Messages in this thread | | | Date | Thu, 3 Jul 2003 11:53:41 -0700 | From | William Lee Irwin III <> | Subject | Re: What to expect with the 2.6 VM |
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On Thu, 3 Jul 2003, Andrea Arcangeli wrote: >> even if you don't use largepages as you should, the ram cost of the pte >> is nothing on 64bit archs, all you care about is to use all the mhz and >> tlb entries of the cpu.
On Thu, Jul 03, 2003 at 09:06:32AM -0400, Rik van Riel wrote: > That depends on the number of Oracle processes you have. > Say that page tables need 0.1% of the space of the virtual > space they map. With 1000 Oracle users you'd end up needing > as much memory in page tables as your shm segment is large. > Of course, in this situation either the application should > use large pages or the kernel should simply reclaim the > page tables (possible while holding the mmap_sem for write).
No, it is not true that pagetable space can be wantonly wasted on 64-bit.
Try mmap()'ing something sufficiently huge and accessing on average every PAGE_SIZE'th virtual page, in a single-threaded single process. e.g. various indexing schemes might do this. This is 1 pagetable page per page of data (worse if shared), which blows major goats.
There's a reason why those things use inverted pagetables... at any rate, compacting virtualspace with remap_file_pages() solves it too.
Large pages won't help, since the data isn't contiguous.
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