By the time you read this I'll be back home again after the#
Sun, 03 Aug 2003 22:00:33 +0000
By the time you read this I'll be back home again after the
UKUUG's Linux 2003 summer conference, at which I was speaking on
"Native threads for SBCL". The paper is at http://www.linux.org.uk/~dan/linux2003/; I'm told it's also on
the conference CD and may also end up on the UKUUG web site
And the slides. Well ...
On Wednesday I roughed out how many slides I should do (one for
every two minutes) and the titles. By mid-afternoon on Friday I'd
more or less decided on the body content too. This was all in a text
file, so should be easy to turn it into a presentation, were it not
for some fairly strange requirements I have for a usable presentation
- Able to run happily on my laptop (only 128Mb RAM, much of
which is already used by Emacs and Mozilla Firebird). This makes
OpenOffice and the like a non-starter.
- Easy to use without a mouse, because I only have the touchpoint
mouse substitute. Which works perfectly for most of my mouse use
(window focus) but starts to get tedious for any work demanding more
accuracy than clicking on web links.
- You're thinking that magicpoint fits the bill, right. Well, it
would do, but, please, God, don't make me have to use magicpoint
again. It has that strange m4-like property of making the easy things
easy and the slightly more difficult things (like, say, switching to
typewriter font and back on the same slide without either
breaking my carefully indented code or putting the following bullet
point somewhere utterly weird) nightmarishly awkward. And the
documentation is kind of iffy.
So, after the Scottish Buffet (a Scottish Buffet, it appears, is
what we in England call a "sit-down meal", although no less tasty for
all that) on Friday evening I headed back to my room, paged through
the slide text for a few minutes, and when I next looked up it was
early on Saturday morning and I'd written the bare bones of a
presentation graphics program using CL - my first CLX program, too.
(Yes, that's right, I maintain(sic) a CLX port for SBCL despite never
yet having written anything that uses it)
Matters arising, in no particular order
- There's a bug in CLX's with-gcontext macro. Or at least, it
certainly doesn't do as I ask
- I need to add a word-wrap algorithm. Eventually (I also had a
conference to attend while developing it, so there was limited
concentrated hacking time available) I had to stop fiddling with it
and just add line breaks to the source file. Newlines are kind of
dodgy, too, and I also need to find a less blocky title font.
- I used it for the presentation. It worked, and didn't crash.
The screensaver leapt into action a couple of times - I should add an
onscreen "you have lingered on this slide too long" indication,
because having the whole thing turn black is a bit unsubtle
- CLX programming is surprisingly painless, at least given the
manual. The next version of telent clx will include such a thing,
based on the manual at Gilbert Baumann's site
- That URL again: http://www.linux.org.uk/~dan/linux2003/. If you want to play
with the presentation thing, viewer.lisp is the appropriate
file. Needs SBCL CLX for open-default-display, which you could
easily replace with open-display cruft if you're running some other
- It may be subjected to more hacking in future: all depends on how
often i find I need to give presentations. The observant will note
from the defpackage form that I've called it Acclaim.
More about the conference itself later.
Having had the same email address since sometime in 1996, and being a#
Wed, 06 Aug 2003 20:09:37 +0000
Having had the same email address since sometime in 1996, and being a
fairly frequent poster on usenet, I get a lot of spam. Enough in
fact, that I can delete it by hand faster and more accurately than
spamassassin can, even just looking at the subject/sender name. (Yes,
that's right, I got annoyed with my spam filters and turned them off again)
Anyway, I thought this one was funny:
From: Leslie Oneal<email@example.com>
I am contacting you about cross linking. I am interested in telent.net because
+it looks like it's relevant to a site that I am the link manager for. The site
+is about search engine optimization research and technology for top search
I keep the web address confidential and will send it to you only if you give me
+permission to do so. Just let me know if it's OK, and I'll send you the web
+address for your review. If you approve of the site, then we'll exchange links.
