From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Thu, 16 Jun 2005 21:45:18 -0700 From: Andrew Morton Subject: Re: Global spinlock vs local bit spin locks Message-Id: <20050616214518.7df96d8a.akpm@osdl.org> In-Reply-To: <1118982092.5261.44.camel@npiggin-nld.site> References: <1118982092.5261.44.camel@npiggin-nld.site> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit To: Nick Piggin Cc: davem@davemloft.net, anton@samba.org, linux-arch@vger.kernel.org, Peter.Keilty@hp.com List-ID: Nick Piggin wrote: > > Peter Keilty is running into some scalability problems with buffer > head based IO. There are a couple of global spinlocks in the buffer > completion path, and they're showing up on 16-way IA64 systems. Well in -mm these spinlocks are hashed and the performance is good. But it's a bit dorky. So we don't _have_ to go with the bit_spin_lock() approach. But bit_spin_lock() is nicer. The reason why I went with a hashed lock is that I have memories of being beaten up over suckiness of bit_spin_lock(). But I'm now wondering who was beating me up, and why ;)