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[[!tag open_issue_hurd]]

This one may be considered as a testcase for [[I/O system
optimization|community/gsoc/project_ideas/disk_io_performance]].

It is taken from the [[binutils testsuite|binutils]],
`ld/ld-elf/sec64k.exp`, where this
test may occasionally [[trigger a timeout|binutils#64ksec]].  It is
extracted from cdf7c161ebd4a934c9e705d33f5247fd52975612 sources, 2010-10-24.

    $ wget -O - http://www.gnu.org/software/hurd/open_issues/performance/io_system/binutils_ld_64ksec/test.tar.xz | xz -d | tar -x
    $ cd test/
    $ \time ./ld-new.stripped -o dump dump?.o dump??.o
    0.00user 0.00system 2:46.11elapsed 0%CPU (0avgtext+0avgdata 0maxresident)k
    0inputs+0outputs (0major+0minor)pagefaults 0swaps

On the idle grubber, this one repeatedly takes a few minutes wall time to
complete successfully, contrary to a few seconds on a GNU/Linux system.

While processing the object files, there is heavy interaction with the relevant
[[hurd/translator/ext2fs]] process.  Running [[hurd/debugging/rpctrace]] on
the testee shows that (primarily) an ever-repeating series of `io_seek` and
`io_read` is being processed.  Running the testee on GNU/Linux with strace
shows the equivalent thing (`_llseek`, `read`) -- but Linux' I/O system isn't
as slow as the Hurd's.

---

IRC, freenode, #hurd, 2011-09-01:

    <youpi> hum, f951 does myriads of   71->io_seek_request (32768 0) = 0 32768
    <youpi> no wonder it's slow
    <youpi> unfortunately that's also what it does on linux, the system call is
      just less costly
    <youpi> apparently gfortran calls io_seek for, like, every token of the
      sourced file
    <youpi> (fgetpos actually, but that's the same)
    <youpi> and it is indeed about 10 times slower under Xen for some reason

[[!tag open_issue_xen]]