Date: Sun, 29 Nov 2009 16:06:02 -0800 From: Julian Elischer <julian@elischer.org> To: Scott Long <scottl@samsco.org> Cc: Attilio Rao <attilio@freebsd.org>, arch@freebsd.org Subject: Re: sglist(9) Message-ID: <4B130C6A.70406@elischer.org> In-Reply-To: <66707B0F-D0AB-49DB-802F-13146F488E1A@samsco.org> References: <200905191458.50764.jhb@freebsd.org> <alpine.BSF.2.00.0905200841230.981@desktop> <200905201522.58501.jhb@freebsd.org> <3bbf2fe10911291429k54b4b7cfw9e40aefeca597307@mail.gmail.com> <66707B0F-D0AB-49DB-802F-13146F488E1A@samsco.org>
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Scott Long wrote: > I think this is fundamentally wrong. You're proposing exchanging a > cheap operation of splitting VA's with an expensive operation of > allocating, splitting, copying, and refcounting sglists. Splitting is > an excessively common operation, and your proposal will impact > performance as storage becomes exponentially faster. > From the perspective of a flashdrive driver the more efficient the better. The current generation of devices are doing 800MB/sec (6.4Gb/sec) of scattter-gather random IO and really that will only go up. We are doing over 130,000 independent transactions per second and we can put multiple drives in a single machine. These numbers will only increase with future developments.
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