From b7ba1377b7c712e42275f2c8055974dc2a48a0e4 Mon Sep 17 00:00:00 2001 From: Thomas Schwinge Date: Sat, 6 Nov 2010 10:27:05 +0100 Subject: open_issues/performance: New. --- open_issues/io_system_binutils_ld_64ksec.mdwn | 33 ---------------- .../io_system_binutils_ld_64ksec/test.tar.xz | Bin 378092 -> 0 bytes open_issues/performance.mdwn | 11 ++++++ open_issues/performance/io_system.mdwn | 42 +++++++++++++++++++++ .../performance/io_system/binutils_ld_64ksec.mdwn | 33 ++++++++++++++++ .../io_system/binutils_ld_64ksec/test.tar.xz | Bin 0 -> 378092 bytes 6 files changed, 86 insertions(+), 33 deletions(-) delete mode 100644 open_issues/io_system_binutils_ld_64ksec.mdwn delete mode 100644 open_issues/io_system_binutils_ld_64ksec/test.tar.xz create mode 100644 open_issues/performance.mdwn create mode 100644 open_issues/performance/io_system.mdwn create mode 100644 open_issues/performance/io_system/binutils_ld_64ksec.mdwn create mode 100644 open_issues/performance/io_system/binutils_ld_64ksec/test.tar.xz (limited to 'open_issues') diff --git a/open_issues/io_system_binutils_ld_64ksec.mdwn b/open_issues/io_system_binutils_ld_64ksec.mdwn deleted file mode 100644 index 0484137a..00000000 --- a/open_issues/io_system_binutils_ld_64ksec.mdwn +++ /dev/null @@ -1,33 +0,0 @@ -[[!meta copyright="Copyright © 2010 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. - -It is taken from the [[binutils_testsuite]], `ld/ld-elf/sec64k.exp`, where this -test may occasionally [[trigger a timeout|binutils_testsuite#64ksec]]. It is -extracted from cdf7c161ebd4a934c9e705d33f5247fd52975612 sources, 2010-10-24. - - $ wget -O - http://www.gnu.org/software/hurd/open_issues/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. diff --git a/open_issues/io_system_binutils_ld_64ksec/test.tar.xz b/open_issues/io_system_binutils_ld_64ksec/test.tar.xz deleted file mode 100644 index 6d7c606c..00000000 Binary files a/open_issues/io_system_binutils_ld_64ksec/test.tar.xz and /dev/null differ diff --git a/open_issues/performance.mdwn b/open_issues/performance.mdwn new file mode 100644 index 00000000..3ffffa4d --- /dev/null +++ b/open_issues/performance.mdwn @@ -0,0 +1,11 @@ +[[!meta copyright="Copyright © 2010 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]]."]]"""]] + + * [[I/O System|io_system]] diff --git a/open_issues/performance/io_system.mdwn b/open_issues/performance/io_system.mdwn new file mode 100644 index 00000000..bf59b5df --- /dev/null +++ b/open_issues/performance/io_system.mdwn @@ -0,0 +1,42 @@ +[[!meta copyright="Copyright © 2008, 2009, 2010 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]]."]]"""]] + +[[!meta title="I/O System"]] + +[[!tag open_issue_hurd]] + +The most obvious reason for the Hurd feeling slow compared to mainstream +systems like GNU/Linux, is a low I/O system performance, in particular very +slow hard disk access. + +The reason for this slowness is lack and/or bad implementation of common +optimization techniques, like scheduling reads and writes to minimize head +movement; effective block caching; effective reads/writes to partial blocks; +reading/writing multiple blocks at once; and read-ahead. The +[[ext2_filesystem_server|hurd/translator/ext2fs]] might also need some +optimizations at a higher logical level. + +The goal of this project is to analyze the current situation, and implement/fix +various optimizations, to achieve significantly better disk performance. It +requires understanding the data flow through the various layers involved in +disk access on the Hurd ([[filesystem|hurd/virtual_file_system]], +[[pager|hurd/libpager]], driver), and general experience with +optimizing complex systems. That said, the killing feature we are definitely +missing is the read-ahead, and even a very simple implementation would bring +very big performance speedups. + +Here's a real use-case: [[binutils_ld_64ksec]]. + +Possible mentors: Samuel Thibault (youpi) + +Exercise: Look through all the code involved in disk I/O, and try something +easy to improve. It's quite likely though that you will find nothing obvious -- +in this case, please contact us about a different exercise task. diff --git a/open_issues/performance/io_system/binutils_ld_64ksec.mdwn b/open_issues/performance/io_system/binutils_ld_64ksec.mdwn new file mode 100644 index 00000000..60dca510 --- /dev/null +++ b/open_issues/performance/io_system/binutils_ld_64ksec.mdwn @@ -0,0 +1,33 @@ +[[!meta copyright="Copyright © 2010 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. + +It is taken from the [[binutils_testsuite]], `ld/ld-elf/sec64k.exp`, where this +test may occasionally [[trigger a timeout|binutils_testsuite#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. diff --git a/open_issues/performance/io_system/binutils_ld_64ksec/test.tar.xz b/open_issues/performance/io_system/binutils_ld_64ksec/test.tar.xz new file mode 100644 index 00000000..6d7c606c Binary files /dev/null and b/open_issues/performance/io_system/binutils_ld_64ksec/test.tar.xz differ -- cgit v1.2.3