Return-Path: <awaresystems.be+caf_=filtered=awaresystems.be@gmail.com>
Delivered-To: filtered@awaresystems.be
Received: from mx2.pub.mailpod2-cph3.one.com ([10.27.25.12])
	by mailstorage18.cst.mailpod2-cph3.one.com (Dovecot) with LMTP id DKMKM1VGXVoD/gAAQS8vrQ
	for <filtered@awaresystems.be>; Tue, 16 Jan 2018 00:30:35 +0000
X-HalOne-ID: 7768c6dd-fa54-11e7-b104-ec0d9a6ed9fe
Received: from mail-oi0-f43.google.com (unknown [209.85.218.43])
	by mx2.pub.mailpod2-cph3.one.com (Halon) with ESMTPS
	id 7768c6dd-fa54-11e7-b104-ec0d9a6ed9fe;
	Tue, 16 Jan 2018 00:30:35 +0000 (UTC)
Received: by mail-oi0-f43.google.com with SMTP id t16so9451949oif.10
        for <filtered@awaresystems.be>; Mon, 15 Jan 2018 16:30:35 -0800 (PST)
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
        d=1e100.net; s=20161025;
        h=x-original-authentication-results:x-gm-message-state:delivered-to
         :date:from:to:in-reply-to:message-id:references:user-agent
         :mime-version:cc:subject:precedence:list-id:list-unsubscribe
         :list-archive:list-post:list-help:list-subscribe
         :content-transfer-encoding:sender:errors-to;
        bh=YRFo3qxfhMB81QGim7B9xopfoTrTV8lA5KaYyCZGPGU=;
        b=Gs3eroe7tBUa4W7Q3naHtYWipOBSc0FXn+SjvMmzMyyeBwOmMm0V48P0Ci+ppm6s+a
         d5JpzaAp+mrIEz9zMr02eJlaC4P5fcsYvVzqN2/W0cA4/oQBB0cxcNhSDnQs9M/OzxO6
         kSxJbw2UszIPRWkMikokubc8kQP9bUWgzj3nbqjSxg+2R3XdgvgW9Ab8G/pDjqjb5AK8
         rsJpbIBRT2zsxyD9m1qAXCsnMd9eccf//Nipps6mzGUwJGfyXSoqt3eMQMQgQn3treXC
         hu8G80MWZdZ+CmeRZsZKfIAoONA1GV48HUTB5Q7y5vIATL2JEH4t85C3I/eQFJdwbRGC
         Q0uA==
X-Original-Authentication-Results: mx.google.com;       spf=neutral (google.com: 94.23.4.142 is neither permitted nor denied by best guess record for domain of tiff-bounces@lists.maptools.org) smtp.mailfrom=tiff-bounces@lists.maptools.org
X-Gm-Message-State: AKwxytcoHzkZkylj686P2Lrg3tbU9gBYJbMNLlYpsFuLLzJVSHdZ3yGn
	KmO90WhkupRwn7gaSZ3o/2mrXabcGk68bUK4opKnawBNl770jsk=
X-Received: by 10.202.195.67 with SMTP id t64mr2612182oif.29.1516062634105;
        Mon, 15 Jan 2018 16:30:34 -0800 (PST)
X-Forwarded-To: filtered@awaresystems.be
X-Forwarded-For: awaresystems.be@gmail.com filtered@awaresystems.be
Delivered-To: awaresystems.be@gmail.com
Received: by 10.202.235.11 with SMTP id j11csp3505047oih;
        Mon, 15 Jan 2018 16:30:32 -0800 (PST)
X-Google-Smtp-Source: ACJfBoumFti1BKo2EMoNmrVvEdNipr/p9sjrHNVQzSP61bHXMnJAN0O77A7mEiGf9nmXucDddgtw
X-Received: by 10.223.131.166 with SMTP id 35mr6270377wre.221.1516062632915;
        Mon, 15 Jan 2018 16:30:32 -0800 (PST)
ARC-Seal: i=1; a=rsa-sha256; t=1516062632; cv=none;
        d=google.com; s=arc-20160816;
        b=Bb6ryMEiEYxvyFLxoAKOa6KCp557NDkG4Yw7+QW2l6gniPvEtPKaaFFnIIf1dqxJUN
         dJ0i/IOf2yN5qpmbjc9yTnzCWg9QmO4/a9ky5z1vN/mrCR1Wn6SaMNNwZ4SLRngK1n9m
         fZTXQmSkeIMi1r3Ovil1SgcShrueT1nsiTxuTfragTd5yBqbYKKOgi0FCegsnw7Mx+8U
         es+WqnEXoX0U1ullWX3XQbJYyzgh5IWnzYYEfoEwOtPtJFmHHBj7Ki6UDc/75LFm/QJa
         T1XxpSjMwZcMXR+hrIi9cHDe5DZtz7cqz0nMJ3I0iWxcGw8FuT++fFQAAyZ2SOmPyhaM
         IOAQ==
ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816;
        h=errors-to:sender:content-transfer-encoding:list-subscribe:list-help
         :list-post:list-archive:list-unsubscribe:list-id:precedence:subject
         :cc:mime-version:user-agent:references:message-id:in-reply-to:to
         :from:date:arc-authentication-results;
        bh=YRFo3qxfhMB81QGim7B9xopfoTrTV8lA5KaYyCZGPGU=;
        b=nSubYT96QowcMmW91hFshv1wFLXyUF1exRVUXSTykc5jbLe3vI9Om/CODLTFClQ/VV
         kgRloU4CajqrmK2idwNwAk7d4+guG8ONvo/WIP2uxnYyccDEiVik7FvNoO/8HZFTcvcQ
         vXmDL29c1SOt8PhaJ42GbYxcPyeV3/SbH3Q8dlNqJAG+c2la621aSFQ6qzJB8Cs1qkc4
         B+JbT3Q+EuG20XG03fmvgmJeCUU+KbA7FUUeOcL3oTKY8XCCQwHAoafWVS09IWPbcNl7
         wiRHSd6DbI3/Hxnfbr9DA5/FeDycyFKqk76MN6TdJbQ8Yq/eFhwGSEmKhGIEtQ/OShit
         b4ww==
ARC-Authentication-Results: i=1; mx.google.com;
