Hi David, On 07.03.2011 [15:47:23 -0800], David Rientjes wrote: > On Mon, 7 Mar 2011, Andrew Morton wrote: > > > > > > On Mon, 2011-03-07 at 14:05 +0100, Petr Holasek wrote: > > > > > > + for_each_hstate(h) > > > > > > + seq_printf(m, > > > > > > + "HugePages_Total: %5lu\n" > > > > > > + "HugePages_Free: %5lu\n" > > > > > > + "HugePages_Rsvd: %5lu\n" > > > > > > + "HugePages_Surp: %5lu\n" > > > > > > + "Hugepagesize: %8lu kB\n", > > > > > > + h->nr_huge_pages, > > > > > > + h->free_huge_pages, > > > > > > + h->resv_huge_pages, > > > > > > + h->surplus_huge_pages, > > > > > > + 1UL << (huge_page_order(h) + PAGE_SHIFT - 10)); > > > > > > } > > > > > > > > > > It sounds like now we'll get a meminfo that looks like: > > > > > > > > > > ... > > > > > AnonHugePages: 491520 kB > > > > > HugePages_Total: 5 > > > > > HugePages_Free: 2 > > > > > HugePages_Rsvd: 3 > > > > > HugePages_Surp: 1 > > > > > Hugepagesize: 2048 kB > > > > > HugePages_Total: 2 > > > > > HugePages_Free: 1 > > > > > HugePages_Rsvd: 1 > > > > > HugePages_Surp: 1 > > > > > Hugepagesize: 1048576 kB > > > > > DirectMap4k: 12160 kB > > > > > DirectMap2M: 2082816 kB > > > > > DirectMap1G: 2097152 kB > > > > > > > > > > At best, that's a bit confusing. There aren't any other entries in > > > > > meminfo that occur more than once. Plus, this information is available > > > > > in the sysfs interface. Why isn't that sufficient? > > > > > > > > > > Could we do something where we keep the default hpage_size looking like > > > > > it does now, but append the size explicitly for the new entries? > > > > > > > > > > HugePages_Total(1G): 2 > > > > > HugePages_Free(1G): 1 > > > > > HugePages_Rsvd(1G): 1 > > > > > HugePages_Surp(1G): 1 > > > > > > > > > > > > > Let's not change the existing interface, please. > > > > > > > > Adding new fields: OK. > > > > Changing the way in whcih existing fields are calculated: OKish. > > > > Renaming existing fields: not OK. > > > > > > How about lining up multiple values in each field like this? > > > > > > HugePages_Total: 5 2 > > > HugePages_Free: 2 1 > > > HugePages_Rsvd: 3 1 > > > HugePages_Surp: 1 1 > > > Hugepagesize: 2048 1048576 kB > > > ... > > > > > > This doesn't change the field names and the impact for user space > > > is still small? > > > > It might break some existing parsers, dunno. > > > > It was a mistake to assume that all hugepages will have the same size > > for all time, and we just have to live with that mistake. > > > > I'm not sure it was a mistake: the kernel has a default hugepage size and > that's what the global /proc/sys/vm/nr_hugepages tunable uses, so it seems > appropriate that its statistics are exported in the global /proc/meminfo. Yep, the intent was for meminfo to (continue to) document the default hugepage size's usage, and for any other size's statistics to be accessed by the appropriate sysfs entries. > > I'd suggest that we leave meminfo alone, just ensuring that its output > > makes some sense. Instead create a new interface which presents all > > the required info in a sensible fashion and migrate usersapce reporting > > tools over to that interface. Just let the meminfo field die a slow > > death. > > > > (Adding Nishanth to the cc) > > It's already there, all this data is available for all the configured > hugepage sizes via /sys/kernel/mm/hugepages/hugepages-<size>kB/ as > described by Documentation/ABI/testing/sysfs-kernel-mm-hugepages. > > It looks like Nishanth and others put quite a bit of effort into > making as stable of an API as possible for this information. I'm not sure if libhugetlbfs already has a tool for parsing the values there (i.e., to give an end-user a quick'n'dirty snapshot of overall current hugepage usage). Eric? If not, probably something worth having. I believe we also have the per-node information in sysfs too, in case that's relevant to tooling. Thanks, Nish -- Nishanth Aravamudan <nacc@xxxxxxxxxx> IBM Linux Technology Center -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>