6 ms·

From the github issue linked elsewhere in the thread: > KiB Mem : 16431044 total, 215356 free, 15894868 used, 320820 buff/cache That's... not a lot of hea

by xmodem 5y ago

From the github issue linked elsewhere in the thread: > KiB Mem : 16431044 total, 215356 free, 15894868 used, 320820 buff/cache That's... not a lot of headroom. I'm impressed their OS is paired down to the point they can run in this state with this being the only pathology.

trollied 5y ago
Looks like they run a known [java] workload constantly. The java heap is allocated at startup (and is used for dynamic allocations). I don't see why they shouldn't be doing this. They also have a ridiculous amount of instrumentations and monotoring, so if it was a problem it would have been identified long ago.
- necovek 5y ago
  This was a constant source of problems with any Java app I've ever used. Why can't heap be dynamically sized in cooperation with the OS JVM is running on? I imagine it's some early backwards-compatibility JVM restriction, but it is so annoying.
  - mcculley 5y ago
    Free memory is wasted memory. Applications that cache data have to do it on the heap. Yes, there should be a way for the system to coordinate usage of cache/free memory and coordinate with a VM’s GC. Until we have that, big apps will exhibit the aforementioned memory footprint.
    - necovek 5y ago
      I am not talking of the netflix case from the OP, but rather of the general case where you are likely to have multiple services on a single host. Just imagine if a couple of them were Java-based: you'd have to do figure out how much is the maximum needed for each of those and sum it up and ensure the server has that much memory even if they are unlikely to all need it at the same time: if we are talking about waste, that's wasteful to me. Even in a more modern setting with containers, you'd have similar issues.
  - xmodem 5y ago
    Java can be tuned to release freed memory to the OS: https://www.geekyhacker.com/2019/01/04/jvm-does-not-release-memory/ https://www.geekyhacker.com/2019/01/04/jvm-does-not-release-...
- xmodem 5y ago
  I didn't mean to imply that it was a problem or that they shouldn't be doing it - more that i'm envious of the operational chops to pull it off.
Dylan16807 5y ago
Skip the percentages for a second. >300MB of cache and >200MB free is a lot of memory! That's enough memory to run an entire server without breaking a sweat. Instead of calling proper function impressive, I'd be quite upset if getting that low causes problems.

by xmodem 5y ago

trollied 5y ago

Looks like they run a known [java] workload constantly. The java heap is allocated at startup (and is used for dynamic allocations). I don't see why they shouldn't be doing this. They also have a ridiculous amount of instrumentations and monotoring, so if it was a problem it would have been identified long ago.

necovek 5y ago
This was a constant source of problems with any Java app I've ever used. Why can't heap be dynamically sized in cooperation with the OS JVM is running on? I imagine it's some early backwards-compatibility JVM restriction, but it is so annoying.
- mcculley 5y ago
  Free memory is wasted memory. Applications that cache data have to do it on the heap. Yes, there should be a way for the system to coordinate usage of cache/free memory and coordinate with a VM’s GC. Until we have that, big apps will exhibit the aforementioned memory footprint.
  - necovek 5y ago
    I am not talking of the netflix case from the OP, but rather of the general case where you are likely to have multiple services on a single host. Just imagine if a couple of them were Java-based: you'd have to do figure out how much is the maximum needed for each of those and sum it up and ensure the server has that much memory even if they are unlikely to all need it at the same time: if we are talking about waste, that's wasteful to me. Even in a more modern setting with containers, you'd have similar issues.
- xmodem 5y ago
  Java can be tuned to release freed memory to the OS: https://www.geekyhacker.com/2019/01/04/jvm-does-not-release-memory/ https://www.geekyhacker.com/2019/01/04/jvm-does-not-release-...
xmodem 5y ago
I didn't mean to imply that it was a problem or that they shouldn't be doing it - more that i'm envious of the operational chops to pull it off.

Dylan16807 5y ago

Skip the percentages for a second. >300MB of cache and >200MB free is a lot of memory! That's enough memory to run an entire server without breaking a sweat. Instead of calling proper function impressive, I'd be quite upset if getting that low causes problems.