[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-users] 3.0.0-rc2: Xen: High amount of kernel "reserved" memory, about 33% in 256MB DOMU
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 > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ _______________________________________________ Xen-users mailing list Xen-users@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-users
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