5 ms·

512GB RAM/2500 containers is still 500MB per container. In former days™ this was enough for a computer to run a complete desktop environment with a web browser

by ktpsns 7y ago

512GB RAM/2500 containers is still 500MB per container. In former days™ this was enough for a computer to run a complete desktop environment with a web browser and 20 tabs open (source: I had a PC with physically 500MB RAM). Is this really the limit for such a decent equipped machine? (I guess a server grade 48 cores, 512GB RAM should be less then 5kEUR nowadays)

jjeaff 7y ago
>512GB / 2500 is still 500mb per container Am I missing something? 512gb / 2500 is around 200mb per container.
- Mirioron 7y ago
  I think he miscalculated. His point still stands, just not with 20 browser tabs.
  - hobs 7y ago
    The important bit is "running our software" - depending on the complexity of said software, 200MB is pretty meh.
    - codegladiator 7y ago
      wait, i had windows xp with firefox and all at 256 mb ram ! which i got later upgraded to 384 mbs because i reused another 128 mb ram chip :)
      - philsnow 7y ago
        In ~2003, I replaced my desktop that had been Intel-based with a Duron 800MHz system, only I didn't have enough budget to get it the RAM it required (new/different slot iirc), so I only had the 128MB it came with (whereas my old machine had 768MB cobbled together from like six dimms). I figured that one hop over 100Mbit Ethernet to remote memory was going to be faster then swapping to spinning rust (remember this was before consumer SSDs, and onions on our belts), so I made a ramdisk on the old machine and mounted it over the network with the nbd (network block device) kernel driver, ran swapon on the nbd and boom, extra "512MB" of RAM. It worked amazingly well, and (knock on wood) none of my roommates ever tripped over the Ethernet cables.
        u6eexrtxjjxjexr 7y ago
        So you're the guy who actually managed to "download more RAM". Congrats! On a more serious note, gonna add that trick to my book - still plenty of rust spinnin' round
        paulmd 7y ago
        Infiniband QDR adapters are amazingly cheap and RDMA-aware software can use DMA to poke directly at memory or devices in the other system.
    - myrandomcomment 7y ago
      Yes. Needed ~150MB per container. It was just simulating end points - ie, TCP connections back to a central system.
u801e 7y ago
What was the remaining 12 MB of RAM used for?
Ao7bei3s 7y ago
He said "The RAM needed for each container was very small" - the RAM is _not_ the limit here. The point is that running many containers is a very different (hard to compare directly) type of load than the main, well optimized use case of running a single large desktop environment. Networking in particular: with thousands of containers, now there are lots more interfaces, routes, conntrack entries, "background" traffic, iptables rules etc. Some problems are algorithmic: for example historically a lot of code has been written with the assumption that the number of network interfaces is small. With >1k interfaces, suddenly O(n) lookups take time. Similarly, iptables rules are run sequentially. etc. Some resources have limits. Exceeding these may impact performance. In his case the load blew up the ARP cache. Nice!
viraptor 7y ago
You're assuming that all the memory was used, even though it's not specified in the post. 512GB/2500 is the upper limit. Anything between 0 and that could be the case.
deleted 7y ago
[deleted]

by ktpsns 7y ago

jjeaff 7y ago

>512GB / 2500 is still 500mb per container Am I missing something? 512gb / 2500 is around 200mb per container.

Mirioron 7y ago
I think he miscalculated. His point still stands, just not with 20 browser tabs.
- hobs 7y ago
  The important bit is "running our software" - depending on the complexity of said software, 200MB is pretty meh.
  - codegladiator 7y ago
    wait, i had windows xp with firefox and all at 256 mb ram ! which i got later upgraded to 384 mbs because i reused another 128 mb ram chip :)
    - philsnow 7y ago
      In ~2003, I replaced my desktop that had been Intel-based with a Duron 800MHz system, only I didn't have enough budget to get it the RAM it required (new/different slot iirc), so I only had the 128MB it came with (whereas my old machine had 768MB cobbled together from like six dimms). I figured that one hop over 100Mbit Ethernet to remote memory was going to be faster then swapping to spinning rust (remember this was before consumer SSDs, and onions on our belts), so I made a ramdisk on the old machine and mounted it over the network with the nbd (network block device) kernel driver, ran swapon on the nbd and boom, extra "512MB" of RAM. It worked amazingly well, and (knock on wood) none of my roommates ever tripped over the Ethernet cables.
      - u6eexrtxjjxjexr 7y ago
        So you're the guy who actually managed to "download more RAM". Congrats! On a more serious note, gonna add that trick to my book - still plenty of rust spinnin' round
        paulmd 7y ago
        Infiniband QDR adapters are amazingly cheap and RDMA-aware software can use DMA to poke directly at memory or devices in the other system.
  - myrandomcomment 7y ago
    Yes. Needed ~150MB per container. It was just simulating end points - ie, TCP connections back to a central system.

u801e 7y ago

What was the remaining 12 MB of RAM used for?

Ao7bei3s 7y ago

He said "The RAM needed for each container was very small" - the RAM is _not_ the limit here. The point is that running many containers is a very different (hard to compare directly) type of load than the main, well optimized use case of running a single large desktop environment. Networking in particular: with thousands of containers, now there are lots more interfaces, routes, conntrack entries, "background" traffic, iptables rules etc. Some problems are algorithmic: for example historically a lot of code has been written with the assumption that the number of network interfaces is small. With >1k interfaces, suddenly O(n) lookups take time. Similarly, iptables rules are run sequentially. etc. Some resources have limits. Exceeding these may impact performance. In his case the load blew up the ARP cache. Nice!

viraptor 7y ago

You're assuming that all the memory was used, even though it's not specified in the post. 512GB/2500 is the upper limit. Anything between 0 and that could be the case.

deleted 7y ago

[deleted]