| 1 |
On 6/16/19 7:02 PM, Wols Lists wrote: |
| 2 |
> So you didn't read what I wrote ... Par for the course :-( |
| 3 |
|
| 4 |
I did. I still hear people say it today. It's not old as in past tense. |
| 5 |
|
| 6 |
> The basic Unix mechanism needs twice ram. |
| 7 |
|
| 8 |
I disagree. |
| 9 |
|
| 10 |
> It's inherent in the design of the thing. Whether linux no longer |
| 11 |
> uses the Unix mechanism, or it's had the hell optimised out of it I |
| 12 |
> don't know. |
| 13 |
> |
| 14 |
> Either way, machines today get by on precious little swap - that's |
| 15 |
> fine. |
| 16 |
> |
| 17 |
> Historic note - the early linux 2.4 vanilla kernels enforced the twice |
| 18 |
> ram rule - a lot of people who didn't read the release notes got nasty |
| 19 |
> shocks when their machines locked up the moment they touched swap ... |
| 20 |
|
| 21 |
I disagree because I ran 2.0, 2.2, 2.4, and 2.6 kernels without swap |
| 22 |
being twice the ram or greater. Swap did get used. They did not crash |
| 23 |
when accessing swap. |
| 24 |
|
| 25 |
> And okay my machine only has 16GB of ram (and 64GB of swap - 32GB |
| 26 |
> each across two disks), but I'm pretty sure that if I followed your |
| 27 |
> guidelines, an emerge would crash my system as the tmpfs ran out of |
| 28 |
> space ... |
| 29 |
|
| 30 |
I doubt it. |
| 31 |
|
| 32 |
I've routinely done emerges on machines with < 16 GB of memory and 2 GB |
| 33 |
of swap. Including llvm, clang, gcc, rust, Firefox and Thunderbird. |
| 34 |
|
| 35 |
I routinely do an emerge -DuNe @world on a VPS with 1 GB of memory and 1 |
| 36 |
GB of swap. It works just fine. If I want to speed things up I enlarge |
| 37 |
the VPS to 2 GB of memory and 1 GB of swap. Granted, it doesn't try to |
| 38 |
compile things like Firefox and Thunderbird, thus Rust. |
| 39 |
|
| 40 |
> And those people who wrote your guidelines? |
| 41 |
|
| 42 |
I just looked again, and Red Hat has lowered their recommendation from |
| 43 |
what I remember from a few years ago. |
| 44 |
|
| 45 |
Link - Table 15.1. Recommended System Swap Space |
| 46 |
- |
| 47 |
https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/storage_administration_guide/ch-swapspace#tb-recommended-system-swap-space |
| 48 |
|
| 49 |
RAM ≤ 2 GB = swap should be 2 times the amount of RAM |
| 50 |
2 < RAM ≤ 8 GB = swap should be equal to the amount of RAM |
| 51 |
8 < RAM ≤ 64 GB = swap should be at least 4 GB |
| 52 |
64 < RAM = swap should be at least 4 GB |
| 53 |
|
| 54 |
> Are they the same clueless people who believe the twice ram rule is |
| 55 |
> pure fiction? |
| 56 |
|
| 57 |
I don't consider Red Hat's official statement to be "clueless". |
| 58 |
|
| 59 |
Seeing as how their rules include "twice the RAM" in the first |
| 60 |
condition, I don't think they thought it was pure fiction. |
| 61 |
|
| 62 |
> (As I said, it is *historical* *fact*). |
| 63 |
|
| 64 |
I question the validity of that statement. |
| 65 |
|
| 66 |
> And why should I believe people who tell me the rule no longer |
| 67 |
> applies, if they can't tell me WHY it no longer applies? I'd love |
| 68 |
> to be enlightened - why can't anybody do that? |
| 69 |
|
| 70 |
I'm not saying you should believe people. |
| 71 |
|
| 72 |
My opinion is that the 2 x RAM no longer applies because systems don't |
| 73 |
utilize swap space. As such it's a waste of disk space to dedicate 2 x |
| 74 |
RAM to swap. |
| 75 |
|
| 76 |
Look at the output of free. Or better, run sysstat / SAR and watch swap |
| 77 |
usage. How much does your system use? How much disk space to you want |
| 78 |
to dedicate to something that's likely hardly being touched. |
| 79 |
|
| 80 |
Do what you want. |
| 81 |
|
| 82 |
But be prepared to put the shoe on the other foot and explain why you |
| 83 |
think that you should have 2 x RAM on each disk. |
Archives