Date: Wed, 25 Feb 2015 09:11:05 -0500 From: Alfred Perlstein <bright@mu.org> To: Konstantin Belousov <kostikbel@gmail.com>, Harrison Grundy <harrison.grundy@astrodoggroup.com> Cc: freebsd-arch@freebsd.org Subject: Re: locks and kernel randomness... Message-ID: <54EDD7F9.9030608@mu.org> In-Reply-To: <20150225085659.GA74514@kib.kiev.ua> References: <DD06E2EA-68D6-43D7-AA17-FB230750E55A@bsdimp.com> <20150224174053.GG46794@funkthat.com> <54ECBD4B.6000007@freebsd.org> <20150224182507.GI46794@funkthat.com> <54ECEA43.2080008@freebsd.org> <20150224231921.GQ46794@funkthat.com> <CAHM0Q_NhUpr_HJZZcAEoZ_hNvZKcVzUBH-7LALsbkgqjLimA7A@mail.gmail.com> <20150225002301.GS46794@funkthat.com> <54ED80BD.1080603@freebsd.org> <54ED87E9.8030706@astrodoggroup.com> <20150225085659.GA74514@kib.kiev.ua>
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On 2/25/15 3:56 AM, Konstantin Belousov wrote: > The cost of the proposed patch, of course, is not the several > thousands of instructions in the rebalance. The problem with it is the > introduction of the new spinlock, which will be used in many places > after the introduction. The cost of the new and often used spinlock is > the increase of both interrupt latency and interrupt handler jitter and > cpu switch jitter. > > So neither buildworld timing, nor network throughput are adequate > to estimate the change. It is system unresponsivness and loss of > the realtime behaviour up to some degree. > > I thought that it was obvious, at least after spinlocks were mentioned, > but apparently it is not, since proposals to measure the patch effect > by benchmarking buildworld or passing the traffic are made. > Thank you. -Alfred
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