>>>>> "Andrew" == Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> writes: Andrew> On Fri, 22 Jun 2012 10:24:58 -0400 Andrew> "John Stoffel" <john@xxxxxxxxxxx> wrote: >> >>>>> "Rik" == Rik van Riel <riel@xxxxxxxxxxx> writes: >> Rik> A long time ago, we decided to limit the number of VMAs per Rik> process to 64k. As it turns out, there actually are programs Rik> using tens of thousands of VMAs. >> >> Rik> Performance >> Rik> Testing performance with a benchmark that allocates tens Rik> of thousands of VMAs, unmaps them and mmaps them some more Rik> in a loop, shows promising results. >> >> How are the numbers for applications which only map a few VMAs? Is >> there any impact there? >> Andrew> Johannes did a test for that: https://lkml.org/lkml/2012/6/22/219 I don't see that in his results. But maybe (probably) I don't understand what types of applications this change is supposed to help. I guess I worry that this will just keep slowing down other apps. His tests seemed to be for just one VMA remapped with thousands in use. Or am I missing the fact that all VMAs are in the same pool? Andrew> Some regression with such a workload is unavoidable, I expect. Andrew> We have to work out whether the pros outweigh the cons. This Andrew> involves handwaving. Yup, it does. Proof by vigorous handwaving is a time honored tradition. And I do see that the numbers aren't that much poorer, I just keep thinking that if we can speed up the corner case, can't we also speed up the normal case with a better algorithm or data structure? John -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>