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gcc 4.7 in, gcc 4.1 out

John Marino has accomplished the difficult task of putting gcc 4.7 into DragonFly.  Version 4.4 is still the default, and the older 4.1 version has been disabled.  If you want to try this newer version, setting WORLD_CCVER=gcc47 will build kernel and world that way too.  If you’re curious about what’s different in this version of gcc, there’s a 4.7 changelog.

Are we the only BSD with this new a version in base?  I think so.

P.S.: You’ll want to do a full buildworld if you’re running DragonFly 3.1

P.P.S.: you may need to put ‘NO_GCC47=true’ in make.conf, going from IRC comments.

P.P.P.S.: Nope, now it’s fine.

 

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A flurry of fixes and scheduler improvements

The combination of Mihai Carabas’s successful Summer of Code work on the scheduler and the recent Postgres benchmarking got Matthew Dillon to start thinking about making UNIX domain sockets work better, a shortcut around the buffer cache, scheduler improvements and then a new default scheduler, along with a change in idle CPU behavior.  The best place to understand all the changes is in his long post to users@.

We should have benchmarks soon to show the performance improvements from all this.

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Experimental pmap optimizations

Matthew Dillon has created an experiment: shared page table mappings.  It’s controlled by a sysctl, since it’s still experimental.  The real-world effect is reducing the number of memory faults as a process uses up memory, and decreasing the overall memory usage.  The obvious benchmark is Postgres speed; this makes the initial expansion of memory usage much less of an drag on speed due to a high memory fault rate.

If all this mention of faulting sounds like a problem, remember memory faults on BSD are normal; that’s how programs indicate they need more memory space by causing a fault.  This is in contrast to Linux, where memory is allocated a different way.  Or at least, that’s my understanding.  (If you know better, please comment.)

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Hammer 2 status report

Matthew Dillon recent posted a status report for Hammer 2.  Of interest is the spanning tree protocol being built to handle messages between Hammer volumes.  As he says in the message:

For example, we want to be able to have millions of diskless or cache-only clients be able to connect into a cluster and have it actually work…

(No, it doesn’t do this, yet.)

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A change for bc(1), no change for man

Pierre Abbat noticed that bc(1)‘s usage of GNU readline something that wasn’t GNU readline made it harder to use; Sascha Wildner changed it to use libedit.  Pierre’s other complaint, that BSD man page output stays on-screen when completed, is a positive feature.  Linux systems that clear man page output enrage me, because I expect to be able to take advantage of my scroll buffer.

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gcc47 means gcc-aux for you

John Marino has added a ‘gcc47’ compiler ccvar, so you can build world and kernel with it.  ‘It’ is actually gcc-aux, since it seems to work better than the basic (“vanilla”?)  gcc47.  You also get Ada support, though that wasn’t the driving reason to pick it.  This is brand new so don’t try it unless you’re ready to discover issues.

Is there any other BSD able to use gcc 4.7 for world/kernel?  Even 4.6?  Most of the attention has been on clang.

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Other ways to use lint

Sascha Wildner has made it easier to use alternative syntax checking systems as a “lint” make target in DragonFly.  His usage of coccinelle, as one of these alternatives, has already found many bugs – just today, for instance.

Is “alternative syntax checking systems” the right phrase for this?  I don’t know.  “Correctness checker”?  My phrases all sound like something you’d read on a government form.