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soc:2009:oremanj:journal:week4 [2009/06/19 02:59] rwcr |
soc:2009:oremanj:journal:week4 [2009/06/20 18:29] rwcr |
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| Tomorrow is rate control, figuring out a subset of 802.11 error codes to include human-readable definitions for, and cleaning all of this up to push it to mainline-review in time for Saturday's meeting. Hopefully I can manage it :-) | Tomorrow is rate control, figuring out a subset of 802.11 error codes to include human-readable definitions for, and cleaning all of this up to push it to mainline-review in time for Saturday's meeting. Hopefully I can manage it :-) | ||
| + | |||
| + | ==== Friday, 19 June ==== | ||
| + | * On branch **mainline-review**, something I did a while ago and forgot to port over: | ||
| + | * [[http://git.etherboot.org/?p=people/oremanj/gpxe.git;a=commit;h=6d63a4a5f928b46422e2eb79837a8aba103e5bb7| | ||
| + | [dhcp] Await link-up before starting DHCP]] | ||
| + | * On branch **wireless**, a bunch of small changes and one major new feature: | ||
| + | * [[http://git.etherboot.org/?p=people/oremanj/gpxe.git;a=commit;h=1a4ed46cb6a83a15828b250ebd0296775fd21ef4| | ||
| + | [802.11] Expose channel-changing functionality]] | ||
| + | * [[http://git.etherboot.org/?p=people/oremanj/gpxe.git;a=commit;h=48d2edc207edcee585b4a317e253e79af74fb290| | ||
| + | [iwmgmt] Make iwlist preserve existing associations, and be non-active]] | ||
| + | * [[http://git.etherboot.org/?p=people/oremanj/gpxe.git;a=commit;h=c110891fe4dd13f889792a2755e1637a5ecf7dfc| | ||
| + | [hci] Call iwlist without active argument, since it has been removed]] | ||
| + | * [[http://git.etherboot.org/?p=people/oremanj/gpxe.git;a=commit;h=fb129f1dcea8a81ec32ebd4c08be7c28716963b3| | ||
| + | [hci] Add wireless error lists]] | ||
| + | * [[http://git.etherboot.org/?p=people/oremanj/gpxe.git;a=commit;h=5ed61a78c6c8e412cf785587bbc7bd5eb46cbaa6| | ||
| + | [802.11] Add rate control support; fix two bugs; remove high rate bits]] | ||
| + | * [[http://git.etherboot.org/?p=people/oremanj/gpxe.git;a=commit;h=2f64f4fe523ce8d69c84077a0a29b3e1c6ef6b84| | ||
| + | [iwmgmt] Remove use of NET80211_RATE_VALUE]] | ||
| + | * [[http://git.etherboot.org/?p=people/oremanj/gpxe.git;a=commit;h=302ccbb4f84b97c655a009aa9708d946d1fbe95e| | ||
| + | [drivers rtl8180] Remove NET80211_RATE_VALUE; pass RX rate to netdev_rx()]] | ||
| + | |||
| + | I got rate control working today, and squashed a few other outstanding bugs that I found. With the rate-control algorithm in place, I was able to transfer a 13MB file over TFTP in 15 seconds on an 802.11g network with the access point about 12 feet away. For comparison, the same transfer over wired gigabit Ethernet took 4 seconds. I think the level this RC algorithm achieves is probably more than adequate for gPXE's performance requirements; there are various constants that can be tuned, but I'm not going to worry about that side of things right now. | ||
| + | |||
| + | I designed gPXE's rate-control algorithm mostly from scratch, based on my thoughts about how it would work well; a few aspects (such as the overriding rate decrease if we get 3 failed TXes) are based on Linux implementations. We keep data for every rate that could be used (<16 for all practical purposes), for the TX and RX paths separately, updating the TX information for our current TX rate when we receive TX completion status on a packet, and the RX information for a received packet's RX rate whenever we receive a data packet (management packets are generally sent at 1Mbps and so would skew the results). The data for each (rate, direction) combination is kept in a simple 32-bit integer, with two bits per packet (3 = OK, 2 = retried once, 1 = retried multiple times, 0 = didn't get through); when new packets are received old data is automatically shifted off the end, so that we always keep information for at most 16 packets for each (rate, direction) combination. The average of TX and RX qualities for a given rate, weighted by number of packets of data available for each and weighting TX packets more heavily than RX packets (they're more reliable), is munged into a "goodness" value for that rate between 0 and 99. Whenever the current rate's "goodness" falls below 85, we switch to the fastest rate with "goodness" over 85, or the rate with best "goodness" if none is over 85. | ||
| + | |||
| + | I got lucky with this one: the algorithm worked well as I designed it with only minor modifications, despite the fact that most of the numeric parameters would best be classified as educated guesses. :-) And it's quite small: | ||
