David Mosberger-Tang wrote on Wednesday, November 02, 2005 10:59 AM > On 11/2/05, Robin Holt <holt@sgi.com> wrote: > > > Does anybody have any objections to making 4 level the default? > > My concern is that 4-level PT really isn't needed on ia64 for all but > the largest machines No kidding. People envy that I have a machine with 64 GB, 128 GB and I envy Robin has access to machine with more than 16 TB. How many average joe is going to be able to afford machine like that? Actually, how many installation will there be in the entire world (100?, 1000?) > so perhaps it's not a bad idea to make 4-level the > default and see if anyone complains about performance regressions. He he. What a nice way to kick people around for doing performance measurement :-) I just did a quick measurement with I/O submission path. get_user_pages is my biggest concern that extra level means more code and cache foot print for each I/O submission. It cost about 1.5% more in I/O path length on a micro-benchmark (from block layer and Up). This could be all buried as noise in a larger scheme for industry database benchmark. Another thing: has people tested 4 level page table with 4GB hugetlb page size? Looks like pud is already falling short on bits and entire pgd bits will be falling off the 64-bit. 128-bit computing anybody? (just kidding). - Ken - To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.htmlReceived on Thu Nov 03 12:54:23 2005
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