Messages in this thread | | | Date | Thu, 25 Feb 2010 10:00:46 -0500 | From | Rik van Riel <> | Subject | Re: [PATCH 05/15] readahead: limit readahead size for small memory systems |
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On 02/23/2010 10:10 PM, Wu Fengguang wrote: > When lifting the default readahead size from 128KB to 512KB, > make sure it won't add memory pressure to small memory systems. > > For read-ahead, the memory pressure is mainly readahead buffers consumed > by too many concurrent streams. The context readahead can adapt > readahead size to thrashing threshold well. So in principle we don't > need to adapt the default _max_ read-ahead size to memory pressure. > > For read-around, the memory pressure is mainly read-around misses on > executables/libraries. Which could be reduced by scaling down > read-around size on fast "reclaim passes". > > This patch presents a straightforward solution: to limit default > readahead size proportional to available system memory, ie. > 512MB mem => 512KB readahead size > 128MB mem => 128KB readahead size > 32MB mem => 32KB readahead size (minimal) > > Strictly speaking, only read-around size has to be limited. However we > don't bother to seperate read-around size from read-ahead size for now. > > CC: Matt Mackall<mpm@selenic.com> > Signed-off-by: Wu Fengguang<fengguang.wu@intel.com>
Acked-by: Rik van Riel <riel@redhat.com>
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