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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.
As Samuel figured out later, this slowness may in fact be due to a Xen-specific
issue, see [[Xen_lseek]]. After the latter has been addressed, we can
re-evaluate this issue here.
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