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 X-Spam-Level: X-Spam-Status: No, score=-3.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_NEOMUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D6AA6C282C0 for ; Fri, 25 Jan 2019 23:44:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A5D83218D0 for ; Fri, 25 Jan 2019 23:44:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="olBz/Sc+" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728657AbfAYXoI (ORCPT ); Fri, 25 Jan 2019 18:44:08 -0500 Received: from mail-pf1-f194.google.com ([209.85.210.194]:41608 "EHLO mail-pf1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726218AbfAYXoI (ORCPT ); Fri, 25 Jan 2019 18:44:08 -0500 Received: by mail-pf1-f194.google.com with SMTP id b7so5433003pfi.8 for ; Fri, 25 Jan 2019 15:44:07 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=Y2ashjkyhVK0FhA6aTbWjkzY9tEXbAaGGCL2aX2DVYY=; b=olBz/Sc+9EJl15rCf15m+wfeb/B9p/LENGp93VM4NsyGYOnqP9Mmc9lzKOTYhgEL2P 46mf8g3SsX64sVDQhDhhtebh+okVKbMwX9gpig2WMoNgIwx4Cy+/TNgvvxcP8f01GVEk 3Og7JYKoD3H3vdyLN1N+LBkF9fZf0SIlkR8nFiQP1jitOaDKjkMVDHtL/K7QnABPLxVP YhuPpaPlFNBjE2RnRUMHVy0lmE/nwC7A6ED2scH3sBhACy8DMDMupBjl5RgAaojC+azV /tUPc6B27wicLzMYyrZIG8qIvxIHMKqczt7Et2GeMxbI73xgQs3zvv+pU/y+PGavlURu Xqvw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=Y2ashjkyhVK0FhA6aTbWjkzY9tEXbAaGGCL2aX2DVYY=; b=Gga93gYczhvHflKdRWnuIAvMiDY0jV6Lcse26hCfigePNIjck/Bx6tYjbu4+33opNh Wm2fDPlh1n4/oTWJbTcwQRiit4Z2Sy3cnUUHLPr13k3RSe/aVtawAX60S1uKyv/OA2BZ T0cR5YjuRLXfUgcLjQOwVqPTpPDYYTjX2SnfufHMRKolB7Xg3XP+1NUZ5OOVZILoNBhh F63PoS69Nrc3p65qPYOjKjYwQnAubH3g5ldzejsg3A2ayOuns5Cnl24EZR1qgWwV0z1x fBl0IWGNKHbO2QaX++qNR/1a+sNBzMOsLt7FzosqFAC5pTkL7NRnFmR/fYgfMSR7Zt8y GcrQ== X-Gm-Message-State: AJcUukcaJt5yls59VQZcCMusFDZKQBZAcFvmU9XFlLeYLruWW5tssSIz uJQIJRZBJYFtVEN7Fi4IHrI= X-Google-Smtp-Source: ALg8bN7gntD0ANiURRpRGz8eFQSB6nG/fT8HvoCiwwQwj7TgoeUPrUqJ0kIJ3K4vH8D4rN77OvuQiA== X-Received: by 2002:a62:68c5:: with SMTP id d188mr13354551pfc.194.1548459847034; Fri, 25 Jan 2019 15:44:07 -0800 (PST) Received: from ast-mbp.dhcp.thefacebook.com ([2620:10d:c090:200::7:19a8]) by smtp.gmail.com with ESMTPSA id m65sm62602609pfg.180.2019.01.25.15.44.05 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 25 Jan 2019 15:44:06 -0800 (PST) Date: Fri, 25 Jan 2019 15:44:05 -0800 From: Alexei Starovoitov To: "Paul E. McKenney" Cc: Jann Horn , Peter Zijlstra , Alexei Starovoitov , "David S. Miller" , Daniel Borkmann , jakub.kicinski@netronome.com, Network Development , kernel-team@fb.com, Ingo Molnar , Will Deacon Subject: Re: [PATCH v4 bpf-next 1/9] bpf: introduce bpf_spin_lock Message-ID: <20190125234403.iisj5woztm4afwgh@ast-mbp.dhcp.thefacebook.com> References: <20190124041403.2100609-2-ast@kernel.org> <20190124180109.GA27771@hirez.programming.kicks-ass.net> <20190124185652.GB17767@hirez.programming.kicks-ass.net> <20190124234232.GY4240@linux.ibm.com> <20190125000515.jizijxz4n735gclx@ast-mbp.dhcp.thefacebook.com> <20190125012224.GZ4240@linux.ibm.com> <20190125041152.GA4240@linux.ibm.com> <20190125225112.GF4240@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190125225112.GF4240@linux.ibm.com> User-Agent: NeoMutt/20180223 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Fri, Jan 25, 2019 at 02:51:12PM -0800, Paul E. McKenney wrote: > > > > > > So no more than (say) 100 milliseconds? > > > > Depends on RLIMIT_MEMLOCK and on how hard userspace is trying to make > > things slow, I guess - if userspace manages to create a hashtable, > > with a few dozen megabytes in size, with worst-case assignment of > > elements to buckets (everything in a single bucket), every lookup call > > on that bucket becomes a linked list traversal through a list that > > must be stored in main memory because it's too big for the CPU caches. > > I don't know into how much time that translates. > > So perhaps you have a candidate BPF program for the RCU CPU stall warning > challenge, then. ;-) I'd like to see one that can defeat jhash + random seed.