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OLS continued, continued

For some reason I woke up around 5:30 this morning and had trouble getting to sleep again, so I felt like I was sleep-walking through most of the day.

But I still managed to make it to three talks in the morning (on lguest, Zumastor, and SMB2), and get some long-delayed work done in the afternoon.

Afterwards I spent some time browsing at Chapters and Librarie du Soleil, where I picked up Trondheim's "La Couleur de l'Enfer", and Rabagliati's "Paul à la Pêche". The bookstore clerk was extremely enthusiastic about the latter, which follows a couple others ("Paul en Appartement", and "Paul a un Travail d'Été") that are wonderful. The first time I came out to OLS, the day after it ended, I picked up "Paul en Appartement" on a whim and took it down to the park overlooking the locks, just where the canal empties into the river, and had an extremely pleasant afternoon sitting on a park bench not believing my luck at having come across the book.

I stopped by a laundry near my B&B on my way back, but saw that it was about to close in a half hour, so decided to leave it tomorrow, and headed to the Thai restaurant a block away instead, where I had a good green curry and some mango ice cream before heading back "home" and turning in.

OLS continued

Breakfast was good, and my ride in went well. There'd been some brief overnight rain, and the temperature was down to something more comfortable.

The first talk was a bunch of statistics about kernel development--rate of change (high!) number of developers (lots, and increasing!). The data was kind of fun to look at, but didn't seem very well thought-out to me; for one thing, it wasn't entirely clear what they were trying to figure out, or how the numbers might help. And for another, I felt like it fell into the usual quantity-over-quality trap: if they'd spent more time carefully examining a few randomly chosen examples, instead of trying to collect huge gobs of (probably inaccurate) aggregate statistics, they might have had more interesting results.

There was a giant chart on the back wall of the room with a bubble for each kernel developer and lines connecting any two kernel developers that had consecutive sign-offs on some patch. They were collecting autographs next to each developer's name. I found mine, but couldn't follow any of the lines--the chart wasn't really printed with sufficient resolution.

After that there was an interesting talk by someone who'd examined performance of some big "enterprise" (I think that means Oracle) workloads on a machine with a lot of processors--four quad cores. The problem here is that access to the computer's RAM is really slow, so each processor has to have a cache of recently used memory. But then those caches have to be kept consistent--if a write to memory on one processor is followed by a read of the same address on another processor, then you have to make sure the read sees the new value stored at that address. This is slow, so if it happens a lot, performance can decrease dramatically. So you try to make sure that different processors are mostly working on different parts of memory, instead of bouncing around the same piece of memory from one cache to another. The speaker seemed to have some quite nice tools that would show exactly which pieces of which data structures were getting bounced around to much, and which code was responsible.

I didn't really pay as close attention to anything else that day.

Dinner was at a nearby pseudo-Irish pub, with a few selinux ("security enhanced linux") and NFS people. There's some interesting work to be done to make the two systems play well together. By the end of dinner I felt like I understood at least a few basic things about selinux.

I couldn't get my laptop to work with the conference wireless network, but found some ethernet ports and managed to get some routine work done in gaps during the day.

I was idly hoping to make it to one of the Ottawa Jazz Festival events in the evening, but by the end I was tired and ready to go back.

And the ride home was fine again. I'm feeling a little more comfortable on the rental bike.

Ann Arbor to Ottawa

Monday we met at Top of the Park to see a couple songs before heading home. I was up fairly late packing for the next morning's trip to Ottawa for the Ottawa Linux Symposium.

The trip was routine: my ride to the airport picked me up at 8, the flight left at 10:15, and once in Ottawa I hopped on the bus downtown; by 12:30 I was sitting down for lunch in the Byward Café. The conference wasn't starting till the next day, but I registered and spend a little time book-shopping. Is it my imagination, or has the Francophone bookstore in downtown Ottawa (Librarie Du Soleil) just gotten a comic-book buyer with taste closer to my own?; this year they have a zillion things I'd love to read. Some restraint will be required to stay within the limits of my backpack (my only luggage on this trip) and my budget.

I'm staying at a B&B that's maybe a couple miles south of downtown--thanks perhaps to Canada day on Sunday, most closer places were filling up by the time I looked. So I figured it'd be fun to rent a bike for my commute. I wonder what the university will say when I give them the bill for that? I know they'd cover a car in the same situation. The bike is a so-called "comfort" bike, which I'm finding a little uncomfortable. But it works. I was surprised that they didn't include lights (or even reflectors)--that seems like a dumb omission if they're renting out bikes overnight--but they had some cute LED headlights and taillights for very cheap.

I rode down the canal a little ways, found a tree to sit under, and read a new acquisition, "Inventaire avant Travaux", the sixth in Dupuy and Berberian's "Monsier Jean" series. I really love the previous albums in the series, so though this one was well done, it wasn't really up to my expectations. I felt like it revisited a lot of ideas they'd covered before without advancing the story much.

