Date: Tue, 16 Jan 2007 15:34:31 -0800 From: "Kip Macy" <kip.macy@gmail.com> To: "Ivan Voras" <ivoras@fer.hr> Cc: freebsd-current@freebsd.org, freebsd-arch@freebsd.org Subject: Re: [PATCH] Mantaining turnstile aligned to 128 bytes in i386 CPUs Message-ID: <b1fa29170701161534n1f6c3803tbb8ca60996d200d9@mail.gmail.com> In-Reply-To: <eojlnb$qje$1@sea.gmane.org> References: <3bbf2fe10607250813w8ff9e34pc505bf290e71758@mail.gmail.com> <3bbf2fe10607251004wf94e238xb5ea7a31c973817f@mail.gmail.com> <3bbf2fe10607261127p3f01a6c3w80027754f7d4e594@mail.gmail.com> <3bbf2fe10607281004o6727e976h19ee7e054876f914@mail.gmail.com> <3bbf2fe10701160851r79b04464m2cbdbb7f644b22b6@mail.gmail.com> <20070116154258.568e1aaf@pleiades.nextvenue.com> <b1fa29170701161355lc021b90o35fa5f9acb5749d@mail.gmail.com> <eoji7s$cit$2@sea.gmane.org> <b1fa29170701161425n7bcfe1e5m1b8c671caf3758db@mail.gmail.com> <eojlnb$qje$1@sea.gmane.org>
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> Maybe even someone finds a way to get optimized versions of memcpy in
> the kernel :)
>
> I was thinking: AFAIK the only major stopper is context saving of the
> various "auxiliary" registers - FPU, MMX, SSE, right? But is it an
> all-or-nothing situation? I.e. does it make sense (can it be done?) to
> just elect to save the MMX context? (AFAIK they are different registers
> than SSE, but overlay FPU registers?) The idea is to save something
> smaller than the full set.
It makes a huge difference in a proprietary file serving appliance
that I know of. However, past measurements on FreeBSD have supposedly
indicated that it isn't that big win as a result of increased context
switch time.
-Kip
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