linux-kernel - Re: [patch 03/41] cpu alloc: Use cpu allocator instead of the builtin modules per cpu allocator

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Message-Id: <20080529215837.0528fb3b.akpm@linux-foundation.org>
Date:	Thu, 29 May 2008 21:58:37 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Christoph Lameter <clameter@....com>
Cc:	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
	David Miller <davem@...emloft.net>,
	Eric Dumazet <dada1@...mosbay.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Mike Travis <travis@....com>
Subject: Re: [patch 03/41] cpu alloc: Use cpu allocator instead of the
 builtin modules per cpu allocator

On Thu, 29 May 2008 20:56:23 -0700 Christoph Lameter <clameter@....com> wrote:

> Remove the builtin per cpu allocator from modules.c and use cpu_alloc instead.
> 
> The patch also removes PERCPU_ENOUGH_ROOM. The size of the cpu_alloc area is
> determined by CONFIG_CPU_AREA_SIZE. PERCPU_ENOUGH_ROOMs default was 8k.
> CONFIG_CPU_AREA_SIZE defaults to 30k. Thus we have more space to load modules.
> 
>
> ...
>
> +		unsigned long align = sechdrs[pcpuindex].sh_addralign;
> +		unsigned long size = sechdrs[pcpuindex].sh_size;
> +
> +		if (align > PAGE_SIZE) {
> +			printk(KERN_WARNING "%s: per-cpu alignment %li > %li\n",
> +			mod->name, align, PAGE_SIZE);

Indenting broke.

Alas, PAGE_SIZE has, iirc, unsigned type on some architectures and
unsigned long on others.  I suspect you'll need to cast it to be able
to print it.

> +			align = PAGE_SIZE;
> +		}
> +		percpu = cpu_alloc(size, GFP_KERNEL|__GFP_ZERO, align);
> +		if (!percpu)
> +			printk(KERN_WARNING "Could not allocate %lu bytes percpu data\n",

80-col bustage,.

A printk like this should, I think, identify what part of the kernel it
came from.

But really, I don't think any printk should be present here. 
cpu_alloc() itself should dump the warning and the backtrace when it
runs out.  Because a cpu_alloc() failure is a major catastrophe.  It
probably means a reconfigure-and-reboot cycle.

Right now it means a
reconfigure-kernel-rebuild-kernel-reinstall-kernel-then-reboot cycle. 
Or a call-vendor-complain-pay-money-and-wait cycle.  But I hope we can
fix that with the boot parameter thing?


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