       spf=neutral (google.com: 94.23.4.142 is neither permitted nor denied by best guess record for domain of tiff-bounces@lists.maptools.org) smtp.mailfrom=tiff-bounces@lists.maptools.org
Return-Path: <tiff-bounces@lists.maptools.org>
Received: from lists.maptools.org (ks365428.kimsufi.com. [94.23.4.142])
        by mx.google.com with ESMTP id 62si774113wrm.70.2018.01.15.16.30.32;
        Mon, 15 Jan 2018 16:30:32 -0800 (PST)
Received-SPF: neutral (google.com: 94.23.4.142 is neither permitted nor denied by best guess record for domain of tiff-bounces@lists.maptools.org) client-ip=94.23.4.142;
Authentication-Results: mx.google.com;
       spf=neutral (google.com: 94.23.4.142 is neither permitted nor denied by best guess record for domain of tiff-bounces@lists.maptools.org) smtp.mailfrom=tiff-bounces@lists.maptools.org
Received: from [10.1.0.241] (localhost.localdomain [127.0.0.1])
	by lists.maptools.org (Postfix) with ESMTP id 2FE7735C07F;
	Mon, 15 Jan 2018 19:29:39 -0500 (EST)
Received: from smtp.simplesystems.org (smtp.simplesystems.org [65.66.246.90])
	by lists.maptools.org (Postfix) with ESMTPS id AC82635C07E
	for <tiff@lists.maptools.org>; Mon, 15 Jan 2018 19:24:05 -0500 (EST)
Received: from scrappy.simplesystems.org (scrappy.simplesystems.org
	[65.66.246.73])
	by smtp.simplesystems.org (8.14.4+Sun/8.14.4) with ESMTP id
	w0G0O0hQ004555; Mon, 15 Jan 2018 18:24:00 -0600 (CST)
Date: Mon, 15 Jan 2018 18:24:00 -0600 (CST)
From: Bob Friesenhahn <bfriesen@simple.dallas.tx.us>
X-X-Sender: bfriesen@scrappy.simplesystems.org
To: Larry Gritz <lg@larrygritz.com>
In-Reply-To: <D4C4B1FE-4C28-4E7C-964F-750BBCF87DAC@larrygritz.com>
Message-ID: <alpine.GSO.2.20.1801151816490.18206@scrappy.simplesystems.org>
References: <39EE49FE-23A5-43DE-8998-51526287D182@larrygritz.com>
	<alpine.GSO.2.20.1801151400550.18206@scrappy.simplesystems.org>
	<4252FC16-C07D-4FA1-8B7B-25D626633236@larrygritz.com>
	<F78FB533EE93A044B560CD25E17A4DAF18388904@mbx031-e1-va-4.exch031.domain.local>
	<D4C4B1FE-4C28-4E7C-964F-750BBCF87DAC@larrygritz.com>
User-Agent: Alpine 2.20 (GSO 67 2015-01-07)
MIME-Version: 1.0
X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16
	(smtp.simplesystems.org [65.66.246.90]);
	Mon, 15 Jan 2018 18:24:00 -0600 (CST)
Cc: "tiff@lists.maptools.org" <tiff@lists.maptools.org>
Subject: Re: [Tiff] Strategies for multi-core speedups
X-BeenThere: tiff@lists.maptools.org
X-Mailman-Version: 2.1.9
Precedence: list
List-Id: TIFF and libtiff discussion <tiff.lists.maptools.org>
List-Unsubscribe: <http://lists.maptools.org/mailman/listinfo/tiff>,
	<mailto:tiff-request@lists.maptools.org?subject=unsubscribe>
List-Archive: <http://lists.maptools.org/mailman/private/tiff>
List-Post: <mailto:tiff@lists.maptools.org>
List-Help: <mailto:tiff-request@lists.maptools.org?subject=help>
List-Subscribe: <http://lists.maptools.org/mailman/listinfo/tiff>,
	<mailto:tiff-request@lists.maptools.org?subject=subscribe>
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Sender: tiff-bounces@lists.maptools.org
Errors-To: tiff-bounces@lists.maptools.org

On Mon, 15 Jan 2018, Larry Gritz wrote:

> There is no mystery here -- the I/O itself is still serialized, so 
> if it's only 10% of the total runtime, say, even perfectly linear 
> thread scaling and an unlimited number of cores without any lock 
> contention will experience a maximum of 10x improvement. Amdahl's 
> Law and all that. That effect alone adequately explains my lack of 
> thread scalability beyond 8 or so cores, for this application.

The I/O is not necessarily serialized.  When using mmap, pread/pwrite, 
or asynchronous I/O, the I/O can also benefit from multi-threading 
given that the underlying storage is a multi-disk array or SSDs using 
PCIe NVMe (capable of up to 1024 simultaneous I/Os).

Amdahl's Law still applies. :-)

Bob
-- 
Bob Friesenhahn
bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/
_______________________________________________
Tiff mailing list: Tiff@lists.maptools.org
http://lists.maptools.org/mailman/listinfo/tiff
http://www.remotesensing.org/libtiff/
