linux-kernel - Re: [PATCH 00/11] x86: cleanup early per cpu variables/accesses v5-folded

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Date:	Mon, 28 Apr 2008 15:42:53 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Mike Travis <travis@....com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 00/11] x86: cleanup early per cpu variables/accesses
	v5-folded


* Mike Travis <travis@....com> wrote:

> 1/11:	Increase the limit of NR_CPUS to 4096 and introduce a boolean
> 	called "MAXSMP" which when set (e.g. "allyesconfig"), will set
> 	NR_CPUS = 4096 and NODES_SHIFT = 9 (512).  Changed max setting
> 	for NODES_SHIFT from 15 to 9 to accurately reflect the real limit.
> 
> 2/11:	Introduce a new PER_CPU macro called "EARLY_PER_CPU".  This is
> 	used by some per_cpu variables that are initialized and accessed
> 	before there are per_cpu areas allocated.
> 
> 	Add a flag "arch_provides_topology_pointers" that indicates pointers
> 	to topology cpumask_t maps are available.  Otherwise, use the function
> 	returning the cpumask_t value.  This is useful if cpumask_t set size
> 	is very large to avoid copying data on to/off of the stack.
> 
> 3/11:	Restore the nodenumber field in the x86_64 pda.  This field is slightly
> 	different than the x86_cpu_to_node_map mainly because it's a static
> 	indication of which node the cpu is on while the cpu to node map is a
> 	dyanamic mapping that may get reset if the cpu goes offline.  This also
> 	simplifies the numa_node_id() macro.
> 
> 4/11:	Consolidate node_to_cpumask operations and remove the 256k
> 	byte node_to_cpumask_map.  This is done by allocating the
> 	node_to_cpumask_map array after the number of possible
> 	nodes (nr_node_ids) is known.
> 
> 5/11:	Replace usages of MAX_NUMNODES with nr_node_ids in kernel/sched.c,
> 	where appropriate.  This saves some allocated space as well as many
> 	wasted cycles going through node entries that are non-existent.
> 
> 6/11:	Changed some global definitions in drivers/base/cpu.c to static.
> 
> 7/11:	Remove 544k bytes from the kernel by removing the boot_cpu_pda
> 	array from the data section and allocating it during startup.
> 
> 8/11:	Increase performance for systems with large count NR_CPUS by
> 	limiting the range of the cpumask operators that loop over
> 	the bits in a cpumask_t variable.  This removes a large amount
> 	of wasted cpu cycles.
> 
> 9/11:	Change references from for_each_cpu_mask to for_each_cpu_mask_ptr
> 	in all cases for x86_64 and generic code.
> 
> 10/11:	Change references from next_cpu to next_cpu_nr (or for_each_cpu_mask_ptr
> 	if applicable), in all cases for x86_64 and generic code.
> 
> 11/11:  Pass reference to cpumask variable in net/sunrpc/svc.c

thanks Travis, applied.

	Ingo
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