summaryrefslogtreecommitdiff
path: root/microkernel/viengoos/projects/new_hash_function.mdwn
blob: d0374720140cc0844af08676962bc1a77d8a18e2 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
[[!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]]."]]"""]]

[[!tag open_issue_viengoos]]

The current hash function in libhurd-ihash results in a lot of
collisions when the hash table is 80% full.  To overcome this, we keep
hash tables at most 30% full.  This represents a fair amount of
overhead.  Find a better algorithm.  There can either be one that is
appropriate in the general case or one that works well in a relevant,
specific case, e.g., viengoos/object.c uses a hash to find the object
corresponding to a frame, which is keyed on its physical address.

Note that this applies to the Hurd's [[hurd/libihash]], too.