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[ikiwiki.git] / docs / developer / alexh_todo / index.mdwn
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b475db1d 1## Note: this is my personal todo and ideas list (alexh@)
49a92aaf 2
fcd780c0 3* add a non-persistent unionfs VFS
4 - while this does not fully replace unionfs, it would deal with a few of the situations where unionfs is useful
5 - additionally the complexity is much lower, since everything can be kept in memory
6
7* bring the samba3 hammer shadow copy foo to maturity
8
d2e33566 9* add a communication channel mechanism to dm
10 - essentially a way to send messages and receive responses to dm target instances
11
d3f270a8 12* add another optimized bcopy/memcpy/memset/bzero version, using the AVX instructions
13
6e280d9e 14* Add TrueCrypt support
15 - Simply add a userland tool that sets dm_target_crypt up with the right parameters, extracted from the TrueCrypt header
5d279a75 16 - https://github.com/bwalex/tc-play <- done!
5eba61c7 17 - need passphrase read timeout support
ae466a83 18 - need unmap support
5eba61c7 19 - cryptdisks: needs generic crypto options; multiple keyfile support
6e280d9e 20
e09e6796 21* Update cryptsetup
22
85fee687 23* Keep opencrypto up-to-date
744c3358 24 - http://www.openbsd.org/cgi-bin/cvsweb/src/sys/crypto/
25
e09e6796 26* Port hwpmc & dig into (boot-up) performance
27
1bf667d1 28* linuxulator
6c260381 29 - port to x86_64
30 - separate out common arch parts (linprocfs, for example)
53af51d2 31
e09e6796 32* Fix the crash analysis script (or rather the programs it calls [some segfault])
0d62372b 33
f3169700 34* Take a look at updating lvm/dm/libdevicemapper
53af51d2 35
f3169700 36* Take a look at importing libdm from NetBSD
37 - would allow tc-play and similarly newly developed foo to avoid GPL license issues
1bf667d1 38
6c260381 39* rip out the disk partitioning from the disk subsystem and implement it in a more general fashion
40 - crazy idea: as dm targets with an auto-configuration option!
b7038718 41 - would require to be able to create dm targets with an arbitrary name and not in /dev/mapper
6c260381 42
1bf667d1 43* ATA (automatic) spindown (see FreeBSD current)
0d62372b 44
45* Update callout
46 http://svn.freebsd.org/viewvc/base?view=revision&revision=127969
47
48* inv ctxsw rusage
49 - see irc logs
50 - some incorrect accounting going on, don't remember details :)
51
52* unionfs update
53 - make it work without whiteout
54
55
56
b475db1d 57###Boring:
1bf667d1 58
772830b5 59* Fix ipsec, get rid of old ipsec
60
f4ce1567 61* sync up vr
62 - Added VT6105M specific register definitions. VT6105M has the following hardware capabilities.
63 - Tx/Rx IP/TCP/UDP checksum offload.
64 - VLAN hardware tag insertion/extraction. Due to lack of information
65 for getting extracted VLAN tag in Rx path, VLAN hardware support
66 was not implemented yet.
67 - CAM(Content Addressable Memory) based 32 entry perfect multicast/
68 VLAN filtering.
69 - 8 priority queues.
70 o Implemented CAM based 32 entry perfect multicast filtering for
71 VT6105M. If number of multicast entry is greater than 32, vr(4)
72 uses traditional hash based filtering.
1bf667d1 73
74* RedZone, a buffer corruption protection for the kernel malloc(9) facility has been implemented.
75 - This detects both buffer underflows and overflows at runtime on free(9) and realloc(9),
76 and prints backtraces from where memory was allocated and from where it was freed.
77 - see irc log below.
78
79* port uart driver (?)
80
0d62372b 81* port wscons (?) or update syscons
82 - probably way too much effort (wscons)
83
84
85* port usb4bsd
86 - wrapper is included for userland; should be easy to port
87 - http://svn.freebsd.org/viewvc/base?view=revision&revision=184610
88 - http://turbocat.net/~hselasky/usb4bsd/
89 - http://gitweb.dragonflybsd.org/~polachok/dragonfly.git/shortlog/refs/heads/usb2
90
1bf667d1 91* suspend/resume for SMP x86
92 - http://lists.freebsd.org/pipermail/freebsd-acpi/2008-May/004879.html
93
1bf667d1 94* AMD64 suspend/resume
95 - http://svn.freebsd.org/viewvc/base?view=revision&revision=189903
6c260381 96
97
6c260381 98* text dumps
99
1bf667d1 100
1bf667d1 101
102[alexh@leaf:~/home] $ roundup-server -p 8080 bt=bugtracker
103
53af51d2 104<pre>
1bf667d1 105-05:48- : dillon@: no, double frees to the object cache are nasty. It can't detect them. the object
106 winds up in the magazine array twice
107-05:48- : dillon@: (and possibly different magazines, too)
108-05:49- : alexh@: can't I just write some magic to a free object on the first objcache_put and check
109 if it's there on objcache_put?
