4 ms·

Huh? What numbers are you looking at? On my laptop (i7-1165G7, DDR4 3200 MHz) lz4 decompression is ~3000 MB/s, compression is ~485 MB/s (on my 3960X desktop it

Huh? What numbers are you looking at? On my laptop (i7-1165G7, DDR4 3200 MHz) lz4 decompression is ~3000 MB/s, compression is ~485 MB/s (on my 3960X desktop it’s ~1.5x that) (numbers from lzbench). Zram by default uses one stream per CPU, so theoretical max is (I think) 8x those for the laptop and, well, a lot more for the Threadripper. Non-Optane SSDs only really have a potential advantage in sequential writing. Max throughput aside, Zram will generally have better latency (and thus likely IOPS as well), and better consistency since most SSDs get their max performance from DRAM caches. In the end, though, quibbling over synthetic numbers doesn’t matter much if you have benchmarked your actual use case. I don’t know what “not beneficial” means (the same? 10x worse?), but part of my original point was that

amarshall 5y ago
(somehow post got cut off, too late to edit) …part of my original point was that Zram will resolve the SSD endurance problems.
- _0w8t 5y ago
  With modern big SSD endurance is no longer the issue. You would need to write at max speed for many month before hitting the limit. I had a laptop with 512GB SSD that I used heavily for 3 years for development work and then for 2 years as a backup machine with light usage. Its write counter reports only 7% of the max usage. So on a new laptop with 2TB SSD after benchmarking things I just disabled zram/zswap. But then again, it was critical to enable hardware encryption on SSD rather than using LUKS on Linux. The latter is so slow [1] that zram is really a must. [1] - https://www.reddit.com/r/Fedora/comments/rzvhyg/default_luks_encryption_settings_on_fedora_can_be/ https://www.reddit.com/r/Fedora/comments/rzvhyg/default_luks...
  - amarshall 5y ago
    Well it all depends on how much writing one does. OP estimates they have 1 year before they use too much of their drive’s endurance. Be aware that on-disk hardware encryption should generally not be trusted. It is not auditable or trivially verifiable. Some years back there were some revelations that some drive firmware encryption was woefully deficient. So much so that whereas Windows previously would treat on-disk encryption as sufficient, Microsoft stopped relying on it entirely.
    - _0w8t 5y ago
      I am aware of this. Plus there are constant power attacks when one disconnects the disk while the system is suspended when the key is unlocked on the disk. But this is a development machine and I figured out that surprisingly non-trivial overhead of LUKS encryption in Linux is not worth it. On the plus side wake up from hibernation is very fast and to mitigate the risk of the above I configured the laptop to hibernate shortly after suspend.
_0w8t 5y ago
You are right, formally lz4 is significantly faster than SSD, see https://www.reddit.com/r/Fedora/comments/mzun99/new_zram_tuning_benchmarks/ https://www.reddit.com/r/Fedora/comments/mzun99/new_zram_tun... . However, I did benchmark using stress-ng my laptop with Samsung 980 PRO SSD and when the stressors had to use swap, using zram or zswap was like 5%-15% slower than the real swap according to bogo ops counters that the tool reported. And the more CPU was taxed during the tests, the slower zram became while CPU utilization has not affected the real swap.

amarshall 5y ago

(somehow post got cut off, too late to edit) …part of my original point was that Zram will resolve the SSD endurance problems.

_0w8t 5y ago
With modern big SSD endurance is no longer the issue. You would need to write at max speed for many month before hitting the limit. I had a laptop with 512GB SSD that I used heavily for 3 years for development work and then for 2 years as a backup machine with light usage. Its write counter reports only 7% of the max usage. So on a new laptop with 2TB SSD after benchmarking things I just disabled zram/zswap. But then again, it was critical to enable hardware encryption on SSD rather than using LUKS on Linux. The latter is so slow [1] that zram is really a must. [1] - https://www.reddit.com/r/Fedora/comments/rzvhyg/default_luks_encryption_settings_on_fedora_can_be/ https://www.reddit.com/r/Fedora/comments/rzvhyg/default_luks...
- amarshall 5y ago
  Well it all depends on how much writing one does. OP estimates they have 1 year before they use too much of their drive’s endurance. Be aware that on-disk hardware encryption should generally not be trusted. It is not auditable or trivially verifiable. Some years back there were some revelations that some drive firmware encryption was woefully deficient. So much so that whereas Windows previously would treat on-disk encryption as sufficient, Microsoft stopped relying on it entirely.
  - _0w8t 5y ago
    I am aware of this. Plus there are constant power attacks when one disconnects the disk while the system is suspended when the key is unlocked on the disk. But this is a development machine and I figured out that surprisingly non-trivial overhead of LUKS encryption in Linux is not worth it. On the plus side wake up from hibernation is very fast and to mitigate the risk of the above I configured the laptop to hibernate shortly after suspend.

_0w8t 5y ago

You are right, formally lz4 is significantly faster than SSD, see https://www.reddit.com/r/Fedora/comments/mzun99/new_zram_tuning_benchmarks/ https://www.reddit.com/r/Fedora/comments/mzun99/new_zram_tun... . However, I did benchmark using stress-ng my laptop with Samsung 980 PRO SSD and when the stressors had to use swap, using zram or zswap was like 5%-15% slower than the real swap according to bogo ops counters that the tool reported. And the more CPU was taxed during the tests, the slower zram became while CPU utilization has not affected the real swap.