From owner-freebsd-hackers@freebsd.org Wed Sep 13 17:24:28 2017 Return-Path: Delivered-To: freebsd-hackers@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 2525AE06D72 for ; Wed, 13 Sep 2017 17:24:28 +0000 (UTC) (envelope-from wlosh@bsdimp.com) Received: from mailman.ysv.freebsd.org (mailman.ysv.freebsd.org [IPv6:2001:1900:2254:206a::50:5]) by mx1.freebsd.org (Postfix) with ESMTP id F27476F435 for ; Wed, 13 Sep 2017 17:24:27 +0000 (UTC) (envelope-from wlosh@bsdimp.com) Received: by mailman.ysv.freebsd.org (Postfix) id F1B61E06D6F; Wed, 13 Sep 2017 17:24:27 +0000 (UTC) Delivered-To: hackers@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id F1484E06D6D for ; Wed, 13 Sep 2017 17:24:27 +0000 (UTC) (envelope-from wlosh@bsdimp.com) Received: from mail-io0-x229.google.com (mail-io0-x229.google.com [IPv6:2607:f8b0:4001:c06::229]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id B9B636F434 for ; Wed, 13 Sep 2017 17:24:27 +0000 (UTC) (envelope-from wlosh@bsdimp.com) Received: by mail-io0-x229.google.com with SMTP id n69so4899768ioi.5 for ; Wed, 13 Sep 2017 10:24:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bsdimp-com.20150623.gappssmtp.com; s=20150623; h=mime-version:sender:in-reply-to:references:from:date:message-id :subject:to:cc; bh=619AVfm25gEAAsH7nF28tSbhzeJN7xLy5R1xdEFGkwU=; b=ZSbLndx/SJGlOmjj21RDcreY10UfDPYC4n1UzCrkukSYLXNRT071LTNzh9nB7G4s2F I1WnsEUil3znmxPLHMFlZNiM0KAPFL37/ELXmWwiYjpiE6Ba89ztKBdQKOr/RN6nYc7j tuOSI8WycoLvZ37QPnliOyG+wGIeRawzrB+zlFrirPmjfgA+7s5cnXQl4+ryvfRvepJZ I+y9+IgjoBOi2sfSEhYcjo5etOU83yzMpn9T/bdBjEBEdZxc2vWj2LBj10nzXrVUhZ/X WCBaixgj7CjnT4Vn9Nrlvg5v/s1UGD+jpqDxO4YOruKAYoxt6h0ebff8VUmm6dYP33AC OItQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:sender:in-reply-to:references:from :date:message-id:subject:to:cc; bh=619AVfm25gEAAsH7nF28tSbhzeJN7xLy5R1xdEFGkwU=; b=FRKCwbLfq8K9XWZYqGrIGvoncW4Optt0CKPW1yJJYadtz8uckmeLgvguGHgy2zrQrn 9yKG/xMC2UnqZL25nryoCc54ijdAy19b1FyX7waP8zEK6WEDDb2yZS/esYYcdI48UMg8 L6BMlxTSyz2c8to8qB7XLGxxlJsvb8jkokCRlVB1C26PQ/THLp0dyd2TKPijXwExDFkm QnlEjz5LtvtwNT4d9esTL+Pf6LFB9HmQ9amiZ3bMfaz7vdIorDdjtpthEqpF+k133SCJ /9sZujg//bmrlTiTkc4nAI/AjhKV0Z0YFQNl8Knyj7h5LJ1Z3ypMedjHg2ljFUbD3i+X FiTQ== X-Gm-Message-State: AHPjjUheGdL50AVrDtJtTHDB3TXkRJGrDJeongmBoGqdhC4fpGaRFwzb EPN7RdLUV+t1d+I91UjPuc1xqm20w6iL5cfs9BsFQQ== X-Google-Smtp-Source: AOwi7QCgpbUrZPlgWqFT7C5MNDFkwl5LErY6NHP/ro1U0CfW5HVsC9a5ntgFBeQmVAdQWjY7mMCjaw9XhqIkWfkxIx4= X-Received: by 10.107.135.147 with SMTP id r19mr25478480ioi.26.1505323467166; Wed, 13 Sep 2017 10:24:27 -0700 (PDT) MIME-Version: 1.0 Sender: wlosh@bsdimp.com Received: by 10.79.10.71 with HTTP; Wed, 13 Sep 2017 10:24:26 -0700 (PDT) X-Originating-IP: [2603:300b:6:5100:60a7:d7e6:aef8:c203] In-Reply-To: References: <20170913155542.GA25871@mail.michaelwlucas.com> From: Warner Losh Date: Wed, 13 Sep 2017 11:24:26 -0600 X-Google-Sender-Auth: S9TsR6D1tkhA-hEJBv-X5bVNcMI Message-ID: Subject: Re: required kernel rebuilds To: Alan Somers Cc: "Michael W. Lucas" , "freebsd-hackers@freebsd.org" Content-Type: text/plain; charset="UTF-8" X-Content-Filtered-By: Mailman/MimeDel 2.1.23 X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 13 Sep 2017 17:24:28 -0000 On Wed, Sep 13, 2017 at 10:07 AM, Alan Somers wrote: > On Wed, Sep 13, 2017 at 9:55 AM, Michael W. Lucas > wrote: > > Hi, > > > > Book research question. > > > > Way back in the Dark Ages of the 1990s, it wasn't uncommon to rebuild > > a kernel to fix a recurring panic. You'd have to tune MAXUSERS, or > > PMAP_SHPGPERPROC. > > > > AFAIK, dang near everything is tunable in either loader.conf or > > sysctl.conf. I really want to say that kernel rebuilds for these kinds > > of limits aren't needed any more. > > > > Does anyone have a counter-example, though? Is anything possibly > > crash-inducing non-tunable without a kernel rebuild? > > > > Thanks, > > ==ml > > Enabling VIMAGE still requires a kernel rebuild, because of the > possibility of crashes. I've seen such crashes on 10.2 or 10.3. I > don't know if they're fixed in 11.1, but I haven't seen any yet. > Changing MAXPHYS also requires a kernel rebuild. AFAIK MAXPHYS isn't > related to any kernel crashes, but it does have performance > implications. > MAXPHYS isn't currently dynamic. We have to set it at Netflix because we want to do super large I/Os. We'd just bump it in base, but it requires extra memory for every single I/O (since there's arrays in struct buf / bio based on this size for pages related to the I/O). I've had one kernel panic that was fixed by changing MAXPHYS, but that was due to a stupid driver bug... Warner