From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=5.0 tests=DKIM_INVALID,DKIM_SIGNED, MAILING_LIST_MULTI,RCVD_IN_DNSWL_NONE autolearn=ham autolearn_force=no version=3.4.4 Received: (qmail 727 invoked from network); 5 Feb 2021 05:18:38 -0000 Received: from minnie.tuhs.org (45.79.103.53) by inbox.vuxu.org with ESMTPUTF8; 5 Feb 2021 05:18:38 -0000 Received: by minnie.tuhs.org (Postfix, from userid 112) id 0DAFF9C7B6; Fri, 5 Feb 2021 15:18:35 +1000 (AEST) Received: from minnie.tuhs.org (localhost [127.0.0.1]) by minnie.tuhs.org (Postfix) with ESMTP id A17229BA40; Fri, 5 Feb 2021 15:18:03 +1000 (AEST) Authentication-Results: minnie.tuhs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=iitbombay-org.20150623.gappssmtp.com header.i=@iitbombay-org.20150623.gappssmtp.com header.b="Tv1atAg5"; dkim-atps=neutral Received: by minnie.tuhs.org (Postfix, from userid 112) id 676DD9BA40; Fri, 5 Feb 2021 15:17:59 +1000 (AEST) Received: from mail-oi1-f173.google.com (mail-oi1-f173.google.com [209.85.167.173]) by minnie.tuhs.org (Postfix) with ESMTPS id 278469BA3F for ; Fri, 5 Feb 2021 15:17:58 +1000 (AEST) Received: by mail-oi1-f173.google.com with SMTP id w124so6309202oia.6 for ; Thu, 04 Feb 2021 21:17:58 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=iitbombay-org.20150623.gappssmtp.com; s=20150623; h=content-transfer-encoding:from:mime-version:subject:date:message-id :references:cc:in-reply-to:to; bh=O7b9z+Lv9vu9csvu98E1DJ8UBrUnR6i8GpvrTi7RLAg=; b=Tv1atAg5/YcXW3A7n18cUIVPr/9G0R3+t9UouMt/CODHUyqj4d+HyHdfJBseSjGDkm mPnRiw2iDnSQc9dn4i8VkgzSSpxv7Kejt30C66xW0OiUg6kGfwKLYkQDldlja5hjzyac cnRMXxUJ7ao2RX9obrFPN3qzKqiqDoRRGi+8GBLKz4t5kaEChwV7ZMkrP6+jtNBsvpJD jLEvvCe3ppvBKstM2ykyENTpp5r+NRtJpAxxySu1GMK/4FywFDcdqNgP55h9ta4YCs5I EkiomWv/6yBGOjRK8Ve1Pt9WLGFh45vlI7b5cY6NjQJxeGjRtLGR8QL8aVE+Qpo9QGhU 83Jw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:content-transfer-encoding:from:mime-version :subject:date:message-id:references:cc:in-reply-to:to; bh=O7b9z+Lv9vu9csvu98E1DJ8UBrUnR6i8GpvrTi7RLAg=; b=TkTLlPiXvSERCFeIm35gCbteQShAplgNXIMHzXyW9GTraPpVilefdQfieqUWol5qJL zBARH3DWi18C2jhyYvMRzkw1tkSE9GC3IMgD4V/b9tQSTv/PPjyyGiOrhtkYu7pE7+nP R5tGS5WpyhA3EFvnY9ZLbOUqUfpY+7iEa+OBafXkYuAU5vlAo3lbdXfOVLu8WEl9LVoc 1OFEcNRtwrcLFZkmCuRcCVNkpPXeN8aevL+dfITzm/FqcrjdmG9tCJi8fJIMTPmLhTtU YdOTBDRf/DDubiOtc633yJCoHjaCMotsPDUkz1r8MRKMMRNiBQoMhsrDcNoFUKnTOohV WA2A== X-Gm-Message-State: AOAM533ZIhcy5GwP6KWJjUjIZhppzviuObO0VoPUpS8f74Ji+1ccxYJ+ 2X85QY2wKEyohEHBf4EY5guXIQ== X-Google-Smtp-Source: ABdhPJyk0d2IySUtF3peMMmw2hKIZVdjFS3WgbF7mlRqBuzlOpd58J+uZ2C2fUsS5UZXMZnLTwvqFA== X-Received: by 2002:aca:b1c1:: with SMTP id a184mr2007787oif.117.1612502277136; Thu, 04 Feb 2021 21:17:57 -0800 (PST) Received: from [192.168.1.110] (172-125-77-130.lightspeed.sntcca.sbcglobal.net. [172.125.77.130]) by smtp.gmail.com with ESMTPSA id o14sm1630763oof.38.2021.02.04.21.17.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 04 Feb 2021 21:17:55 -0800 (PST) Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable From: Bakul Shah Mime-Version: 1.0 (1.0) Date: Thu, 4 Feb 2021 21:17:54 -0800 Message-Id: <26D923CF-5319-4207-BA28-6EFA0E3BB1F8@iitbombay.org> References: <20210205003315.GK13701@mcvoy.com> In-Reply-To: <20210205003315.GK13701@mcvoy.com> To: Larry McVoy X-Mailer: iPad Mail (18D52) Subject: Re: [TUHS] FreeBSD behind the times? (was: Favorite unix design principles?) X-BeenThere: tuhs@minnie.tuhs.org X-Mailman-Version: 2.1.26 Precedence: list List-Id: The Unix Heritage Society mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: TUHS main list Errors-To: tuhs-bounces@minnie.tuhs.org Sender: "TUHS" On Feb 4, 2021, at 4:33 PM, Larry McVoy wrote: >=20 > Ignoring the page cache and make their own cache has big problems. > You can mmap() ZFS files and doing so means that when a page is referenced= > it is copied from the ZFS cache to the page cache. That creates a > coherency problem, I can write via the mapping and I can write via > write(2) and now you have two copies of the data that don't match, > that's pretty much OS no-no #1. Write(2)ing to a mapped page sounds pretty dodgy. Likely to get you in trouble in any case. Similarly read(2)ing. And you can keep track of mapped pages and read/write from them if necessary even if you have a separate cache for any compressed pages. I haven=E2=80=99t read zfs code but this doesn=E2=80=99t seem like a tricky problem.=