[Xen-devel] why do I get bad disk write performance in the kernel 3.1?

[Roberto Scudeller <beto.rvs@xxxxxxxxx>]

Hi all,

I'm testing the new kernel 3.1 from kernel.org, and xen 4.1.2-rc1-pre. 
I execute a CrystalMark IO Benchmark, in windows 2003 VM with gplpv drivers, and receive an amazing result for reading, but the write numbers are very disappointing.

I run the VM in local disk, and receive these numbers:
Seq read: 244 MB/s
512K read: 239 MB/s
4K read: 27 MB/s
4K QD 32: 90 MB/s

Seq write: 20 MB/s
512K: 20 MB/s
4K: 8 MB/s
4K QD 32: 12MB/s

In older kernel, 2.6.32.x:
Seq read: 189 MB/s
512K read: 169 MB/s
4K read: 11 MB/s
4K QD 32: 34 MB/s

Seq write: 177 MB/s
512K: 166 MB/s
4K: 12 MB/s
4K QD 32: 36 MB/s

Could anyone help me. Why is the new kernel faster in reading, but too slow writing ?

-- 
Roberto Scudeller


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