Now, I'm no more of an expert in "search engine optimization" than
the next man, tending to believe that you can get some pretty good
rankings on search engines simply by providing useful or interesting
content that people want to link to, but even I know that
omitting to tell people the address of your site is not the best way
to increase traffic to it.
So I guess the question is: exactly how gullible does one have to
be to fall for this rubbish?
Thu, 07 Aug 2003 15:27:46 +0000
http://www.function-pointer.org/. Can you say
"Greenspun's Tenth Rule of Programming"?
What I should be doing: hacking on CLiki to allow two cliki instances#
Fri, 08 Aug 2003 14:19:51 +0000
What I should be doing: hacking on CLiki to allow two cliki instances
to share the same pages (and the same methods for
search-term-relevance and the rest), so that we can have multiple
`skins' for the same data.
Yes, I'm sure that's theoretically possible with CSS. The prospect
of making any CSS solution work on IE5 and Netscape 4 is neither warm
nor fuzzy, though.
What I'm doing instead: fixing the SBCL condition-variable bugs
that Gilbert found. I attempt to justify this to myself by claiming
that my productivity will take a leap when Portable
Hemlock gets good enough to dump ILISP.
One of my ambitions w.r.t Lisp packaging is to make the ancient#
Sun, 10 Aug 2003 20:48:20 +0000
One of my ambitions w.r.t Lisp packaging is to make the ancient
CMU Common Lisp on Linux document
OK, so I could achieve that (and in fact, have) just by leaving it
three years without an update, so perhaps I should restate that goal
more clearly: I want to make this document (and others like it)
Anyway, another step further down that road today, with the release
of asdf-install into
an unsuspecting SBCL CVS tree. Now we can download and install CCLAN
modules from the command line (or from inside a running Lisp)
This week, Jakob Nielsen's #
Mon, 11 Aug 2003 17:30:00 +0000
This week, Jakob Nielsen's
Excessive word count and worthless details are making it harder for
people to extract useful information. The more you say, the more
people tune out your message.
then goes on to prove the point with another 500 words.
Once again I find myself in that place where something that sounds#
Fri, 15 Aug 2003 16:52:26 +0000
Once again I find myself in that place where something that sounds
like a half-hour hack turns out to take all day and still doesn't
work. This time it's implementing interrupt-thread
(traditionally called process-interrupt), and, being lazy, I'm
going to point you at the sbcl-devel article I wrote earlier this afternoon. Note two
things since that mail
- It's conceivable that the context is changing around due to our
interrupting it during a syscall: that whole pc-losering ball of wax
- However, after replacing the sleep call (which calls
select()) with a call to an infinite loop written in C,
we still get floating-point errors reported. So, at least there's a
problem we can work on that doesn't involve system calls - and, who
knows, maybe the syscall problem isn't really a problem anyway.
Nobody really uses EAX for anything, do they?
Oh, and for completeness' sake, the test
The syscall problem indeed wasn't the problem - or even a#
Sun, 17 Aug 2003 03:43:17 +0000
The syscall problem indeed wasn't the problem - or even a
The real problem was that we weren't saving/restoring a pile of
stuff (most immediately obvious gap: floating point modes) that we
should have been. This was fixed by calling
callintolisp(function) instead of function
directly. And a certain amount of messing around with our fake stack
to make it both correct and intelligible to SBCL's backtrace
The non-problem was that during an interrupted select()
call, eax was changing from -514 (as seen by ptrace when the signal
went off) to -4 (as seen in the signal handler). The former is
-ERESTARTNOHAND, the latter is -EINTR. It's kind of interesting that
ptrace() gets to see (what as far as I can tell is) the
kernel-internal value of eax, but I can't right now think of any way
this might be exploited, so oh well.
returntolispfunction (soon to be renamed
arrangereturntolisp_function) is now in CVS.
