From owner-freebsd-hackers@freebsd.org Mon Jul 4 23:45:54 2016 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 8C369B9135A for ; Mon, 4 Jul 2016 23:45:54 +0000 (UTC) (envelope-from mmacy@nextbsd.org) Received: from sender163-mail.zoho.com (sender163-mail.zoho.com [74.201.84.163]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 7DFF72E23 for ; Mon, 4 Jul 2016 23:45:54 +0000 (UTC) (envelope-from mmacy@nextbsd.org) Received: from mail.zoho.com by mx.zohomail.com with SMTP id 1467675943133327.7328959933959; Mon, 4 Jul 2016 16:45:43 -0700 (PDT) Date: Mon, 04 Jul 2016 16:45:43 -0700 From: Matthew Macy To: "Karl Denninger" Cc: "" Message-ID: <155b84da0aa.ad3af0e6139335.8627172617037605875@nextbsd.org> In-Reply-To: <45865ae6-18c9-ce9a-4a1e-6b2a8e44a8b2@denninger.net> References: <20160630140625.3b4aece3@splash.akips.com> <20160703123004.74a7385a@splash.akips.com> <155afb8148f.c6f5294d33485.2952538647262141073@nextbsd.org> <45865ae6-18c9-ce9a-4a1e-6b2a8e44a8b2@denninger.net> Subject: Re: ZFS ARC and mmap/page cache coherency question MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Priority: Medium User-Agent: Zoho Mail X-Mailer: Zoho Mail X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.22 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 04 Jul 2016 23:45:54 -0000 ---- On Sun, 03 Jul 2016 08:43:19 -0700 Karl Denninger wrote ---- > > On 7/3/2016 02:45, Matthew Macy wrote: > > > > Cedric greatly overstates the intractability of resolving it. Nonetheless, since the initial import very little has been done to improve integration, and I don't know of anyone who is up to the task taking an interest in it. Consequently, mmap() performance is likely "doomed" for the foreseeable future.-M---- > > Wellllll.... > > I've done a fair bit of work here (see > https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=187594) and the > political issues are at least as bad as the coding ones. > Strictly speaking, the root of the problem is the ARC. Not ZFS per se. Have you ever tried disabling MFU caching to see how much worse LRU only is? I'm not really convinced the ARC's benefits justify its cost. -M