| + | oremanj@xenon /home/oremanj/dev/gpxe % size src/bin/rc80211.o linux-2.6.30/net/mac80211/rc80211_minstrel.o | ||
| + | text data bss dec hex filename | ||
| + | 602 0 0 602 25a src/bin/rc80211.o | ||
| + | 3472 96 0 3568 df0 linux-2.6.30/net/mac80211/rc80211_minstrel.o | ||
| + | |||
| + | With the addition of rate control, and a few other bugfixes that came up while I was testing today, I think the wireless code is just about ready for mainline review. I'm going to go through over the weekend and make sure nothing is missing documentation, remove whitespace that's creeped onto line ends, and so forth; I plan to have everything I've worked on thus far over the summer in my mainline-review branch by Monday. | ||
| + | |||
| + | A quick size sanity check on the wireless code: | ||
| + | 220 24 0 244 f4 bin/iwmgmt_cmd.o | ||
| + | 602 0 0 602 25a bin/rc80211.o | ||
| + | 1479 56 0 1535 5ff bin/iwmgmt.o | ||
| + | 7282 100 24 7406 1cee bin/net80211.o | ||
| + | |||
| + | And for the rtl8180/rtl8185 driver: (only one of the RF handlers is required for any given card, in addition to rtl8180.o) | ||
| + | 3096 200 0 3296 ce0 bin/rtl8180.o | ||
| + | 1264 24 0 1288 508 bin/rtl8180_grf5101.o | ||
| + | 609 24 0 633 279 bin/rtl8180_max2820.o | ||
| + | 8174 24 0 8198 2006 bin/rtl8180_rtl8225.o | ||
| + | 985 24 0 1009 3f1 bin/rtl8180_sa2400.o | ||
| + | |||
| + | It's big by gPXE standards, but not enormous, and I think the size is reasonable given the complexity of the 802.11 protocol. And with the mucurses stuff (login and config) taken out but everything else default including iSCSI linked in, it meets the real test: | ||
| + | 68 -rw-r--r-- 1 oremanj oremanj 65024 2009-06-20 01:59 bin/rtl8180--rtl8180_rtl8225.rom | ||
| + | Under 64k---yippee! (With a completely default config it's 66,560 bytes.) Of course, the real challenge will be squeezing encryption support in there... but I've got the rest of the summer to figure that out ;-) | ||
| + | |||
| + | ==== Saturday, 20 June ==== | ||
| + | Everything has been pushed to mainline-review. :-) | ||
| + | * Branch **wireless**: deleted! | ||
| + | * On branch **mainline-review**: | ||
| + | * [[http://git.etherboot.org/?p=people/oremanj/gpxe.git;a=commit;h=4edf4718760dfb35c6a0c811fc2e019fb176e9fc| | ||
| + | [802.11] Add support for 802.11 devices with software MAC layer]] | ||
| + | * [[http://git.etherboot.org/?p=people/oremanj/gpxe.git;a=commit;h=b23fba30c9847b8fabf651d50cf6e4e323753548| | ||
| + | [rtl818x] Add driver for Realtek 8180/8185 wireless cards]] | ||
| + | * [[http://git.etherboot.org/?p=people/oremanj/gpxe.git;a=commit;h=dcd4ae5d0edbc9abd429bce50f0e58726cdfe00b| | ||
| + | [iwmgmt] Add user-level 802.11 management commands and common error tables]] | ||
| + | * [[http://git.etherboot.org/?p=people/oremanj/gpxe.git;a=commit;h=c35f15c32c3891711f0b0a99b8439aefd025b5ce| | ||
| + | Merge branch 'wireless' into mainline-review]] (merge style "ours", no modifications introduced) | ||
| + | |||
| + | Commits ready for mainline review, in reverse order: | ||
| + | oremanj@xenon /home/oremanj/dev/gpxe/src % git log --pretty=oneline --first-parent mainline-review | head -n 13 | ||
| + | dcd4ae5d0edbc9abd429bce50f0e58726cdfe00b [iwmgmt] Add user-level 802.11 management commands and common error tables | ||
| + | b23fba30c9847b8fabf651d50cf6e4e323753548 [rtl818x] Add driver for Realtek 8180/8185 wireless cards | ||
| + | 4edf4718760dfb35c6a0c811fc2e019fb176e9fc [802.11] Add support for 802.11 devices with software MAC layer | ||
| + | 6d63a4a5f928b46422e2eb79837a8aba103e5bb7 [dhcp] Await link-up before starting DHCP | ||
| + | 22c261e77bda0984f4cb052037008f487a4bcaa6 [hci] Expose ifcommon_exec() in a local header so wireless commands can use it | ||
| + | 30df822acbf6a207201f111d886effa0e4fc97d3 [ifmgmt] Move link-up status messages from autoboot() to iflinkwait() | ||
| + | 4602299f4b96f7692766553d5972066dfd567b4e [netdevice] Add netdev->link_rc field for errors encountered during link-up | ||
| + | 8041741323b40d9f5c482d3c6e1391bee7be759d [tcp] Ignore duplicate ACKs in TCP ESTABLISHED state | ||
| + | a9a0567225493046f70e6252e21ab5c6d8219e87 [image] Modify imgfree command to accept an argument | ||
| + | f77b486f42b2b12604ce94d65cbba33b55a589e5 [netdevice] Adjust maximum link-layer header length for 802.11 | ||
| + | d429b31ac28760004e753dc79178400d507975e2 [netdevice] Add netdev argument to link-layer push and pull handlers | ||
| + | 18e6470d06d8846d531d97d881be6f1278bd2f15 [nvs] Add init function for Atmel 93C66 EEPROM | ||
| + | |||
| + | Next up: encryption! | ||
