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Full response: https://www.spinics.net/lists/dm-crypt/msg07517.html https://www.spinics.net/lists/dm-crypt/msg07517.html From the PoV of the person who respond

by megous 7y ago

Full response: https://www.spinics.net/lists/dm-crypt/msg07517.html https://www.spinics.net/lists/dm-crypt/msg07517.html From the PoV of the person who responded they didn't provide any relevant information that would indicate what platform they run, or what speed they expect, or why they think 800MiB/s seems slow to them. On many platforms this would be a pretty good result. At first look, it looks like they expected the speed of unencrypted storage, because that's what they tried to compare against. So the response seems reasonable at first glance to me. They got the answer to their main question. (which they omitted from their blog article)

gravitas 7y ago
I disagree with your assessment. > If the numbers disturb you, then this is from lack of understanding on your side. This is arrogance on the part of the person replying that hand-waved away their problem "you just don't understand" when in fact, they (Cloudflare) do/did understand. They then went on to prove that it was due to queuing within the kernel, not the hardware as commented by this person in their flippant reply.
- megous 7y ago
  Cloudflare did not understand at the time. Anyway, I'm not questioning that the reply was not very helpful, I just don't see it as unreasonable. I liked the technical parts of the CF writeup overall.
  - marcinzm 7y ago
    >Cloudflare did not understand at the time And neither did the people who responded to them it seems.
  - why_only_15 7y ago
    The next line after that is "You are probably unaware that encryption is a heavy-weight operation". If you're posting to the dm-crypt mailing list about encryption performance, you're probably very aware that encryption is a heavy-weight operation.
tw04 7y ago
I'm not sure why you'd try defending such behavior other than you spent as little time reading the original email as the person who responded in the thread. They clearly state at the bottom their in-memory results - while they don't give EXACT hardware, it's more than enough to determine there is a major bottleneck in the encryption engine. To claim "encryption is heavy" is also a poor response - either the poster has no concept of the overhead of encryption with CPU offload or was just too lazy to put together a helpful response. Either way - no response would've been better than that.
- megous 7y ago
  So who do you get from 4.5GiB/s no encryption vs 850MiB/s with encryption with no other information to understanding whether there's a bottleneck in some unspecified encryption engine (with unknown throughtput and setup latency)?
  - tw04 7y ago
    I dunno, if one of my coworkers had put in the work that OP did, showed me the results, and asked my thoughts: if I didn't have enough information I'd ask for more. If you're telling me you don't have enough information to assume some basics about the setup (I'd look at that and assume it was a modern Intel or AMD CPU just based on the throughput) - then how does he have enough information to dismiss the findings as "then this is from lack of understanding on your side." You can't have your cake and eat it too.
    - megous 7y ago
      Makes sense.
dependenttypes 7y ago
> or what speed they expect "Without LUKS we are getting 450MB/s write, with LUKS we are twice as low at 225MB.s"

by megous 7y ago

gravitas 7y ago

I disagree with your assessment. > If the numbers disturb you, then this is from lack of understanding on your side. This is arrogance on the part of the person replying that hand-waved away their problem "you just don't understand" when in fact, they (Cloudflare) do/did understand. They then went on to prove that it was due to queuing within the kernel, not the hardware as commented by this person in their flippant reply.

megous 7y ago
Cloudflare did not understand at the time. Anyway, I'm not questioning that the reply was not very helpful, I just don't see it as unreasonable. I liked the technical parts of the CF writeup overall.
- marcinzm 7y ago
  >Cloudflare did not understand at the time And neither did the people who responded to them it seems.
- why_only_15 7y ago
  The next line after that is "You are probably unaware that encryption is a heavy-weight operation". If you're posting to the dm-crypt mailing list about encryption performance, you're probably very aware that encryption is a heavy-weight operation.

tw04 7y ago

I'm not sure why you'd try defending such behavior other than you spent as little time reading the original email as the person who responded in the thread. They clearly state at the bottom their in-memory results - while they don't give EXACT hardware, it's more than enough to determine there is a major bottleneck in the encryption engine. To claim "encryption is heavy" is also a poor response - either the poster has no concept of the overhead of encryption with CPU offload or was just too lazy to put together a helpful response. Either way - no response would've been better than that.

megous 7y ago
So who do you get from 4.5GiB/s no encryption vs 850MiB/s with encryption with no other information to understanding whether there's a bottleneck in some unspecified encryption engine (with unknown throughtput and setup latency)?
- tw04 7y ago
  I dunno, if one of my coworkers had put in the work that OP did, showed me the results, and asked my thoughts: if I didn't have enough information I'd ask for more. If you're telling me you don't have enough information to assume some basics about the setup (I'd look at that and assume it was a modern Intel or AMD CPU just based on the throughput) - then how does he have enough information to dismiss the findings as "then this is from lack of understanding on your side." You can't have your cake and eat it too.
  - megous 7y ago
    Makes sense.

dependenttypes 7y ago

> or what speed they expect "Without LUKS we are getting 450MB/s write, with LUKS we are twice as low at 225MB.s"