I had a beer and some pizza at the pre-event pub night, then headed to the B&B around 9:30. They had a key waiting for me in a box outside, and I found my room without any trouble.

Today was the first day of the conference; my short bike ride in was fine, though the weather's been very hot and humid, and I arrived a little sweaty.

My limited patience for talks ran out by the afternoon, but I managed to learn a couple interesting things on the way. I got both lunch and dinner in the food court of the mall attached to the conference center, so I basically spent the whole day in the mall.

I left for the B&B a little earlier than last night, so got a chance to catch up on a little work (and on this blog!). But now it's almost midnight and well past time I put myself to bed with a comic and read myself to sleep....

mimes on sticks

Sara's come down with my cold, now that I'm almost over it. Thursday night we both went straight home. We tried watching the beginning of "The Prestige". The beginning introduces a bunch of characters all at once, with scenes that are wildly out of chronological order, coming from at least 4 different points in the story. The dialog's a little hard to follow at points too. So it wasn't the best thing to watch over dinner. Sara said she was too tired after about 20 minutes. I ended up watching the rest on my own, finishing it last night after we got home from Top of the Park.

Top of the Park last night featured "Strange Fruit", an Australian group that doing a sort of mime show to music on top of tall swaying polls. It was visually very striking, though I don't know how long it would stay interesting. The choice of name seems a little odd, since the first thing it makes me think of is the Billy Holiday song.

We also saw a bluegrass band and the first set of two by Bugs Beddow before we left.

summer continued

Weather was good for Top of the Park saturday night, and we enjoyed Nomo, though I with my cold I wasn't feeling too energetic.

So Sunday I stayed home and did some reading and a bit of house cleaning.

I've been doing something like full days at work this week, but not really concentrating very well. I manage to get a few things done each day, but feel like I waste more time than I use.

Tuesday night we saw Jeremy Kittel, an Ann Arbor fiddle champion who's since gotten a music degree at U.M. and moved to New York. It's sort of funny to see someone growing up on stage like that.

And tonight we met there again for a while, watched the second band with Dave for a little while, then caught the 9pm bus home.

Our weekly social event at work is Wednesday morning donuts. The main problem with it since I've been there is that the donuts have been terrible. The bagels, too. I don't get it--every street corner here seems to have some chain that churns vast quantities of perfectly fine bagels, so how hard can it be? How can you manage to be in the business of selling bagels and yet not manage to produce something that tastes even approximately like one? Anyway. We changed suppliers last week. Everything's much better now. I no longer stand by the baked goods saying "am I really so hungry that I must eat one of these? Which would be the least disgusting?"

I had a good talk with Chuck over lunch today about the delegations work I've been having one of our interns do. He seemed really interested, and had some good suggestions. It'll be interesting to see where that goes.

summer cold

Wednesday night I hacked up an attempt at a git-diff that stat's multiple files in parallel. It's a definite improvement--down to 3 and a half seconds for "git diff" on a linux kernel tree, from 12 seconds or so. But that's still long enough to be annoying. I haven't tried to figure out where the time's going.

A cold crept up on me over the last couple days, and now I'm feeling a little slow. I worked a little over a half day today and managed to get a few things done. After work I stopped by the "bike fest" on Main. The south end had a ramp set up with some guys taking turns shooting into the air and doing fancy tricks. The north end had a bike with a blender attached where kids were lined up to make their own smoothies. In between there was an obstacle course, a track stand contest, and tents for miscellaneous local organizations and bike shops. There were a lot of people, and a lot of bikes, out. Looked like a success. I didn't get as far as the "green fair" on the north end up main. Usually it seems to be about cars, for some reason.

This was also the first night of Top of the Park. And maybe something else was going on downtown too--it seemed unusually busy. But I wasn't feeling up for anything more, so I just caught the next bus home. I'm hoping I'll be feeling better tommorow, as there's an excellent band ("nomo") playing at Top of the Park tommorow night, which includes a trumpet player who used to live upstairs from us.

movies, stat latency

It's all Jon Johansen's fault. Without him, I wouldn't be able to watch the DVD's I borrow from the library. Now I get home and expect to be entertained every night. Just in the last week:

  • L'enfer: Watch a guy slowly go nuts. I think I prefer a plot that's not one long straight line.
  • Fierce Creatures: It has some pretty funny ideas, but just not nearly enough. In places where "Noises Off" would have a surprising event every second, "Fierce Creatures" would have a bunch of people running around looking frantic.
  • Earth Girls are Easy: OK, this was more fun, though honestly I'm not sure I'll remember it a week from now.

I should read more. In fact, our book group meets tomorrow to discuss "Flow My Tears", and I only read it once fairly quickly a couple weeks ago. I should give it another look before tomorrow night's meeting.

