5 ms·

Netflix's async sendfile now in FreeBSD-current

179 points by drewg123 11y ago

drewg123 11y ago
Slides from a presentation about async sendfile can be found at: http://www.slideshare.net/facepalmtarbz2/new-sendfile-in-english http://www.slideshare.net/facepalmtarbz2/new-sendfile-in-eng...
- vive-la-liberte 11y ago
  Slide 27/36, aka. slide 18/23, shows a type of graph which I have also seen in the Google Chrome Dev Tools as well as a couple of other places. Someone told me once the name of that kind graph but I've forgotten what it was. I've never learned how to read that kind of graph. So, if someone would be so kind, please tell me what it's called and how to read it.
  - bithive123 11y ago
    http://www.brendangregg.com/flamegraphs.html http://www.brendangregg.com/flamegraphs.html
    - vive-la-liberte 11y ago
      Thanks :)
    - tomjakubowski 11y ago
      Great resource! Thank you.
  - revelation 11y ago
    They call it a flame graph and what you are seeing are call stacks. X axis is time, Y axis is call stack depth. The very bottom layer is the function you are analyzing, ever layer above is a function called by the one directly below it.
    - vive-la-liberte 11y ago
      Thank you. Very succinct explanation. I like that.
    - jberryman 11y ago
      > X axis is time That's not correct from what I'm reading.
      - michael_h 11y ago
        The span on the x-axis is the amount of time spent in a function, but not the passage of time left-to-right.
      - revelation 11y ago
        If you are sampling the stack at equidistant points in time (or, sampling theorem and all, fast enough) and then determine the width on the basis of "seen in fraction of samples", that's pretty close to time. (timespan if you want)
    - michael_h 11y ago
      I down voted you because I'm on a phone and my thumb is a bit bigger than the voting triangles - apologies.
  - wging 11y ago
    It's a flame graph or flame chart. I found this video explaining how to use them: https://www.youtube.com/watch?v=g0g4ML4nhPg https://www.youtube.com/watch?v=g0g4ML4nhPg I think the basic idea is: say you have some code like this. function a() { // 6 ms b(); // 3 ms c(); // 3 ms } Then you might have a flame chart that looks like this: [-b-][-c] [---a---] Essentially you're decomposing the time we spend in a() into its constituent pieces b() and c().
    - brendangregg 11y ago
      essentially, yes, but: flame graphs: x-axis is sample population (or event time), alphabetical sort on function names to maximize merging flame charts: x-axis is the passage of time
ihsw 11y ago
I love how the commit day is the same as the last one -- January 6. I'll be damned if C doesn't look like arcane magic to me, I can grok some/most of it but fitting it all in my head would take a herculean effort. Maybe it's system's programming but either way it makes my brain melt.
- jrcii 11y ago
  Far be it from the power of my single, small protesting voice to change the tide of a culture, but I wish we could discontinue the use of the word grok. The sound is aesthetically offensive somehow, and yet adds nothing to the synonyms: comprehend or understand. Its proponents claim it implies a /complete/ understanding, so is more specific. Yet "I understand" does not imply an incomplete understanding. Furthermore the implication of completeness is a weak one, this is proven by how quickly and easily even that small value is neutralized when, for example, the parent said, "I can grok some/most of it." If we should take this to mean, "I can completely and comprehensively understand some or most of it," is that meaningful or truly the parent's intent? Even if it were, does it add to, "I can understand some or most of it"? I would speculate that the reason a word for "completely understand" hasn't already made its way into the English lexicon after hundreds of years is because it's unnecessary, and further that its use within the IT community is motivated not so much by the desire for precision in communication as by a desire to be perceived as a savvy member of the community.
  - barbs 11y ago
    I, for one, like it because it's only one syllable, but it's obvious that brevity isn't of importance to you :)
  - melted 11y ago
    To properly grok the word "grok", you need to read "Stranger in a Strange Land" by Robert Heinlein. Quite possibly the best sci-fi book ever written.
    - atdt 11y ago
      Thou art exaggerating.
akkadmed 11y ago
sendfile(1) was taken from Microsoft Windows.

