From owner-freebsd-virtualization@freebsd.org Fri Mar 3 15:40:55 2017 Return-Path: Delivered-To: freebsd-virtualization@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 2C51BCF6118 for ; Fri, 3 Mar 2017 15:40:55 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org (kenobi.freebsd.org [IPv6:2001:1900:2254:206a::16:76]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 137571FCC for ; Fri, 3 Mar 2017 15:40:55 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from bugs.freebsd.org ([127.0.1.118]) by kenobi.freebsd.org (8.15.2/8.15.2) with ESMTP id v23Fesxe095959 for ; Fri, 3 Mar 2017 15:40:54 GMT (envelope-from bugzilla-noreply@freebsd.org) From: bugzilla-noreply@freebsd.org To: freebsd-virtualization@FreeBSD.org Subject: [Bug 216759] [kern] Memory speed with small blocks (1K) up to 35 times slower than host system (under QEMU emulation, but not only) Date: Fri, 03 Mar 2017 15:40:55 +0000 X-Bugzilla-Reason: AssignedTo X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: Base System X-Bugzilla-Component: kern X-Bugzilla-Version: 11.0-RELEASE X-Bugzilla-Keywords: X-Bugzilla-Severity: Affects Many People X-Bugzilla-Who: bob.cauthen@gmail.com X-Bugzilla-Status: New X-Bugzilla-Resolution: X-Bugzilla-Priority: --- X-Bugzilla-Assigned-To: freebsd-virtualization@FreeBSD.org X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: https://bugs.freebsd.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-BeenThere: freebsd-virtualization@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: "Discussion of various virtualization techniques FreeBSD supports." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 03 Mar 2017 15:40:55 -0000 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D216759 --- Comment #13 from bob.cauthen@gmail.com --- As an interested party to this bug I have to raise an issue with this poten= tial workaround. First though... thanks everybody who discovered and tested this... BUT According to timecounters(4): kern.timecounter.tc.X.quality is an integral value, defining the quali= ty of this time counter compared to others. A negative value means this time counter is broken and should not be used. Andrew's test output showed this line: Timecounter "TSC-low" frequency 1700064513 Hz quality -100 If the workaround forces the use of TSC-low, and it's kern.timecounter.tc.X.quality is negative, are we not advocating a workarou= nd with a broken timecounter as measured by the OS? If the answer is yes (to my rhetorical question) possible follow-up questio= ns might then be: - Should we trust the negative "quality" measurement? (if not, maybe it's easier to mod the timecounter measurement code??) - Has anyone done any longer term testing with the TSC-low timer in this configuration to see if using that time counter effects anything else in a running system? Sorry to be the opposing voice here (especially because this bug affects me too). --=20 You are receiving this mail because: You are the assignee for the bug.=