110-05:49- : alexh@: and clear it on objcache_get, anyways
111-05:50- : dillon@: no, because the object is still may have live-initialized fields
112-05:50- : dillon@: because it hasn't been dtor'ed yet (one of the features of the objcache, to avoid
113 having to reinitialize objects every time)
114-05:50- : dillon@: the mbuf code uses that feature I think, probably other bits too
115-05:51- : dillon@: theoretically we could allocate slightly larger objects and store a magic number at
116 offset [-1] or something like that, but it gets a little iffy doing that
117-05:52- : dillon@: the objcache with the objcache malloc default could probably do something like that
118 I guess.
119-05:52- : dillon@: I don't consider memory tracking to be a huge issue w/ dragonfly, though I like the
120 idea of being able to do it. It is a much bigger problem in FreeBSD due to the
121 large number of committers
122
123
124-05:55- : dillon@: For the slab allocator you may be able to do something using the Zone header.
125-05:55- : dillon@: the slab allocator in fact I think already has optional code to allocate a tracking
126 bitmap to detect double-frees
127-05:56- : dillon@: sorry, I just remembered the bit about the power-of-2 allocations
128-05:56- : dillon@: for example, power-of-2-sized allocations are guaranteed not only to be aligned on
129 that particular size boundary, but also to not cross a PAGE_BOUNDARY (unless the
130 size is > PAGE_SIZE)
131-05:57- : dillon@: various subsystems such as AHCI depend on that behavior to allocate system
132 structures for which the chipsets only allow one DMA descriptor.
133-05:59- : alexh@: http://svn.freebsd.org/viewvc/base/head/sys/vm/redzone.c?view=markup&pathrev=155086
134 < this is redzone. it basically calls redzone_addr_ntor() to increase the size in
135 malloc(), and then redzone_setup() just before returning the chunk
136-06:02- : dillon@: jeeze. that looks horrible.
137-06:03- : alexh@: I don't quite get that nsize + redzone_roundup(nsize)
138-06:03- : dillon@: I don't get it either. It would completely break power-of-2-sized alignments in the
139 original request
140-06:04- : dillon@: hmmm. well, no it won't break them, but the results are oging to be weird
141-06:04- : dillon@: ick.
142
143-06:15- : dillon@: if the original request is a power of 2 the redzone adjusted request must be a power
144 of 2
145-06:15- : dillon@: basically
146-06:16- : dillon@: so original request 64, redzone request must be 128, 256, 512, 1024, etc.
147-06:16- : alexh@: yah, k
148-06:16- : dillon@: original request 32, current redzone code would be 32+128 which is WRONG.
149-06:16- : alexh@: how big is PAGE_SIZE ?
150-06:16- : dillon@: 4096 on i386 and amd64
151-06:17- : alexh@: and one single malloc can't be bigger than that?
152-06:17- : dillon@: I'm fairly sure our kmalloc does not guarantee alignment past PAGE_SIZE (that is,
153 the alignment will be only PAGE_SIZE eve if you allocate PAGE_SIZE*2)
154-06:17- : dillon@: a single kmalloc can be larger then PAGE_SIZe
155-06:18- : dillon@: it will use the zone up to around 1/2 the zone size (~64KB I think), after which it
156 allocates pages directly with the kernel kvm allocator
157-06:18- : dillon@: if you look at the kmalloc code you will see the check for oversized allocations
158-06:18- : alexh@: yah, saw that
159-06:18- : alexh@: "handle large allocations directly"
160-06:19- : alexh@: not sure how to do this, really, as the size is obviously also changed in
161 kmem_slab_alloc
162-06:20- : alexh@: but kmem_slab_alloc isn't called always, is it?
163-06:20- : alexh@: only if the req doesn't fit into an existant zone
164-06:20- : dillon@: right
165-06:20- : dillon@: you don't want to redzone the zone allocation itself
53af51d2 166
167</pre>