Date: Tue, 24 Feb 2015 16:23:01 -0800 From: John-Mark Gurney <jmg@funkthat.com> To: "K. Macy" <kmacy@freebsd.org> Cc: Konstantin Belousov <kostikbel@gmail.com>, Harrison Grundy <harrison.grundy@astrodoggroup.com>, Alfred Perlstein <alfred@freebsd.org>, "freebsd-arch@freebsd.org" <freebsd-arch@freebsd.org> Subject: Re: locks and kernel randomness... Message-ID: <20150225002301.GS46794@funkthat.com> In-Reply-To: <CAHM0Q_NhUpr_HJZZcAEoZ_hNvZKcVzUBH-7LALsbkgqjLimA7A@mail.gmail.com> References: <20150224015721.GT74514@kib.kiev.ua> <54EBDC1C.3060007@astrodoggroup.com> <20150224024250.GV74514@kib.kiev.ua> <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>
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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...
> >
>
> <shrug> ... 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...
--
John-Mark Gurney Voice: +1 415 225 5579
"All that I will do, has been done, All that I have, has not."
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