From 30bb9811856f667042e746d8033883b1091a46ce Mon Sep 17 00:00:00 2001 From: Andi Kleen Date: Tue, 14 Nov 2017 07:42:56 -0500 Subject: x86/topology: Avoid wasting 128k for package id array Analyzing large early boot allocations unveiled the logical package id storage as a prominent memory waste. Since commit 1f12e32f4cd5 ("x86/topology: Create logical package id") every 64-bit system allocates a 128k array to convert logical package ids. This happens because the array is sized for MAX_LOCAL_APIC which is always 32k on 64bit systems, and it needs 4 bytes for each entry. This is fairly wasteful, especially for the common case of having only one socket, which uses exactly 4 byte out of 128K. There is no user of the package id map which is performance critical, so the lookup is not required to be O(1). Store the logical processor id in cpu_data and use a loop based lookup. To keep the mapping stable accross cpu hotplug operations, add a flag to cpu_data which is set when the CPU is brought up the first time. When the flag is set, then cpu_data is not reinitialized by copying boot_cpu_data on subsequent bringups. [ tglx: Rename the flag to 'initialized', use proper pointers instead of repeated cpu_data(x) evaluation and massage changelog. ] Signed-off-by: Andi Kleen Signed-off-by: Prarit Bhargava Signed-off-by: Thomas Gleixner Cc: Tom Lendacky Cc: Christian Borntraeger Cc: Peter Zijlstra Cc: Kan Liang Cc: He Chen Cc: Stephane Eranian Cc: Dave Hansen Cc: Piotr Luc Cc: Andy Lutomirski Cc: Arvind Yadav Cc: Vitaly Kuznetsov Cc: Borislav Petkov Cc: Tim Chen Cc: Mathias Krause Cc: "Kirill A. Shutemov" Link: https://lkml.kernel.org/r/20171114124257.22013-3-prarit@redhat.com --- arch/x86/include/asm/processor.h | 1 + 1 file changed, 1 insertion(+) (limited to 'arch/x86/include') diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 2db7cf720b04..cc16fa882e3e 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -132,6 +132,7 @@ struct cpuinfo_x86 { /* Index into per_cpu list: */ u16 cpu_index; u32 microcode; + unsigned initialized : 1; } __randomize_layout; struct cpuid_regs { -- cgit v1.2.3