From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <446C2191.70300@yahoo.com.au> Date: Thu, 18 May 2006 17:26:09 +1000 From: Nick Piggin MIME-Version: 1.0 Subject: Re: [PATCH] mm: limit lowmem_reserve References: <200604021401.13331.kernel@kolivas.org> <200605180011.43216.kernel@kolivas.org> <446C1E25.4080408@yahoo.com.au> <200605181721.38735.kernel@kolivas.org> In-Reply-To: <200605181721.38735.kernel@kolivas.org> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Con Kolivas Cc: Andrew Morton , ck@vds.kolivas.org, linux list , linux-mm@kvack.org List-ID: Con Kolivas wrote: > On Thursday 18 May 2006 17:11, Nick Piggin wrote: > >>If we're under memory pressure, kswapd will try to free up any candidate >>zone, yes. >> >> >>>On my test case this indeed happens and my ZONE_DMA never goes below 3000 >>>pages free. If I lower the reserve even further my pages free gets stuck >>>at 3208 and can't free any more, and doesn't ever drop below that either. >>> >>>Here is the patch I was proposing >> >>What problem does that fix though? > > > It's a generic concern and I honestly don't know how significant it is which > is why I'm asking if it needs attention. That concern being that any time > we're under any sort of memory pressure, ZONE_DMA will undergo intense > reclaim even though there may not really be anything specifically going on in > ZONE_DMA. It just seems a waste of cycles doing that. > If it doesn't have any/much pagecache or slab cache in it, there won't be intense reclaim; if it does then it can be reclaimed and the memory used. reclaim / allocation could be slightly smarter about scaling watermarks, however I don't think it is much of an issue at the moment. -- SUSE Labs, Novell Inc. Send instant messages to your online friends http://au.messenger.yahoo.com -- 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