On (25/04/07 23:46), Christoph Lameter didst pronounce: > On Thu, 26 Apr 2007, Nick Piggin wrote: > > > Yeah. IMO anti-fragmentation and defragmentation is the hack, and we > > should stay away from higher order allocations whenever possible. > > Right and we need to create series of other approaches that we then label > "non-hack" to replace it. >
To date, there hasn't been a credible alternative to dealing with fragmentation. Breaking the 1:1 virtual:physical mapping and defragmenting would incur a serious performance hit. > > Hardware is built to handle many small pages efficintly, and I don't > > understand how it could be an SGI-only issue. Sure, you may have an > > order of magnitude or more memory than anyone else, but even my lowly > > desktop _already_ has orders of magnitude more pages than it has TLB > > entries or cache -- if a workload is cache-nice for me, it probably > > will be on a 1TB machine as well, and if it is bad for the 1TB machine, > > it is also bad on mine. > > There have been numbers of people that have argued the same point. Just > because we have developed a way of thinking to defend our traditional 4k > values does not make them right. > > > If this is instead an issue of io path or reclaim efficiency, then it > > would be really nice to see numbers... but I don't think making these > > fundamental paths more complex and slower is a nice way to fix it > > (larger PAGE_SIZE would be, though). > > The code paths can stay the same. You can switch CONFIG_LARGE pages off > if you do not want it and it is as it was. > It may not even need that that much effort. The most stressful use of the high order allocation paths here require the creation of a filesystem and is a deliberate action by the user. > If you would have a look the patches: The code is significantly cleanup > and easier to read. It is easier to read all right and may be worth doing anyway. -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
