From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Walrond Subject: Re: No swap can be dangerous (was Re: swap on RAID (was Re: swp - Re: ext3 journal on software raid)) Date: Thu, 6 Jan 2005 22:08:39 +0000 Message-ID: <200501062208.39563.andrew@walrond.org> References: <41DC9420.5030701@h3c.com> <20050106093811.GB99565@caffreys.strugglers.net> <41DD798F.8030902@h3c.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <41DD798F.8030902@h3c.com> Content-Disposition: inline Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org Cc: linux-kernel@vger.kernel.org List-Id: linux-raid.ids On Thursday 06 January 2005 17:46, Mike Hardy wrote: > > You are correct that I was getting at the zero swap argument - and I > agree that it is vastly different from simply not expecting it. It is > important to know that there is no inherent need for swap in the kernel > though - it is simply used as more "memory" (albeit slower, and with > some optimizations to work better with real memory) and if you don't > need it, you don't need it. > If I recollect a recent thread on LKML correctly, your 'no inherent need for swap' might be wrong. I think the gist was this: the kernel can sometimes needs to move bits of memory in order to free up dma-able ram, or lowmem. If I recall correctly, the kernel can only do this move via swap, even if there is stacks of free (non-dmaable or highmem) memory. I distinctly remember the moral of the thread being "Always mount some swap, if you can" This might have changed though, or I might have got it completely wrong. - I've cc'ed LKML incase somebody more knowledgeable can comment... Andrew Walrond