On 03/08/2011 12:25 AM, Andrew Morton wrote:
On Tue, 8 Mar 2011 08:14:49 +0900
Naoya Horiguchi<n-horiguchi@xxxxxxxxxxxxx> wrote:
On Mon, Mar 07, 2011 at 02:51:49PM -0800, Andrew Morton wrote:
On Mon, 07 Mar 2011 11:46:54 -0800
Dave Hansen<dave@xxxxxxxxxxxxxxxxxx> 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'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.
The main idea behind this patch is to unify hugetlb interfaces in
/proc/meminfo
and sysfs. When somebody wants to find out all important informations
about hugepage
pools (as hugeadm from libhugetlbfs does), he has to determine default
hugepage size
from /proc/meminfo and then go into
/sys/kernel/mm/hugepages/hugepages-<size>kB/
for informations about next nodes.
I agree with idea of throwing away of meminfo hugepage fields in the future,
but before doing this, sysfs part of interface should indicate default
hugepage
size. And meminfo could possibly show data for all hugepage sizes on
system. So when
these parts will be independent, it is no problem to let meminfo fields
die.
It's tempting to remove the meminfo hugepage fields altogether - most
parsers _should_ be able to cope with a CONFIG_HUGETLB=n kernel. But
that's breakage as well - some applications may be using meminfo to
detect whether the kernel supports huge pages!
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