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Date: Thu, 22 Jan 2009 16:08:15 -0800 From: Jeremy Fitzhardinge <jeremy@...p.org> To: "H. Peter Anvin" <hpa@...or.com> CC: Zachary Amsden <zach@...are.com>, Nick Piggin <npiggin@...e.de>, Ingo Molnar <mingo@...e.hu>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Linus Torvalds <torvalds@...ux-foundation.org>, "jeremy@...source.com" <jeremy@...source.com>, "chrisw@...s-sol.org" <chrisw@...s-sol.org>, "rusty@...tcorp.com.au" <rusty@...tcorp.com.au>, Andrew Morton <akpm@...ux-foundation.org>, Xen-devel <xen-devel@...ts.xensource.com> Subject: Re: lmbench lat_mmap slowdown with CONFIG_PARAVIRT H. Peter Anvin wrote: > Right now a number of the call sites contain a huge push/pop sequence > followed by an indirect call. We can patch in the native code to > avoid the branch overhead, but the register constraints and icache > footprint is unchanged. That's true for the pvops hooks emitted in the .S files, but not so true for ones in C code (well, there are no explicit push/pops, but the presence of the call may cause the compiler to generate them). The .S hooks can definitely be cleaned up, but I don't think that's germane to Nick's observations that the mm code is showing slowdowns. J -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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