Sara and Paul went birdwatching Saturday morning. I couldn't see getting up before 7am just to look at some birds. But I guess it was quite the morning for it--when I met them for breakfast afterwards they were full of stories of baby swans, vultures, bird nests, and more.

The version control system we use for kernel work, "git", has a problem when running on an NFS filesystem--it detects when files change by calling stat() on them and looking for differences in modification time, size, inode number, etc. That means it can skip having to examine the data of unchanged files, but it still requires stat'ing every file in your working directory--and the linux kernel source has over 20,000 of them. The average ping time to my NFS server is about .2 milliseconds, so a round-trip to the server to request stat information will take at least that long. That means the whole tree will take at least 20000*.0004 = 4 seconds. In practice it ends up being over 10 seconds. A lot of git operations require this, so the delay gets really annoying. On a local filesystem, by contrast, the time is less than a quarter-second, once you've done it once (and the operating systems has cached all that stat data in memory).

NFS does some caching too, but to make sure that it notices file changes made by other clients it has to go back to the server every now and then. And you can tell it to do that less frequently, but then it becomes annoying when you use two clients at once and have to wait for changes made on one to be noticed on the other.

One possible fix is to make the server give out delegations more aggressively--a delegation allows the server to tell the client when a file changes, instead of making the client ask all the time. Thanks in part to a bright intern that's been learning his way around the server code, I think I'll have some help with that.

Another approach is to teach git to do those stat's in parallel, instead of sending all 20-thousand-some requests sequentially. That was my project for Sunday, but I didn't end up getting any further than finding the spot in the code that I'd need to modify to make it work. Maybe next weekend. This is sort of a hobby project, so I'm mostly ignoring it during the week.

home for a day

I was woke up earlier than usual with a stomach on fire, sent email saying I'd be home sick for the day, then tried to nap for the rest of the morning. A few hours later, I was fine. Maybe I ate something bad. So I did a little work from home in the afternoon, but had trouble concentrating.

Last night we watched the last half-hour or so of "Lage Raho Munna Bai", a movie that turned out to be much better than its ludicrous premise might suggest. Tonight we watched "Funny Face", which I expected to be good but wasn't. It had Fred Astaire and Audrey Hepburn in it, and that's about all you could say for it--they both did better elsewhere. I guess it did have its moments. The portrayal of hip intellectual life in Paris is bizarre.

I have a ton of work to get done tommorrow. Hopefully I'll be feeling in better mental shape.

rainy weekend

Sara noticed recently that the Peonies in the Arb were in bloom, so we'd planned a picnic in the peony garden. But the weather didn't cooperate. Instead we juggled on the Diag for a while, then made a dash indoors to the nearby chemistry building atrium, then had some food at pizza house, then finally (the rain having mostly subsided) walked around the peony garden for a while.

Pizza House is popular and ever-growing--word has it it's now the largest restaurant in ann arbor--but I'm not completely sure why. The food is usually OK, but nothing special. The prices are mostly reasonable, but it's not really cheap either. They seem to be in a state of permanent confusion--this time they told us there was nobody upstairs, when a later phone call revealed that some of our friends had already been seated there--then they got two out of seven orders wrong, and there were a few other minor hassles. I'm also annoyed that they consistently refuse to advertise their drink prices--if you want something, you either just order and hope, or ask someone (who usually has to go back to the kitchen to get the answer).

At least they didn't serve any glass in our food, which is what happened (with this same group of friends) a few years ago. I have no idea why we still go there.

Anyway, the peonies were nice. Afterwards we watched "noises off", which was more fun than I expected, though it's a bit frantic and I was a too tired to really keep up with every twist.

Sunday I had dinner at a former citi student's house with a couple other citi people.

Sara and I have also been watching "Lage raho munna bhai", a comedy about a gangster driven to become a follower of ghandi by love of a radio personality. It's actually a lot better than I expected.

Today I took care of my laundry and a few other chores in the morning. But it ended up stretching into the afternoon, and here I am at work late in the day, writing about my weekend. So I'm just writing off today as vacation. The current job offers more vacation than I use, so it's been piling up anyway.

doctors and students

Peter's student Jiaying defended Tuesday morning; total audience: four committee members and me. Her talk was actually pretty good, but they have this odd rule about the questioning occurring between only the committee and the student which meant I probably missed the interesting part. I should have protested.

I juggled a little on the diag after work.

The last couple nights, Sara and I watched the first two episodes of the "new" (except, there's a newer one now maybe?) Doctor Who. I never watched the original, really, but to me this seemed to have a lot of the same flavor--despite the new effects technology, it still feels like most of the aliens have socks on their heads, and the second episode depended on a countdown to build suspense. They weren't really funny enough to make it worthwhile to me.

Today I spent some more time with our interns, getting one started on a new project, and trying out their distcc setup. It was fun.


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