From: Vlad Zolotarov Date: Mon, 11 Jun 2012 09:56:52 +0000 (+0300) Subject: x86: Add read_mostly declaration/definition to variables from smp.h X-Git-Tag: v3.6-rc1~89^2~10 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0816b0f0365539c8f6280634d2c1778d0108d8f5;p=pandora-kernel.git x86: Add read_mostly declaration/definition to variables from smp.h Add "read-mostly" qualifier to the following variables in smp.h: - cpu_sibling_map - cpu_core_map - cpu_llc_shared_map - cpu_llc_id - cpu_number - x86_cpu_to_apicid - x86_bios_cpu_apicid - x86_cpu_to_logical_apicid As long as all the variables above are only written during the initialization, this change is meant to prevent the false sharing. More specifically, on vSMP Foundation platform x86_cpu_to_apicid shared the same internode_cache_line with frequently written lapic_events. From the analysis of the first 33 per_cpu variables out of 219 (memories they describe, to be more specific) the 8 have read_mostly nature (tlb_vector_offset, cpu_loops_per_jiffy, xen_debug_irq, etc.) and 25 are frequently written (irq_stack_union, gdt_page, exception_stacks, idt_desc, etc.). Assuming that the spread of the rest of the per_cpu variables is similar, identifying the read mostly memories will make more sense in terms of long-term code maintenance comparing to identifying frequently written memories. Signed-off-by: Vlad Zolotarov Acked-by: Shai Fultheim Cc: Shai Fultheim (Shai@ScaleMP.com) Cc: ido@wizery.com Cc: Linus Torvalds Cc: Andrew Morton Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/1719258.EYKzE4Zbq5@vlad Signed-off-by: Ingo Molnar --- Reading git-diff-tree failed