From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (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 22693471D06; Fri, 28 Aug 2026 14:45:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787928316; cv=none; b=Op6sVEdLBa8AAJSwcEj9CUf4Vy6J5vA5FBOVE30w9wOv6ukDx1Jjp21HH2iKlNVwxeXjxEwfNY+PHW2rN0VH83xQgu8ZI2UBk0BwDn2qykd6HIRx9IvjsfKsARIedqIjFpzKR5xFaBc/ylX5VzUhV+RQPUPAxNjdsUaqGwW7jWQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787928316; c=relaxed/simple; bh=soZ9PL61goEMOkaDJT6p0gnMZMgrTdoK6hpq+e4lLlU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=BlpK1GmrSkD4zqZRGZknmuJ+xXVFA12bSuJOOAlqNfHBisbWVBWNDat+iMEh589UI+GDWBkZ1xwmVJArpFcYblIpzOILM7KK2oP5z4plYXe+MydLSlhjrmz/tr6I+gJvvWkhMWsz8Jrnq0BNwbfY9jlrdrNmZlCHd+3+i1HMkkM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=pass smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=Au9yP3eB; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=pass 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="Au9yP3eB" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; 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=2svEyFOZsFh7Z9gUJnKXJmkUHjn+t2fc++fT9yfnVTw=; b=Au9yP3eB6i4vjvt53lDNHwLHlH 7GVgsID/l2OoVPVxPQoAzsrTgC8xDr62Gl7PzX36y4pzO91NYooNY0VRMTX25aDzYsXrWhSrKBfD3 eEknGtS+cIS2Jfadq9c5/IK4QycHdXAqPY9FFegcrduJNbHVrhcWLe8n2+/j92MRChzgCnB+QWMLc kS9VFW/sxoqKApZL2rhQ7eCkQjZcGfK+3oIXe6z752aOnqF9Fxgl/p5zCePvciTBNIXYBjU26qejO l16qPsRAMGjpvTTFFhkVoUX+1zgiHnca29azGuoTY/oUB/KYztdt9eCJlLUFx8X7gHVqh1JO7kz5T BFCChTlw==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.99.1 #2 (Red Hat Linux)) id 1wzxpF-0000000EqNL-1I6b; Fri, 28 Aug 2026 14:45:01 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id C4B2930116A; Fri, 28 Aug 2026 16:45:00 +0200 (CEST) Date: Fri, 28 Aug 2026 16:45:00 +0200 From: Peter Zijlstra To: Steven Rostedt Cc: David Stevens , Catalin Marinas , Will Deacon , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H . Peter Anvin" , Andrew Morton , Dave Chinner , Qi Zheng , Roman Gushchin , Muchun Song , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Ben Segall , Mel Gorman , Valentin Schneider , K Prateek Nayak , Uladzislau Rezki , David Hildenbrand , Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kees Cook , Sebastian Andrzej Siewior , Clark Williams , suleiman@google.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-rt-devel@lists.linux.dev, jstultz@google.com Subject: Re: [RFC 00/10] Reclaimable kernel stacks Message-ID: <20260828144500.GW776954@noisy.programming.kicks-ass.net> References: <20260827232948.2520558-1-stevensd@google.com> <20260828124758.GP687043@noisy.programming.kicks-ass.net> <20260828103328.633bbfbc@gandalf.local.home> <20260828143540.GV776954@noisy.programming.kicks-ass.net> Precedence: bulk X-Mailing-List: linux-rt-devel@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260828143540.GV776954@noisy.programming.kicks-ass.net> On Fri, Aug 28, 2026 at 04:35:40PM +0200, Peter Zijlstra wrote: > On Fri, Aug 28, 2026 at 10:33:28AM -0400, Steven Rostedt wrote: > > On Fri, 28 Aug 2026 14:47:58 +0200 > > Peter Zijlstra wrote: > > > > > > On Android, system processes typically have 2000-3000 threads. App > > > > processes add 1000s more threads on top of this. > > > > > > WTF ?!? Why does that all spawn *that* many threads? Perhaps work on > > > reducing that some? > > > > I guess you never ran Java ;-) > > Of course not; why would you want to do something that silly ;-) I realized I actually have a Java thing, the kids have Minecraft, so I booted that up and I found all of 108 threads. Which is still kinda insane, but nowhere near the 1000s per app as claimed. Reducing the thread count from O(1e3) to O(1e2) would win far more memory than any thread stack shenanigans would.