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[[!tag open_issue_xen]]

IRC, freenode, #hurd, 2011-11-02:

    <youpi> btw, we have a performance issue with xen
    <youpi> an lseek() call costs a huge lot
    <youpi> like 1ms
    <youpi> while the same costs just a few dozens µs with kvm
    <youpi> there's of course the cost of switching between ring3, ring0,
      ring1, ring0, ring3, but still
    <gianluca> oh, nice.
    <youpi> lseek is supposed to perform only a back&forth
    <youpi> and I don't observe disk activity, so it's not waiting for the disk
      to complete whatever atime change & such :)
    <youpi> it was mentioned that perhaps xen in hvm mode with pv drivers would
      be faster
    <youpi> thanks to the ring3/"1" switching  being done by the processor
    <youpi> (and assuming npt)
    <gianluca> hm
    <gianluca> i'll look into that, sounds fun.
    <gianluca> :)
    <tschwinge> Here is a testcase:
      http://www.gnu.org/software/hurd/open_issues/performance/io_system/binutils_ld_64ksec.html

[[performance/io_system/binutils_ld_64ksec]].