Having successfully thought myself back into the role of SBCL#
Mon, 18 Aug 2003 12:51:40 +0000
Having successfully thought myself back into the role of SBCL
maintainer on Saturday, I decided it would be nice to fix the
longstanding (well, few-months-old) bug that finalisers don't. This
is actually a symptom of a more general problem: that I removed all
the GC hooks completely because the way we were running them wasn't
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ Command
17849 dan 9 0 150m 72m 896 S 0.0 58.5 10:17.89 gdb
(gdb) info bre
Num Type Disp Enb Address What
9 hw watchpoint keep y (int ) 1079316548
Error evaluating expression for watchpoint 9
Error accessing memory address 0x40551044: No such process.
Watchpoint 9 deleted.
Couldn't write debug register: No such process.
A debugging session is active.
Do you still want to close the debugger?(y or n) y
Detaching from program: /home/dan/src/sourceforge/sbcl/src/runtime/sbcl, process 17967
ptrace: No such process.
It kind of works. It works up until the point that the
pseudo-atomic-interrupted flag mysteriously sets itself without saving
the handler/signal/siginfo etc that is supposed to be saved when a PA
section is interrupted, so we jump to zero and go boom.
But now it really really is time to return to my assault on CLiki
and related stuff, and then investigate programmatic interfaces to Streetmap (which I think may
involve XML somewhere).
I was going to write something here to describe the recent GC#
Fri, 22 Aug 2003 03:15:04 +0000
I was going to write something here to describe the recent GC
rearrangement work. But then I spent a long time on a mail to
sbcl-devel explaining it all anyway. So then I was going to put a
pointer here to the list archive. But then it didn't show up in the
list archive, probably due to mail servers everywhere being hammered
by windows viruses and their associated bounce messages. So I may as
well cut and paste, just to have something in the diary.
If you read sbcl-devel, you'll (eventually) get this twice. Sorry
The stop-theworldbranch is ready for wider testing (anoncvs users,
please be sure you have the latest; version.lisp-expr is
"0.8.2.38.stoptheworld.7"). It's too big a change for 0.8.3
release, but will probably be merged early in the 0.8.4 cycle.
If you have any application that uses threads, please download it and
give it a go, and report progress or lack thereof. If you have any
kind of single-threaded SBCL, I may well have broken that in the
process : if you feel like sorting out the wreckage and
sending/committing patches, that will be a help.
What it does:
1) move from ptrace() to signals for stopping threads at GC time.
This probably makes it easier to port to other systems - except that
we're using a couple of Posix RT signals, which FleaBSD apparently
doesn't have, but I'm sure that can be worked around somehow - and
also means that you can attach strace to sbcl threads without them
dying horribly due to ptrace reparenting larks. Thanks to Gary Byers
for pointing out (some time ago) this way of doing things. I think he
said he got it from the Boehm collector.
2) clean up (or at any rate, rewrite to be differently messy) a pile
of stuff in the signal handling. Sometimes this was just adding
commentary, but also I think the new functions maybedeferhandler and
rundeferredhandler make it a lot easier to write signal handlers
which obey the pseudo-atomic rules - and to know that they're
uniformly obeyed in the existing handlers that profess to observe
them, of course. This also fixes a signal-safety bug in
interrupt-thread (which, sadly, 0.8.3 will ship with, but
interrupt-thread didn't exist at all in 0.8.2, so if there are any
threads users who are insufficiently bleeding edge to be able to
compile their own CVS versions, they probably won't miss what they
3) I wrote last week about return-elsewhere (the new arrangement for
calling Lisp code as a result of signals being handled: see previous
message at http://article.gmane.org/gmane.lisp.steel-bank.devel/1737 )
but I don't think I announced that it was working. It is (though
it's only used for interrupt-thread and control stack exhausion).
Most of this was done on HEAD before the branch, but if you're going
to hack around with C-level signals stuff I suggest you look at the
branched code anyway because the new _defer functions make it easier
to get right. If they're right, at least. Otherwise they make it
easier to blame incorrect operation on me; granted that's a poor
second best, but it preserves your honour at least.
