From owner-freebsd-arch@FreeBSD.ORG Wed Feb 25 07:55:21 2015 Return-Path: Delivered-To: freebsd-arch@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 8CA71285; Wed, 25 Feb 2015 07:55:21 +0000 (UTC) Received: from elvis.mu.org (elvis.mu.org [192.203.228.196]) by mx1.freebsd.org (Postfix) with ESMTP id 73519B4F; Wed, 25 Feb 2015 07:55:20 +0000 (UTC) Received: from AlfredMacbookAir.local (unknown [12.133.26.10]) by elvis.mu.org (Postfix) with ESMTPSA id ABC57341F8B1; Tue, 24 Feb 2015 23:55:19 -0800 (PST) Message-ID: <54ED80BD.1080603@freebsd.org> Date: Wed, 25 Feb 2015 02:58:53 -0500 From: Alfred Perlstein Organization: FreeBSD User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:31.0) Gecko/20100101 Thunderbird/31.4.0 MIME-Version: 1.0 To: John-Mark Gurney , "K. Macy" Subject: Re: locks and kernel randomness... References: <20150224015721.GT74514@kib.kiev.ua> <54EBDC1C.3060007@astrodoggroup.com> <20150224024250.GV74514@kib.kiev.ua> <20150224174053.GG46794@funkthat.com> <54ECBD4B.6000007@freebsd.org> <20150224182507.GI46794@funkthat.com> <54ECEA43.2080008@freebsd.org> <20150224231921.GQ46794@funkthat.com> <20150225002301.GS46794@funkthat.com> In-Reply-To: <20150225002301.GS46794@funkthat.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: Konstantin Belousov , Harrison Grundy , "freebsd-arch@freebsd.org" X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 25 Feb 2015 07:55:21 -0000 On 2/24/15 7:23 PM, John-Mark Gurney wrote: > K. Macy wrote this message on Tue, Feb 24, 2015 at 15:33 -0800: >>> If someone does find a performance issue w/ my patch, I WILL work with >>> them on a solution, but I will not work w/ people who make unfounded >>> claims about the impact of this work... >>> >> ... The concerns may be exaggerated, but they aren't >> unfounded. Not quite the same thing, but no one wants to spend the > Till someone shows me code in the kernel tree where this is even close > to a performance problem, it is unfounded... I've asked, and no one > has > >> cycles doing a SHA256 because it's "The Right Thing"(tm) when their >> use case only requires a fletcher2. > Depends upon what you're doing.. I haven't proposed changing ZFS's > default to sha256, so stop w/ the false equivalences... > >> If it doesn't already exist, it might also be worth looking in to a >> more scalable CSPRNG implementation not requiring locking in the >> common case. For example, each core is seeded separately periodically >> so that has a private pool that is protected by a critical section. >> The private pool would be regularly refreshed by cpu-local callout. >> Thus, a lock would only be acquired if the local entropy were >> depleted. > I'm not discussing this until you read and reply to my original email, > since it's clear that my original email's contents has been ignored in > this thread... > What is final proposal? More spinlocks? That is not a good idea. Doing a single buildworld is not enough. Ask netflix or someone with a real load of 1000s of threads/processing to do testing for you if you truly want to touch scheduler. -Alfred