Messages in this thread | | | Date | Thu, 18 May 2006 17:26:09 +1000 | From | Nick Piggin <> | Subject | Re: [PATCH] mm: limit lowmem_reserve |
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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.
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