4) move from a dedicated thread for GC which runs no lisp code, to a
system where any thread can collect garbage. The immediate advantage
is that we now have a thread-safe way of running hooks before/after
GC, and the most often asked-for hook is something to run GC
I haven't actually implemented anything to call said hooks yet. It
should be a couple of lines of code, but I thought I'd ask first:
a) there are a couple of hook lists for before/after gc in the system
already. Functions on these lists take no arguments and return
b) CMUCL also has notifiers (or something: I'm going on memory and
it's been a while): these get arguments for the amount of time/memory
spent/saved/wasted/until next gc, etc.
I'm inclined to unify hooks and notifiers in SBCL, retaining the
zero-argument hook signature, and shove any interesting-looking kind
of gc statistics into special variables where calleds could either get
them or ignore them at their leisure. Comments?
:; cvs status version.lisp-expr
File: version.lisp-expr Status: Up-to-date
Working revision: 1.1167.2.6
Repository revision: 1.1167.2.6 /cvsroot/sbcl/sbcl/version.lisp-expr,v
Sticky Tag: stoptheworld_branch (branch: 1.1167.2)
Sticky Date: (none)
Sticky Options: (none)
:; tail -1 version.lisp-expr
New release (0.4) of net-telent-date#
Sun, 24 Aug 2003 02:27:40 +0000
New release (0.4) of net-telent-date. I always feel slightly guilty
about the name of this package: I named it when I was on a bit of a
"all packages should have guaranteed-unique names, and using the dns
is the best way to ensure this" kick, but most of the actual code in
it is in fact lifted from CMUCL, so calling it something with 'telent'
in the name is in a certain light tantamount to passing off. Oh well.
Anyway, new function universal-time-to-rfc2822-date, which attempts
to do local time. It follows the existing practice of decode-universal-time
for its argument list, which essentially means there are only two ways
to use it that don't require a teatowel wrapped around the neck to avoid
dribbling brain on the floor:
- without the optional argument, you get local time
- with 0 as the optional argument, you get UTC (or GMT)
In a spirit of 'release early, release often', I have decided to start#
Sun, 24 Aug 2003 02:56:24 +0000
In a spirit of 'release early, release often', I have decided to start
making new araneida/cliki/etc releases more or less as often as I fix
bugs, except when I definitely know it to be in a broken state. This
is as distinct from my previous approach of only releasing when I was
at least moderately confident that it would work, which meant that I
never released anything
Of course, the Internet (or perhaps NTL) has chosen the occasion of
this decision to break, so
It might also be the impetus I need to hone my release procedure a
cl-ppcre is a portable CL#
Sun, 24 Aug 2003 07:16:35 +0000
cl-ppcre is a portable CL
package providing perl-compatible regexps. There are two things I'd
like to say about it on the basis of ten minutes use
- (asdf-install:install "/home/dan/cl-ppcre.tgz")
1) System-wide install:
System in #P"/usr/local/lib/sbcl/site-systems/"
Files in #P"/usr/local/lib/sbcl/site/"
2) Personal installation:
System in #P"/home/dan/.sbcl/systems/"
Files in #P"/home/dan/.sbcl/site/"
Installing /home/dan/cl-ppcre.tgz in #P"/home/dan/.sbcl/site/",#P"/home/dan/.sbcl/systems/"
[ ... and so it goes ]
Although billed as perl-compatible, that doesn't mean you have to
use the Perl syntax: you can also write regexes as trees. For example
(let ((a '(:CHAR-CLASS (:RANGE #\a #\z)))
(s '(:GREEDY-REPETITION 0 NIL :WHITESPACE-CHAR-CLASS)))
(:sequence ,a ,n ,s ,N ,A ,A)
(:sequence ,A ,N ,N ,s ,N ,A ,A)
(:sequence ,A ,A ,N ,s ,N ,A ,A)
(:sequence ,A ,A ,N ,N ,s ,N ,A ,A)
(:sequence ,A ,N ,A ,s ,N ,A ,A)
(:sequence ,A ,A ,N ,A ,s ,N ,A ,A)))))
- (cl-ppcre:scan postcode-p "w1y 1ha")
That's a regex for UK postcodes (actually, not quite. I should add
the special case for GIR 0AA, which apparently is Alliance &
Leicester Girobank Plc in Bootle). Isn't it just much easier to see
what it does as a tree?
