From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nikita Danilov MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <18125.23918.550443.628936@gargle.gargle.HOWL> Date: Thu, 23 Aug 2007 14:11:58 +0400 Subject: Re: [RFC 2/9] Use NOMEMALLOC reclaim to allow reclaim if PF_MEMALLOC is set In-Reply-To: <1187861208.6114.342.camel@twins> References: <20070814153021.446917377@sgi.com> <20070814153501.305923060@sgi.com> <20070818071035.GA4667@ucw.cz> <1187641056.5337.32.camel@lappy> <1187644449.5337.48.camel@lappy> <20070821003922.GD8414@wotan.suse.de> <1187705235.6114.247.camel@twins> <20070823033826.GE18788@wotan.suse.de> <1187861208.6114.342.camel@twins> Sender: owner-linux-mm@kvack.org Return-Path: To: Peter Zijlstra Cc: Nick Piggin , Christoph Lameter , Pavel Machek , linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, dkegel@google.com, David Miller List-ID: Peter Zijlstra writes: [...] > My idea is to extend kswapd, run cpus_per_node instances of kswapd per > node for each of GFP_KERNEL, GFP_NOFS, GFP_NOIO. (basically 3 kswapds > per cpu) > > whenever we would hit direct reclaim, add ourselves to a special > waitqueue corresponding to the type of GFP and kick all the > corresponding kswapds. There are two standard objections to this: - direct reclaim was introduced to reduce memory allocation latency, and going to scheduler kills this. But more importantly, - it might so happen that _all_ per-cpu kswapd instances are blocked, e.g., waiting for IO on indirect blocks, or queue congestion. In that case whole system stops waiting for IO to complete. In the direct reclaim case, other threads can continue zone scanning. Nikita. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org