Mtime comparison considered harmful (2018)
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Mtime comparison considered harmful (2018)
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Re: Mtime comparison considered harmful (2018)
#2apropos
> Linux added an O_NOATIME
!!Con 2016 - How I fixed UNIX atime! With 10 lines of code and feminism!!! By Valerie Aurora https://www.youtube.com/watch?v=fHjsdyN4UK0
Re: Mtime comparison considered harmful (2018)
#3The title should be: “I don’t like Mtime comparison. Here’s why.”
If your name is Dijkstra and it’s 1968 feel free to use the phrase “considered harmful”, otherwise use plain language.
Re: Mtime comparison considered harmful (2018)
#4apropos > Linux added an O_NOATIME !!Con 2016 - How I fixed UNIX atime! With 10 lines of code and feminism!!! By Valerie Aurora https://www.youtube.com/watch?v=fHjsdyN4UK0
I suspected this post was generated bot spam given the name of the convention and how most discussions about feminism go on the Internet but I have to say that the talk was interesting and I am glad I watched it.
Thank you for posting it.
Re: Mtime comparison considered harmful (2018)
#5Weird that there is such detailed technical information alongside this statement:
> And anyway, purists might argue that the "content" of a directory doesn't change when the files it points to change; the content is merely a list of filenames and inode numbers, after all, and those stay the same, no matter what happens inside those inodes. Purists make me sad.
Or maybe Unix makes the author sad? You can’t wish the OS into doing something different with directory files when the set of contained files has not changed (but a file was modified) so that these Make troubles could be handled differently.
Am I missing something?
Re: Mtime comparison considered harmful (2018)
#6The title should be: “I don’t like Mtime comparison. Here’s why.” If your name is Dijkstra and it’s 1968 feel free to use the phrase “considered harmful”, otherwise use plain language.
Anti-considered-harmful consided harmful.
What's wrong with the usage? It is short and concise.
Re: Mtime comparison considered harmful (2018)
#7apropos > Linux added an O_NOATIME !!Con 2016 - How I fixed UNIX atime! With 10 lines of code and feminism!!! By Valerie Aurora https://www.youtube.com/watch?v=fHjsdyN4UK0
That talk is about the "relatime" mount option, not the O_NOATIME open() flag. The O_NOATIME open() flag was added following the semantics described in the glibc manual (https://www.gnu.org/software/libc/manual/html_node/Operating... ); I don't know where these semantics came from, my guess (given that it is glibc and O_NOATIME is described as a GNU extension) is that these semantics came from Hurd, though I haven't checked. These semantics aren't ideal (you need extra code to retry without the flag if it fails with a permission error, or you have to open() without the flag and add it later with fcntl(), both cases requiring to an extra system call), if it were added today it probably would have simpler semantics.
(Source: I wrote the patch which added O_NOATIME to the kernel, based on an older patch which didn't get in, see https://lkml.iu.edu/hypermail/linux/kernel/0406.1/0894.html and https://lkml.iu.edu/hypermail/linux/kernel/9811.2/0118.html)
Re: Mtime comparison considered harmful (2018)
#8The title should be: “I don’t like Mtime comparison. Here’s why.” If your name is Dijkstra and it’s 1968 feel free to use the phrase “considered harmful”, otherwise use plain language.
Anti-considered-harmful consided harmful. What's wrong with the usage? It is short and concise.
"Short and concise" isn't much praise. If I wanted something short and concise, I could say "is bad", which is probably both more concise and more honest. "Mtime comparison is bad" is more clear and more concise.
"Considered harmful" is misleading because the passive voice suggests some kind of general consensus which usually doesn't exist.
Re: Mtime comparison considered harmful (2018)
#9I really do think it's unfortunate that the OS cannot keep something like a "write count" for each file. That would be enough. Possibly it would even be good enough to know the number of times a file had been opened for writing.
Re: Mtime comparison considered harmful (2018)
#10The title should be: “I don’t like Mtime comparison. Here’s why.” If your name is Dijkstra and it’s 1968 feel free to use the phrase “considered harmful”, otherwise use plain language.
Anti-considered-harmful consided harmful. What's wrong with the usage? It is short and concise.
Who considers it harmful? Some jerk who uses the royal "we" on themselves?
The issue with the phrase is, that it is hopelessly overused also for things that are purely subjective or way to general.