Messages in this thread | | | Date | Fri, 2 Mar 2007 12:59:33 -0800 | From | Bill Irwin <> | Subject | Re: The performance and behaviour of the anti-fragmentation related patches |
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On Fri, 02 Mar 2007 12:43:42 -0500 Rik van Riel <riel@redhat.com> wrote: >> I can't share all the details, since a lot of the problems are customer >> workloads. >> One particular case is a 32GB system with a database that takes most >> of memory. The amount of actually freeable page cache memory is in >> the hundreds of MB.
On Fri, Mar 02, 2007 at 10:06:19AM -0800, Andrew Morton wrote: > Where's the rest of the memory? tmpfs? mlocked? hugetlb?
I know of one sounding similar to this where unreclaimable pages are pinned by refcounts held by bio's spread across about 850 spindles. It's mostly read traffic. Several different tunables could be used to work around it, nr_requests in particular, but also clamping down on dirty limits to preposterously low levels and setting preposterously large values of min_free_kbytes. Their kernel is, of course, substantially downrev (2.6.9-based IIRC), so douse things heavily with grains of salt.
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