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[[!meta copyright="Copyright © 2010, 2011 Free Software Foundation, Inc."]]
[[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable
id="license" text="Permission is granted to copy, distribute and/or modify this
document under the terms of the GNU Free Documentation License, Version 1.2 or
any later version published by the Free Software Foundation; with no Invariant
Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license
is included in the section entitled [[GNU Free Documentation
License|/fdl]]."]]"""]]
[[!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]]
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