Sometimes I wonder whether the C library maintainers want to actually#
Sun, 24 Aug 2003 22:09:08 +0000
Sometimes I wonder whether the C library maintainers want to actually
discourage programmers from e.g. writing signal handlers.
In glibc 2.3.1 on the 32 bit PowerPC, it was possible to access
machine registers in a signal context (e.g. from a SA_SIGINFO signal
handler) by doing something like
In 2.3.2 this fails with the message
error: structure has no member named `regs'
It looks from a brief inspection of the glibc cvs as though changes to
the ucontext structure were made for compatibility purposes with
ppc64. Which is probably reasonable; can't stand in the way of
progress, Mr Dent. So this code should now be
The problem, of course, is that this code doesn't build on the older
version, which a lot of people (me, certainly, and most other people
probably) are still using. So, this calls for conditional compilation
based on some header feature: icky, maybe, but necessary.
- define GLIBC 2
- define GLIBCMINOR_ 3
Whoever wrote this file obviously subscribed to the (quite sensible,
IMO) point of view that new features were not going to be introduced
in patchlevel releases. Whoever added the 64 bit support, which
breaks our source code compatibility, seems to have quite
different ideas :-(
I suspect we'd disagree on the details#
Sun, 24 Aug 2003 23:48:00 +0000
I suspect we'd disagree on the details. In fact, we'd disagree on
quite a lot of the general approach, never mind the specific details,
if only because I'm quite attached to CL and have already invested
significant time in it (the reader may harbour his own opinion on
the direction of any possible causal relation there). But in general
terms I really do think Tom Lord is onto something with his
thoughts on free software architecture
For a long time, the right strategy for GNU was to build a basic unix
replacement differentiated primarily by licensing. As software goes,
the core of unix is a simple architecture, reflecting its history as a
design first realized by a very small team of people.
Well, that part's done and the strategy won.
Nowadays, the proprietary competition is about databases, and
productivity apps, and browsers, and middleware layers. The software
we're competing against is not like unix: it isn't simple; it wasn't
built by a small number number of people; it's a moving target. It
isn't a tractable project to clone this proprietary software under
If the goal is still "(a) build a free alternative to proprietary
software", then a new strategy is called for: competition on
softwarearchitecture_, not just licensing.
Make your end-users into peers#
Mon, 25 Aug 2003 19:43:26 +0000
Make your end-users into peers
I hope Miles won't mind me excerpting from his private email in
this public place, but I spent long enough editing this reply that
I fel I should get full value by exposing the rest of you foolish
readers to it as well. He wrote
> Just read your latest journal entry regarding Tom Lord's post about the
> direction of free software. It's an interesting idea. Have you had any
> thoughts about what this might look like specifically?
To which I have to admit: no, not really. I think he's identified the
problem; I don't know the solution, but I don't think it's any of the
attempts we've seen so far.
I've read a little by and about Christopher Alexander and the patterns
movement, and what he said about habitability and piecemeal growth
struck a chord with me. The users/inhabitants of a system aren't
expected to be able (or willing) to rebuild it completely, but do want
to customise it appropriately to their needs. And I don't think
that's what we've got in the applications world; we've got
customisation knobs for everything the app designer thought it would
be nice to adjust, and for everything the users have previously
asked to change, but if anyone thinks of something new that they'd
like changed, we're back where we started.
