Date: Fri, 27 Mar 2015 17:43:56 -0400 From: Eric van Gyzen <vangyzen@FreeBSD.org> To: Rui Paulo <rpaulo@me.com> Cc: current@FreeBSD.org Subject: Re: SSE in libthr Message-ID: <5515CF1C.8010409@FreeBSD.org> In-Reply-To: <3A96AAEC-9C1C-444E-9A73-3CD2AED33116@me.com> References: <5515AED9.8040408@FreeBSD.org> <3A96AAEC-9C1C-444E-9A73-3CD2AED33116@me.com>
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On 03/27/2015 16:49, Rui Paulo wrote: > > Regarding your patch, I think we should disable even more, if possible. How about: > > CFLAGS+= -mno-mmx -mno-3dnow -mno-sse -mno-sse2 -mno-sse3 Yes, I was considering copying all of the similar flags that we use in the kernel. That seems wise. According to comments in sys/conf/kern.mk, only no-mmx and no-sse would be necessary, as they imply the others. dim@ raised the possibility of CPUTYPE=foo on i386, so I would also apply this change to i386. An updated patch is below. Eric Index: base/head/lib/libthr/arch/amd64/Makefile.inc =================================================================== --- base/head/lib/libthr/arch/amd64/Makefile.inc (revision 280703) +++ base/head/lib/libthr/arch/amd64/Makefile.inc (working copy) @@ -1,3 +1,8 @@ #$FreeBSD$ SRCS+= _umtx_op_err.S + +# Using SSE incurs extra overhead per context switch, +# which measurably impacts performance when the application +# does not otherwise use FP/SSE. +CFLAGS+=-mno-sse -mno-mmx Index: base/head/lib/libthr/arch/i386/Makefile.inc =================================================================== --- base/head/lib/libthr/arch/i386/Makefile.inc (revision 280703) +++ base/head/lib/libthr/arch/i386/Makefile.inc (working copy) @@ -1,3 +1,8 @@ # $FreeBSD$ SRCS+= _umtx_op_err.S + +# Using SSE incurs extra overhead per context switch, +# which measurably impacts performance when the application +# does not otherwise use FP/SSE. +CFLAGS+=-mno-sse -mno-mmx
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