summaryrefslogtreecommitdiff
path: root/community/gsoc/project_ideas/disk_io_performance.mdwn
blob: bb047308dfd419f9718882889aea66402aa2abec (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
[[!meta copyright="Copyright © 2008, 2009 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="Disk I/O Performance Tuning"]]

The most obvious reason for the Hurd feeling slow compared to mainstream
systems like GNU/Linux, is very slow harddisk access.

The reason for this slowness is lack and/or bad implementation of common
optimisation techniques, like scheduling reads and writes to minimalize 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
optimisations at a higher logical level.

The goal of this project is to analyze the current situation, and implement/fix
various optimisations, to achieve significantly better disk performance. It
requires understanding the data flow through the various layers involved in
disk acces on the Hurd ([[filesystem|hurd/virtual_file_system]],
[[pager|hurd/libpager]], driver), and general experience with
optimising 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.

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.