The Unix shell has aspects of the right thing. Your environmental
customisation (~/scripts/frob.sh) is using the exact same tools as the
OS itself (/etc/init.d/frob). It falls down in the large: either the
quoting rules come in and bite you, or the lack of support for any
kind of object that's not a stream of bytes trips you on the way out
and dribbles caustic saliva from its toothless mouth until you
dissolve into a small puddle.
Emacs has aspects of the right thing; most of it's written in Lisp,
and so there's an ecology of stuff built up around it. That's good.
X support (not per se, but the way it's been exposed to Lisp code) has
tended to take it in the wrong direction, and what little I've seen of
the xemacs team suggests that they're wholly misguided. (Disclaimer:
I barely follow xemacs development; I just have the impression of lots
of C programmers and not a lot of consideration for the high-level
picture). Emacs may once have been intended as the basis for a user
interface to the GNU system, but if this was a primary goal I think
rms has largely failed to promote it. And yes, it would help to have
threading, an option for lexical scope, objects, and UI support good
for more than just putting words on the screen.
What's the message that's coming through here? I'm trying to say
that I want the high level design for free systems to start looking
less like application design and more like language design. In my
ideal world you get twenty five points for writing a library, five for
a framework, and only three for an application.
Some of the apps people say (or used to say) "we're not designing
for people like us any more, this is for the end user", but that
implies a power imbalance which I really don't want to be part of. I
want a system that the end-user can participate in, not just one that
they can take or leave. A free software community that's actually a
community, if you like
So I think for the moment the summary is "habitable software", or
"make your users into your peers". It's a hard sell, though:
customisable software in the eyes of business doesn't mean letting the
accountant edit her own startup file, it means getting a bunch of
expensive consultants in to misunderstand the business and give you a
new system that you still don't understand anyway; not automatically a
Good Thing. Ideas welcome
The standard Perl wisdom is that There's More Than One Way To Do It#
Thu, 28 Aug 2003 02:04:21 +0000
The standard Perl wisdom is that There's More Than One Way To Do It.
In Lisp there are often also many ways to do the same thing. At a
low level you'll often see people on comp.lang.lisp or wherever
comparing approaches: debating loop vs do, or the finer points of
format strings, or closures vs objects, or recursive vs iterative
solutions (for the record, tail-recursion is not the Holy
Grail; if the problem is natureally recursively decomposed, use
recursion. Otherwise just write a loop, already. And these debates
just tend to help everyone involved to acquire a more complete
picture of the language.
At a higher level, of course, there are many different strategies
for solving the problem, but where in Perl you might go with that
other well-known saying "the Right Answer is whatever lets you get
your job done" (aside: I'm sure I remember hearing this all the time;
now I can't find a single instance of it on Google. Maybe I'm
assigning too more pragmatism to the Perl Way than I ought; sorry,
guys), in CL you typically (at least, I typically) spend a bit more
thinking time upfront to decide on an elegant solution.
I appear to be suffering choice paralysis.
Weekend spent on Araneida hacking, which somehow ended up being#
Mon, 01 Sep 2003 02:58:02 +0000
Weekend spent on Araneida hacking, which somehow ended up being
SBCL hacking. Two motivations:
- For the new version of the Local Food Directory (a
CLiki application, if it wasn't immediately obvious from looking at
it) we're going to be doing interesting things like tying into Streetmap for postcode
searches and suchlike. It's also prettier, which is nice if you like
that kind of thing.
The practical impact of tie-ins with an external server, though, is
that our latency for replying to requests now depends on circumstances
beyond our control. Most (all) of the Araneida services so far are
written so that we have some fairly good idea of how long it'll take
to answer a request: we only talk http to a localhost proxy instead of
slow remote clients; if we send mail, we send it to an smtp listener
on the local machine; and our database queries, on the sites that use
databases, are mostly fairly well tuned. But, remote hosts. Can't do
much with that. Had better try this threading stuff for real, then.
