741F000E9; Tue, 14 Jul 2026 08:07:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784016464; bh=yymu7pX1olpJnZgqTPiyuTAISFaK+DCGp0TLxJXpy40=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=B38z0U2YqQznd82KM/pwQYnIG0UYBctDO+hS0jUtCdrorRk2wZMR7RL+8s/ewNJe7 IHXAgwP4be/2rKwqC+/R09kNveQZzDeOz66tNz6JB0qdNpDYWgia/Uodzg3+s+gxm+ kn6ABAWSbFW7/9S7pnecVsJ1G3su6tFsJ3hI7ddlEbyxT7RKGyHZgCjiCv7zlMJTZ/ GFKFbLmuR1MUumFgfEFHJxwU3BcHpEKty/UQf5yOum7inaJADn9MnUSRaTWMRrO+iP ytj17XGQvEmFH2I2EF8zm4/KHJqFr34nv1pCQPhW5ADgc0mX9lJt6F+iJSg1jAnalt dJs4ZhlrlJIsA== Date: Mon, 13 Jul 2026 22:07:43 -1000 Message-ID: <8839b71f9320a2fb81be66a2ca84cf86@kernel.org> From: Tejun Heo To: Andrea Righi Cc: David Vernet , Changwoo Min , sched-ext@lists.linux.dev, Emil Tsalapatis , linux-kernel@vger.kernel.org Subject: Re: [PATCHSET v5 sched_ext/for-7.3] sched_ext: Capability-based CPU delegation for sub-schedulers In-Reply-To: References: <20260709225041.1695495-1-tj@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Hello, Andrea. On Tue, Jul 14, 2026 at 09:10:13AM +0200, Andrea Righi wrote: > I went through the series and tested the resulting kernel under virtme-ng. I > couldn't trigger any crashes, lockups, or warnings, and I don't see any issues > that should block applying this. > > As I mentioned, one possible follow-up optimization would be to introduce a > "scx_has_sub_scheds" static key, indicating whether any sub-scheduler is > attached. This could preserve the current fast paths for the common case of a > single root-only scheduler, avoiding the small potential overhead of > sub-scheduler-specific hierarchy walks and capability checks. And it could also > enable additional optimizations in the future. Yeah, gating the sub-sched-only paths behind a static key while no sub-scheduler is attached is on the todo list. Will follow up with incremental patches. > For the series: > > Reviewed-by: Andrea Righi Thanks a lot for the review and testing. -- tejun