[PATCH] Auto size the per cpu area. (ba4d40bb) · Commits · 戴 / test

Now for a completely different but trivial approach. I just boot tested it with 255 CPUS and everything worked. Currently everything (except module data) we place in the per cpu area we know about at compile time. So instead of allocating a fixed size for the per_cpu area allocate the number of bytes we need plus a fixed constant for to be used for modules. It isn't perfect but it is much less of a pain to work with than what we are doing now. AK: fixed warning Signed-off-by:

Eric W. Biederman <ebiederm@xmission.com> Signed-off-by:

Andi Kleen <ak@suse.de>

arch/x86_64/kernel/setup64.c

+2 −5

Original line number	Diff line number	Diff line
		@@ -95,12 +95,9 @@ void __init setup_per_cpu_areas(void)
		#endif

		/* Copy section for each CPU (we discard the original) */
		size = ALIGN(__per_cpu_end - __per_cpu_start, SMP_CACHE_BYTES);
		#ifdef CONFIG_MODULES
		if (size < PERCPU_ENOUGH_ROOM)
		size = PERCPU_ENOUGH_ROOM;
		#endif

		printk(KERN_INFO "PERCPU: Allocating %lu bytes of per cpu data\n", size);
		for_each_cpu_mask (i, cpu_possible_map) {
		char *ptr;

include/asm-x86_64/percpu.h

+10 −0

Original line number	Diff line number	Diff line
		@@ -11,6 +11,16 @@

		#include <asm/pda.h>

		#ifdef CONFIG_MODULES
		# define PERCPU_MODULE_RESERVE 8192
		#else
		# define PERCPU_MODULE_RESERVE 0
		#endif

		#define PERCPU_ENOUGH_ROOM \
		(ALIGN(__per_cpu_end - __per_cpu_start, SMP_CACHE_BYTES) + \
		PERCPU_MODULE_RESERVE)

		#define __per_cpu_offset(cpu) (cpu_pda(cpu)->data_offset)
		#define __my_cpu_offset() read_pda(data_offset)

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