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authorSamuel Thibault <samuel.thibault@ens-lyon.org>2015-02-18 00:58:35 +0100
committerSamuel Thibault <samuel.thibault@ens-lyon.org>2015-02-18 00:58:35 +0100
commit49a086299e047b18280457b654790ef4a2e5abfa (patch)
treec2b29e0734d560ce4f58c6945390650b5cac8a1b /open_issues/performance/io_system/binutils_ld_64ksec.mdwn
parente2b3602ea241cd0f6bc3db88bf055bee459028b6 (diff)
Revert "rename open_issues.mdwn to service_solahart_jakarta_selatan__082122541663.mdwn"
This reverts commit 95878586ec7611791f4001a4ee17abf943fae3c1.
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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.
+
+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.