linux-kernel - Re: [patch 02/41] cpu alloc: The allocator

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Message-ID: <4846AEF6.2020107@sgi.com>
Date:	Wed, 04 Jun 2008 08:04:22 -0700
From:	Mike Travis <travis@....com>
To:	Rusty Russell <rusty@...tcorp.com.au>
CC:	Christoph Lameter <clameter@....com>, akpm@...ux-foundation.org,
	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>
Subject: Re: [patch 02/41] cpu alloc: The allocator

Rusty Russell wrote:
> On Friday 30 May 2008 13:56:22 Christoph Lameter wrote:
>> The per cpu allocator allows dynamic allocation of memory on all
>> processors simultaneously. A bitmap is used to track used areas.
>> The allocator implements tight packing to reduce the cache footprint
>> and increase speed since cacheline contention is typically not a concern
>> for memory mainly used by a single cpu. Small objects will fill up gaps
>> left by larger allocations that required alignments.
> 
> Allocator seems nice and simple, similar to existing one in module.c (which 
> predates cool bitmap operators).
> 
> Being able to do per-cpu allocations in an interrupt handler seems like 
> encouraging a Bad Idea though: I'd be tempted to avoid the flags word, always 
> zero, and use a mutex instead of a spinlock.
> 
> Cheers,
> Rusty.

I haven't seen any further discussion on these aspects... is there a consensus
to remove the flags from CPU_ALLOC() and use a mutex?

Thanks,
Mike
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