Systimer stuff

Matt Dillon’s been working on this patch, described as so:

“These are dyamic[sic] interrupt-driven timers. They replace the old fixed periodic ‘hardclock’ interrupt that exists now and allow per-cpu multiple periodic or one-shot timer interrupts to be registered with the system. Systimers operate outside the MP lock, so any code developed to use it has to be MP safe. Systimers are intended to be able to make use of per-cpu timers (e.g. LAPIC), when available, and will eventually be augmented to use them.”

It also has the added bonus of making nanosleep() very accurate.

gcc 3 going on

Joerg Sonnenberger has added gcc 3.3 to the base system. You can set ‘CCVER=gcc3’ to use it, even to do a buildworld/buildkernel, though that is “not recommended”. Andreas Hauser already reported a successful build and boot doing it, though.

xl expanded

Matt Dillon has made some changes to the xl driver that apparently solves a mysterious bug; I’m quoting from his changelog message below:

“Turn off hardware assisted transmit checksums by default. In buildworld loop tests this has been conclusively shown to corrupt transmit packets about one out of every million packets. The receive will not know the the packet is bad because hardware assist also apples the correct checksum to the corrupted packet. The result are random failures or corruption of network data in certain situations. On DragonFly, for some reason, doing a ‘resident /usr/bin/*’ seems to bring the problem out every few buildworlds with (primarily) mkdep’s cpp complaining about odd errors trying to open non-existant header files (during a header file search), such as EPROTONOSUPPORT. A tcpdump on both NFS client and server showed the client transmitting an access RPC and the server seeing a corrupted access RPC on its end, and then responding with EPROTONOSUPPORT. Other uncaught errors are also almost certainly occuring. mkdep is more likely to catch them because it actually checks the errno of a failed open() and does a huge number of open()’s (and as an NFS client this generates a huge amount of packet traffic).”

Debugging options

Matt Dillon noted that:

makeoptions DEBUG=-g
options DDB
options INVARIANTS
options INVARIANT_SUPPORT

are the only options you need when building with debugging options on.

Faster file descriptor allocation

Skip Ford ported Tim Robbins’ FreeBSD port of Niels Provos’ NetBSD file descriptor allocation code. Normally I don’t post about code until it gets committed, but he posted some numbers on how well it improves things, as benchmarked by Niels Provos’ test program that opens/closes files repeatedly. The numbers seem to indicate a 50% speedup:

File DescriptorsUnpatchedPatched
10.7656500.781279
20011.1484840.789092
40011.5469350.765657
60012.0625820.781276
80012.5157250.796906
100013.0860610.796904
120013.6329550.765654
140014.0860980.757841
160014.5158050.820343
180014.9767590.812530
200015.4299160.796905
220015.8986520.773467
240016.3361880.773455
260016.7502680.804718
280017.1799720.789091
300017.6331100.781281
320018.0706320.789091
340018.5237710.796906
360018.9534790.789092
380019.3753700.765656
4000110.1175870.789090
4200110.7582380.789091
4400111.3676360.804718
4600111.8207810.812531
4800112.4536180.812530

Sound support superior

Thanks to Emiel Kollof (sorry I screwed up attribution!), AC97 support has been synced up with FreeBSD, plus support for the following devices has been added by Jeroen Ruigrok:

Diamond Technology Monster (DT0398)
Intersil (Harris) HMP9701
Integrated Technology Express (ITE) ITE2226E and ITE2646E
Texas Instruments TLC320AD90
Winbond W83971D
Asahi Kasei AK4544A and AK4545
Realtek ALC850
Wolfson WM9711L, WM9712L, and WM9709
Texas Instruments’ TLV320AIC27
Conexant SmartDAA HSD11246

Resident Good

Matt Dillon is bringing in resident executable support. This speeds loading of dynamically linked programs by saving a copy of their vmspace with vmspace_fork() in the kernel, and using that when executed instead of going through the regular, slower startup. This will replace prebinding.

Matt Dillon posted these preliminary numbers running a test program with Perl:

dynamic:2.860u 2.668s 0:05.61 98.3% 87+231k 0+0io 0pf+0w
prebinding:1.821u 2.095s 0:03.90 100.2% 34+202k 0+0io 1pf+0w
resident:1.239u 1.846s 0:03.08 99.6% 137+280k 0+0io 0pf+0w
statically linked:0.418u 0.867s 0:01.28 99.2% 808+616k 0+0io 0pf+0w

It is planned to make dynamic loading as fast as static. For those of you not familiar with the output of time, the first column is total time taken, the second is time taken to run the tested program, and the third is time consumed by system overhead. Yes, there are more columns than that. No, I don’t know what they mean.

A journaling journey

Discussion continues on journaling, soft updates, and background fsck. Jeroen van Gelderen linked to “Design Evolution of the EROS Single-Level Store” while talking about journaling meta-data, and Matt Dillon mentioned that he and David Rhodus are putting together a kernel API for journaling, so that some ambitious person can build it. Matt Dillon also pointed out he favors journaling because softupdates is a complex beast, and modern IDE drives are somewhat undependable when it comes to the way they lay down data. As an added bonus, Diego Calleja GarcĂ­a linked to a description of reiser4 which talks about journaling, along with some freaky illustrations.

M_NOWAIT NOGOOD

Matt Dillon noticed in a thread on the freebsd-hackers mailing list (see here for original post, and look for articles following that have [CHECKER] in the subject) that the M_NOWAIT command is being used incorrectly in a number of places, both in DragonFly and in FreeBSD.

I’m just pasting the rest of his post, as it’s not something that boils down easily:
Continue reading “M_NOWAIT NOGOOD”

Plans and other plans

As part of a discussion about internationalization, Matt Dillon mentioned he plans to finish IPC this weekend as it would be a useful implementation method. He also mentioned offhand that the first release of DragonFly could be in June/July.

645dx tricks

Bernhard Valenti found he had to put “set hw.ata.ata_dma=0” in the boot loader to get his 645DX-based motherboard ATA working. Jeroen Ketema also found that write caching had to be off: “set hw.ata.wc=0