- The users of Araneida, of which there seem to be an expanding number no
matter what obstacles I throw up in their way (making them all install
SBCL was going to be a pretty good way to make them go away, I
thought, but still apparently Not Enough) are fond of pointing out
that the export-server stuff is a bit weird at best. I concur.
It made sense once upon a time.
In brief, we add a new class
http-listener (concrete subclasses
threaded-http-listener and serve-event-http-listener)
which represents a single endpoint (a host/port combination) and
dispatches all stuff that comes in on that endpoint to a handler
(defclass http-listener ()
((handler :initform *root-handler* :initarg handler
(address :initform #(0 0 0 0) :initarg :address
(port :initform 80 :initarg :port :accessor http-listener-port)
Many listeners may dispatch to the same handler, and the handler may
be a dispatching handler if it likes. There still needs to be some
provision somewhere for lying about the hostname (as in, your external
server address is foo.com:80/ but your araneida is actually on :8000)
and a place to hang random extra bits that would be useful for
generating apache httpd.conf segments (like where on the disk to find
ssl certificates, etc), but it looks good so far.
While doing this, add some dynamic guess-how-many-processes-we-need
stuff to adjust the number of serving threads based on load, slap it
all back together and hammer it a bit with apachebench.
Oops. Not literally "Oops" in the sense that a Linux kernel hacker
would know it, but EFAULT from accept() anyway, which is kind
of analogous for a user program.
sb-bsd-sockets:socket-accept calls accept with the
contents of a suitably sized Lisp vector as the second argument (the
sockaddr). To make sure this doesn't get relocated between our taking
the address and calling out, we wrap it in without-gcing to
disable gc for the duration. This is actually a really bad idea
because all the idle threads block in select(), so we can't GC unless
we're really really busy; somewhat perverse. And, just to be awkward,
doesn't always work either. For some reason that I haven't yet found,
it is possible to have a GC happen during without-gcing.
I shall spare you the story of my VOP-writing and GC
staring-at experience on Sunday afternoon, but the upshot is that
It should be noted that although I started writing this entry at
whatever ungodly time it says, I finished and uploaded it at around
midday on Monday
That was very nearly the right answer#
Mon, 01 Sep 2003 21:22:14 +0000
That was very nearly the right answer. In fact
- there are a couple of places that write-protect pages, so both
need to check the dont_move bit
- GC wipes out dontmove on all pages at the start of GC,
before running preservepointers().
preservepointers only looks at the 'from' space (after all,
we're not moving objects anyway unless they're in in fromspace), so
when we see these pages again later we no longer have them specially
marked, so we write-protect them as normal. Wrong. Having realised
the problem, the solution is simple: only reset dontmove on
fromspace pages instead of on all pages.
:; /usr/sbin/ab -c5 -n10000 http://xxxxxxxxxxxxxxxxxxx:8009/Welcome
Server Software: Araneida/0.74
Server Hostname: xxxxxxxxxxxxxxxxxxx
Server Port: 8009
Document Path: /Welcome
Document Length: 2796 bytes
Concurrency Level: 5
Time taken for tests: 190.112 seconds
Complete requests: 10000
Failed requests: 0
Broken pipe errors: 0
Total transferred: 29582958 bytes
HTML transferred: 27962796 bytes
Requests per second: 52.60 [#/sec] (mean)
Time per request: 95.06 [ms] (mean)
Time per request: 19.01 [ms] (mean, across all concurrent requests)
Transfer rate: 155.61 [Kbytes/sec] received
Connnection Times (ms)
min mean[+/-sd] median max
Connect: -10 0 12.0 0 848
Processing: 7 42 104.7 17 1998
Waiting: 0 41 104.1 16 1998
Total: 7 42 105.9 17 1998
Percentage of the requests served within a certain time (ms)
100% 1998 (last request)
10000 requests later with no problems, and i think we've got this