From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To: Tobias Diedrich <ranma+xen@tdiedrich.de>,
xen-users@lists.xensource.com, linux-kernel@vger.kernel.org
Subject: Re: [Xen-users] 3.0.0-rc2: Xen: High amount of kernel "reserved" memory, about 33% in 256MB DOMU
Date: Mon, 13 Jun 2011 17:59:00 -0400 [thread overview]
Message-ID: <20110613215900.GB19117@dumpdata.com> (raw)
In-Reply-To: <20110613205003.GD20616@yumi.tdiedrich.de>
On Mon, Jun 13, 2011 at 10:50:03PM +0200, Tobias Diedrich wrote:
> Hi,
>
> another issue I'm seeing with 3.0-rc2 and Xen is that there is an
> unexpectedly high amount of kernel reserved memory.
>
> I suspect that Linux allocates page table entries and corresponding
> data structures for the whole 6GB areas of the provided 'physical
> RAM map' even though it has rather big unusable holes in it.
Can you run it with 'memblock=debug debug loglevel=8 initcall_debug'?
It should tell you where it tries (and for much space) the pagetables.
>
> [ 0.000000] BIOS-provided physical RAM map:
> [ 0.000000] Xen: 0000000000000000 - 000000000009f000 (usable)
> [ 0.000000] Xen: 000000000009f000 - 0000000000100000 (reserved)
> [ 0.000000] Xen: 0000000000100000 - 0000000010000000 (usable)
> [ 0.000000] Xen: 0000000010000000 - 000000007fef0000 (unusable)
> [ 0.000000] Xen: 000000007fef0000 - 000000007fef3000 (ACPI NVS)
> [ 0.000000] Xen: 000000007fef3000 - 000000007ff00000 (ACPI data)
> [ 0.000000] Xen: 00000000fec00000 - 0000000100000000 (reserved)
> [ 0.000000] Xen: 0000000100000000 - 000000016fef0000 (usable)
>
>
> On DOMUs I can 'fix' this by adding 'memmap=0x800000$0x100000000' to
> the kernel command line, which changes
>
> [ 0.000000] BIOS-provided physical RAM map:
> [ 0.000000] Xen: 0000000000000000 - 00000000000a0000 (usable)
> [ 0.000000] Xen: 00000000000a0000 - 0000000000100000 (reserved)
> [ 0.000000] Xen: 0000000000100000 - 0000000010000000 (usable)
> [ 0.000000] Xen: 0000000100000000 - 0000000100800000 (usable)
> [...]
> [ 0.000000] Memory: 176356k/4202496k available (6096k kernel code, 3932608k absent, 93532k reserved, 4785k data, 572k init)
>
> to
>
> [ 0.000000] BIOS-provided physical RAM map:
> [ 0.000000] Xen: 0000000000000000 - 00000000000a0000 (usable)
> [ 0.000000] Xen: 00000000000a0000 - 0000000000100000 (reserved)
> [ 0.000000] Xen: 0000000000100000 - 0000000010000000 (usable)
> [ 0.000000] Xen: 0000000100000000 - 0000000100800000 (usable)
> [...]
> [ 0.000000] user-defined physical RAM map:
> [ 0.000000] user: 0000000000000000 - 00000000000a0000 (usable)
> [ 0.000000] user: 00000000000a0000 - 0000000000100000 (reserved)
> [ 0.000000] user: 0000000000100000 - 0000000010000000 (usable)
> [...]
> [ 0.000000] user: 0000000100000000 - 0000000100800000 (reserved)
What happens if you have 'maxmem' value equal to 'memory' in your guest config?
> [ 0.000000] Memory: 244212k/262144k available (6096k kernel code, 448k absent, 17484k reserved, 4785k data, 572k init)
>
> With 66MB of usable memory out of 256MB recovered and a reasonable
> 93% of memory usable for userspace instead of just 67%.
>
>
> I also see this on my 256MB DOM0:
> Memory: 146536k/6028224k available (6122k kernel code, 3932612k absent, 1949076k reserved, 4761k data, 576k init)
> Only 143MB out of 256MB allocated for DOM0 is usable for userspace.
>
> Regards,
>
> --
> Tobias PGP: http://8ef7ddba.uguu.de
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
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next prev parent reply other threads:[~2011-06-13 22:52 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-13 20:50 [Xen-users] 3.0.0-rc2: Xen: High amount of kernel "reserved" memory, about 33% in 256MB DOMU Tobias Diedrich
2011-06-13 21:59 ` Konrad Rzeszutek Wilk [this message]
2011-06-14 0:10 ` Tobias Diedrich
2011-06-14 19:48 ` 3.0.0-rc2: Xen: High amount of kernel "reserved" memory, about 33% in 256MB DOMU [workaround included] Konrad Rzeszutek Wilk
2011-06-14 21:37 ` Tobias Diedrich
2011-06-14 21:14 ` [Xen-users] 3.0.0-rc2: Xen: High amount of kernel "reserved" memory, about 33% in 256MB DOMU Tobias Diedrich
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