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Message-Id: <200704191354.52985.ak@suse.de> Date: Thu, 19 Apr 2007 13:54:52 +0200 From: Andi Kleen <ak@...e.de> To: discuss@...-64.org Cc: linux-kernel@...r.kernel.org, Arjan van de Ven <arjan@...ux.intel.com> Subject: Dropping CONFIG_REORDER on x86-64 for 2.6.22 Hallo, I'm thinking about dropping the x86-64 CONFIG_REORDER for 2.6.22. The function enabled -ffunction-sections and then tries to reorder the executable While that's in theory a worthy goal to save TLB/icache, in practice it didn't really work out. Rationale: - It cannot be enabled in normal builds because all current lds become very slow when they have to handle thousands of sections. - The list of hot functions it needs - arch/x86_64/kernel/functionlist - hasn't been changed for a long time and is already out of date. I also don't know no sane way to keep it uptodate. Profile feedback at runtime is not practical for the kernel and even if it's questionable we would find a good training workload. Trying to change the manually is imho foolish and likely not too useful anyways (if any hot function is missed the TLB savings will be lost and it is unlikely we can get 100% coverage) - The workloads of the kernel are too diverse to make this concept really work So I'm planning to drop the option and arch/x86_64/kernel/functionlist Comments? -Andi - 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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