Viewing profile — evan_miller

You're missing something very significant: Compilation jobs involve a lot of forking. Forking, memory accesses, and TLB differences across various VM architectures can have an enor…

The semantics for write(2) and mmap(2) differ. Neither can be used to implement the other in full. It's possible to have access patterns which don't demonstrate the efficiencies of…

Additionally they may also legally earn money. How else would children appear in movies? The particulars vary by state, but here's a quick glimpse as to the federal perspective: ht…

It's actually -ne, perhaps with -a if one wants awk-style field splitting of lines. -l modifies the output record separator (makes print append \n)

Have you tried disabling only defrag? The performance issues I'm familiar with are generally related to defrag running at allocation time. I would be curious to see your results wh…

Ah, thanks for your feedback. I'm never sure how much detail I should dive into. I will add more next time. I'll answer them here just for practice :) Recall, this is a problem in …

The fsync() is implicit behavior of the glog framework for Go. We didn't actually want it.

Yes. I haven't done anything with a log-structured FS. I have only played around with conventional filesystems.

Sort of. The catch is that even a very small write, say just a few megabytes, can drastically change the cost of an fsync(). On my test aws VM even writing just 4 megabytes one tim…

Not recently, no. I do know that a journaled filesystem can exacerbate this sort of problem as it can make extra work. For example: http://lwn.net/Articles/328363/ In a few cases i…

With fsync() taken out of the equation this is essentially how a naive logger operates. The linux page cache plays the role of shared memory and only under rather heavy contention …

Hi, post author here. The slight difference in i/o (specifically: writes) was the trigger. I talked a little more about that here: http://corner.squareup.com/2014/09/logging-can-be…

Hi, post author here. I didn't make it as clear as I could have, but the difference is that the problematic system had an unrelated process creating slightly more writes. I sort-of…