Wrong Vmalloc numbers in /proc/meminfo

Frans Pop

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Sep 27, 2009, 8:10:04 PM9/27/09

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With 2.6.31 (on x86_64) I'm seeing the following in /proc/meminfo.

$ cat /proc/meminfo
MemTotal: 2030968 kB
MemFree: 539408 kB
Buffers: 94984 kB
Cached: 308564 kB
SwapCached: 16048 kB
Active: 652236 kB
Inactive: 428808 kB
Active(anon): 436808 kB
Inactive(anon): 246996 kB
Active(file): 215428 kB
Inactive(file): 181812 kB
Unevictable: 1632 kB
Mlocked: 1632 kB
SwapTotal: 2097144 kB
SwapFree: 1979524 kB
Dirty: 12 kB
Writeback: 0 kB
AnonPages: 671276 kB
Mapped: 57684 kB
Slab: 177692 kB
SReclaimable: 160516 kB
SUnreclaim: 17176 kB
PageTables: 14812 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 3112628 kB
Committed_AS: 988780 kB
VmallocTotal: 34359738367 kB
VmallocUsed: 340084 kB
VmallocChunk: 34359387131 kB
DirectMap4k: 2008768 kB
DirectMap2M: 63488 kB

Is it me or are VmallocTotal and VmallocChunk off by a factor 10,000 or so?

Cheers,
FJP
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KAMEZAWA Hiroyuki

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Sep 27, 2009, 10:40:05 PM9/27/09

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I'm sorry I misunderstand your 10,000 implies.

On my x86-64 box.
VmallocTotal: 34359738367 kB
VmallocUsed: 100856 kB
VmallocChunk: 34359583863 kB

Then,
34359738367 - 34359583863
154504

Then difference is 13412 (pages)

Hmm. in /proc/vmallocinfo
==
..
0xffffc9000652b000-0xffffc9000672c000 2101248 sys_swapon+0x6a2/0xcd0 pages=512 vmalloc N0=512
0xffffc90007efd000-0xffffc90008dde000 15601664 pcpu_alloc+0x3ad/0x4e0 vmalloc
0xffffc900096d9000-0xffffc900096dd000 16384 e1000e_setup_tx_resources+0x39/0xe0 [e1000e] pages=3 vmalloc N0=3
0xffffc900096de000-0xffffc900096e2000 16384 e1000e_setup_rx_resources+0x37/0x160 [e1000e] pages=3 vmalloc N0=3
==

It seems some amount of memory holes (rather than PAGESIZE) between vmalloc area
info.(especially around pcpu_alloc..) please check /proc/vmallocinfo if you
feel something strange.

Thanks,
-Kame

Frans Pop

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Sep 28, 2009, 1:00:16 PM9/28/09

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On Monday 28 September 2009, KAMEZAWA Hiroyuki wrote:
> > VmallocTotal: 34359738367 kB
> > VmallocUsed: 340084 kB
> > VmallocChunk: 34359387131 kB
> >

> > Is it me or are VmallocTotal and VmallocChunk off by a factor 10,000
> > or so?
>
> I'm sorry I misunderstand your 10,000 implies.

What I meant is: is the Vmalloc area really 32 *terra*bytes in size?
Seems rather big for a system with only 2GB RAM.

I'd never noticed it before and it looks strange to me, but I guess it's
just the result of having 64-bit addressing: a theoretically addressable
area most of which will never actually be used?

KAMEZAWA Hiroyuki

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Sep 28, 2009, 8:10:07 PM9/28/09

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On Mon, 28 Sep 2009 18:56:08 +0200
Frans Pop <ele...@planet.nl> wrote:

> On Monday 28 September 2009, KAMEZAWA Hiroyuki wrote:
> > > VmallocTotal: 34359738367 kB
> > > VmallocUsed: 340084 kB
> > > VmallocChunk: 34359387131 kB
> > >
> > > Is it me or are VmallocTotal and VmallocChunk off by a factor 10,000
> > > or so?
> >
> > I'm sorry I misunderstand your 10,000 implies.
>
> What I meant is: is the Vmalloc area really 32 *terra*bytes in size?
> Seems rather big for a system with only 2GB RAM.
>

VmallocTotal means "available address space size for VMALLOC"
It's fixed size as VMALLOC_END - VMALLOC_START.
VmallocChunk just means "free space in VMALLOC area".
Both of them are not related to size of RAM.

> I'd never noticed it before and it looks strange to me, but I guess it's
> just the result of having 64-bit addressing: a theoretically addressable
> area most of which will never actually be used?
>

you're right. Most of space will never used.

Regards,
-Kame