179 points by drewg123 11y ago

Slides from a presentation about async sendfile can be found at: http://www.slideshare.net/facepalmtarbz2/new-sendfile-in-english http://www.slideshare.net/facepalmtarbz2/new-sendfile-in-eng...

vive-la-liberte 11y ago
Slide 27/36, aka. slide 18/23, shows a type of graph which I have also seen in the Google Chrome Dev Tools as well as a couple of other places. Someone told me once the name of that kind graph but I've forgotten what it was. I've never learned how to read that kind of graph. So, if someone would be so kind, please tell me what it's called and how to read it.
- bithive123 11y ago
  http://www.brendangregg.com/flamegraphs.html http://www.brendangregg.com/flamegraphs.html
  - vive-la-liberte 11y ago
    Thanks :)
  - tomjakubowski 11y ago
    Great resource! Thank you.
- revelation 11y ago
  They call it a flame graph and what you are seeing are call stacks. X axis is time, Y axis is call stack depth. The very bottom layer is the function you are analyzing, ever layer above is a function called by the one directly below it.
  - vive-la-liberte 11y ago
    Thank you. Very succinct explanation. I like that.
  - jberryman 11y ago
    > X axis is time That's not correct from what I'm reading.
    - michael_h 11y ago
      The span on the x-axis is the amount of time spent in a function, but not the passage of time left-to-right.
    - revelation 11y ago
      If you are sampling the stack at equidistant points in time (or, sampling theorem and all, fast enough) and then determine the width on the basis of "seen in fraction of samples", that's pretty close to time. (timespan if you want)
  - michael_h 11y ago
    I down voted you because I'm on a phone and my thumb is a bit bigger than the voting triangles - apologies.
- wging 11y ago
  It's a flame graph or flame chart. I found this video explaining how to use them: https://www.youtube.com/watch?v=g0g4ML4nhPg https://www.youtube.com/watch?v=g0g4ML4nhPg I think the basic idea is: say you have some code like this. function a() { // 6 ms b(); // 3 ms c(); // 3 ms } Then you might have a flame chart that looks like this: [-b-][-c] [---a---] Essentially you're decomposing the time we spend in a() into its constituent pieces b() and c().
  - brendangregg 11y ago
    essentially, yes, but: flame graphs: x-axis is sample population (or event time), alphabetical sort on function names to maximize merging flame charts: x-axis is the passage of time

ihsw 11y ago

I love how the commit day is the same as the last one -- January 6. I'll be damned if C doesn't look like arcane magic to me, I can grok some/most of it but fitting it all in my head would take a herculean effort. Maybe it's system's programming but either way it makes my brain melt.

jrcii 11y ago
Far be it from the power of my single, small protesting voice to change the tide of a culture, but I wish we could discontinue the use of the word grok. The sound is aesthetically offensive somehow, and yet adds nothing to the synonyms: comprehend or understand. Its proponents claim it implies a /complete/ understanding, so is more specific. Yet "I understand" does not imply an incomplete understanding. Furthermore the implication of completeness is a weak one, this is proven by how quickly and easily even that small value is neutralized when, for example, the parent said, "I can grok some/most of it." If we should take this to mean, "I can completely and comprehensively understand some or most of it," is that meaningful or truly the parent's intent? Even if it were, does it add to, "I can understand some or most of it"? I would speculate that the reason a word for "completely understand" hasn't already made its way into the English lexicon after hundreds of years is because it's unnecessary, and further that its use within the IT community is motivated not so much by the desire for precision in communication as by a desire to be perceived as a savvy member of the community.
- barbs 11y ago
  I, for one, like it because it's only one syllable, but it's obvious that brevity isn't of importance to you :)
- melted 11y ago
  To properly grok the word "grok", you need to read "Stranger in a Strange Land" by Robert Heinlein. Quite possibly the best sci-fi book ever written.
  - atdt 11y ago
    Thou art exaggerating.

akkadmed 11y ago

sendfile(1) was taken from Microsoft Windows.