Date: Thu, 01 Jun 2006 09:30:16 +0200 From: Alexander Leidinger <Alexander@Leidinger.net> To: Attilio Rao <asmrookie@gmail.com> Cc: freebsd-hackers@freebsd.org, Suleiman Souhlal <ssouhlal@freebsd.org>, freebsd-arch@freebsd.org Subject: Re: [patch] Adding optimized kernel copying support - Part III Message-ID: <20060601093016.ygeptkv80840gkww@netchild.homeip.net> In-Reply-To: <3bbf2fe10605311632w58c2949buc072e58ac103d7d@mail.gmail.com> References: <3bbf2fe10605311156p7e629283r34d22b368877582d@mail.gmail.com> <447DFA0C.20207@FreeBSD.org> <3bbf2fe10605311329h7adc1722j9088253515e0265b@mail.gmail.com> <20060601084052.D32549@delplex.bde.org> <3bbf2fe10605311632w58c2949buc072e58ac103d7d@mail.gmail.com>
next in thread | previous in thread | raw e-mail | index | archive | help
Quoting Attilio Rao <asmrookie@gmail.com> (from Thu, 1 Jun 2006 =20 01:32:12 +0200): > 2006/6/1, Bruce Evans <bde@zeta.org.au>: >> The new code wouldn't behave much differently under SMP. It just might >> be a smaller optimization because more memory pressure for SMP causes >> more cache misses for everything and there are no benefits from copying >> through MMX/XMM unless nontemporal writes are used. All (?) CPUs with >> MMX or SSE* can saturate main memory using 32-bit instructions. On >> 32-bit CPUs, the benefits of using MMX/XMM come from being able to >> saturate the L1 cache on some CPUs (mainly Athlons and not P[2-4]), >> and from being able to use nontemporal writes on some CPUs (at least >> AthlonXP via SSE extensions all CPUs with SSE2). > > I was just speaking about the copying routine itself and not about the > SSE2 environment preserving mechanism. It remains untouched in SMP > case. AFAIR the DFly FPU rework allows to use FPU/XMM instructions in their =20 kernel without the need to do some manual state preserving (it's done =20 automatically on demand). So one could use XMM instructions in RAID 5 =20 or crypto parts of the code to test if it is a performance benefit. Do =20 I understand the above part right that with this patch this is also =20 the case for us in the UP case, but not in the SMP case? Bye, Alexander. --=20 Selling GoodYear Eagle F1 235/40ZR18, 2x 4mm + 2x 5mm, ~150 EUR you have to pick it up between Germany/Saarland and Luxembourg/Capellen http://www.Leidinger.net Alexander @ Leidinger.net: PGP ID =3D B0063FE7 http://www.FreeBSD.org netchild @ FreeBSD.org : PGP ID =3D 72077137
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20060601093016.ygeptkv80840gkww>