Messages in this thread | | | Date | Mon, 30 Sep 2013 08:27:49 -0700 | From | Dave Hansen <> | Subject | Re: [PATCHv6 00/22] Transparent huge page cache: phase 1, everything but mmap() |
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On 09/30/2013 03:02 AM, Mel Gorman wrote: > I am afraid I never looked too closely once I learned that the primary > motivation for this was relieving iTLB pressure in a very specific > case. AFAIK, this is not a problem in the vast majority of modern CPUs > and I found it very hard to be motivated to review the series as a result. > I suspected that in many cases that the cost of IO would continue to dominate > performance instead of TLB pressure. I also found it unlikely that there > was a workload that was tmpfs based that used enough memory to be hurt > by TLB pressure. My feedback was that a much more compelling case for the > series was needed but this discussion all happened on IRC unfortunately.
FWIW, I'm mostly intrigued by the possibilities of how this can speed up _software_, and I'm rather uninterested in what it can do for the TLB. Page cache is particularly painful today, precisely because hugetlbfs and anonymous-thp aren't available there. If you have an app with hundreds of GB of files that it wants to mmap(), even if it's in the page cache, it takes _minutes_ to just fault in. One example:
https://lkml.org/lkml/2013/6/27/698
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