8 ms·

Correct, but 'geofft's criticism of it isn't great, in my opinion. Reading it makes it obvious what it does, and only a fool would disable security mitigations

by kick 7y ago

Correct, but 'geofft's criticism of it isn't great, in my opinion. Reading it makes it obvious what it does, and only a fool would disable security mitigations in a situation where it mattered. The link has significant value in being a quick and easy way to direct people to information, and it seems nonsensical to criticize it for things which don't particularly apply.

saagarjha 7y ago
> Reading it makes it obvious what it does, and only a fool would disable security mitigations in a situation where it mattered. I disagree. Most users do not understand how speculative side channels work or how they might be affected; many people's experience with Meltdown and Spectre is "my games got slower because of some magical speculative stuff that I don't really understand". Making an informed decision on this is hard.
- kick 7y ago
  I may be overestimating them, but I imagine this applies drastically less to your average Linux user who knows how to actually apply this.
  - saagarjha 7y ago
    I think you're overestimating the average Linux user.
    - kick 7y ago
      I could see it.
  - danieldk 7y ago
    The average Linux user will not understand the implications. Heck most don't even know the security trade-offs of X11 (which are relatively simple to discover and understand). Leave the HN bubble and go to an average Linux forum. You would be surprised what kind of advise people give or what people are willing to copy and paste into their terminal ;). This is not meant as a criticism. Most people, including many Linux users, just use their computer as a tool and will just do anything to get it running as they want.
    - kick 7y ago
      I think HN contains most of the least-informed Linux users, actually. Point your eyes to /g/ and you find relatively competent users, if eager to jump on bandwagons. Point your eyes to reddit and take off the bottom 20% of Linux users on it who would never be able to figure out how to enable these, and you get users who are generally-speaking, pretty aware, and arguably better than the average HN user spouting on the same topic.
geofft 7y ago
Do you have an example of a situation where it does not in fact matter, and do you have a benchmark of the speedup?
- kick 7y ago
  Most offline systems, and many systems used only for using trusted code (which obviously bars anything with a web browser, and most internet-connected personal computing devices, among other things). Applications that equate roughly to "Scientific number-crunching" for example are generally systems where security doesn't matter much. There's a case to be made for gaming, and the mitigations if I remember correctly definitely ding performance on quite a few games, but because most computers used for games have significant amounts of sensitive information on them, among other things, I don't think it really holds well. Benchmarks (I really dislike linking to this site, but given it did a bunch of benchmarks, it's not the worst thing, I guess): 'Up to 50% performance loss!' is obviously clickbait, and I disagree with a lot of the wording & conclusions & so on, but there's definitely some workloads where the trade-off makes sense. https://www.phoronix.com/scan.php?page=article&item=linux-420-bisect&num=1 https://www.phoronix.com/scan.php?page=article&item=linux-42... https://www.phoronix.com/scan.php?page=article&item=linux-420-stibp&num=1 https://www.phoronix.com/scan.php?page=article&item=linux-42... Warning about those benchmarks, though: they're of a rather old kernel version, I imagine they tank performance less now. However, given that 5x has been performing way worse to my knowledge than 4x, 4x is probably what most people would be using for these sorts of things. EDIT, added section below: Ah, here we go; how it's effecting modern stuff: https://www.phoronix.com/scan.php?page=article&item=spectre-meltdown-2&num=1 https://www.phoronix.com/scan.php?page=article&item=spectre-... The mitigations ding it a reasonable amount for a substantial amount of workloads, though it's not as intense as it used to be.
  - MelioRatio 7y ago
    Are systems used for "scientific number-crunching" really applicable in this case? While some departments may have those on a separate network, not connected to the internet at large, I have never heard of a system employed for research tasks being completely air gapped. Otherwise, accessing and working on data would be prohibitively harder. Would such a trade-off be worth the potential gains by deactivating mitigations? Also, may I ask why you dislike Phoronix? I personally enjoy their articles and the benchmark suite they have developed seems very well-rounded and transparent. I wouldn't count the statement concerning the ~50% increase in time it takes to complete a certain task on 4.20 as clickbait, considering it was never used in the linked articles title to hock readers and gain clicks. Honestly, I have yet to see a large and popular enough use-case that allows for a both completely air gapped system, whilst also heavily benefiting from disabling mitigation to such an extent, that an admin couldn't just lock up the flags required. If I, as an admin, made the conscious choice of going so far as to disable these patches, I would also want to at least re-read whether this is truly significantly advantageous, rather than copying a line from a website with no context or further information on the current state and impact on performance.
danShumway 7y ago
> only a fool would disable security mitigations in a situation where it mattered. Are we reading the same HN threads on this page? I'm seeing people who I don't consider to be stupid, who obviously have some Linux knowledge, still advocating that user accounts are a waste of time for most desktops. If anyone is smart enough and knows enough about Spectre/Meltdown to understand the risks they're taking, they are also smart enough to search online how to disable the kernel protections. The commands aren't hard to find. If anyone is not smart enough find that information online for themselves, they also don't have enough knowledge to make an informed decision about whether or not it's safe for them to run. In both cases, there is value in forcing users to display a modicum of knowledge about even just the fact that Spectre/Meltdown exist before we give them a command to run that turns off an important security setting. Anyone who knows anything about Spectre/Meltdown already knows that the mitigations affect performance. They should already know what to search for online without the aid of no-context commands being pasted at the top of HN.
- kick 7y ago
  Are we reading the same HN threads on this page? I'm seeing people who I don't consider to be stupid, who obviously have some Linux knowledge, still advocating that user accounts are a waste of time for most desktops. A fool isn't necessarily stupid: plenty of people have knowledge yet terrible judgement. If anyone is smart enough and knows enough about Spectre/Meltdown to understand the risks they're taking, they are also smart enough to search online how to disable the kernel protections. The commands aren't hard to find. If anyone is not smart enough find that information online for themselves, they also don't have enough knowledge to make an informed decision about whether or not it's safe for them to run. In both cases, there is value in forcing users to display a modicum of knowledge about even just the fact that Spectre/Meltdown exist before we give them a command to run that turns off an important security setting. Anyone who knows anything about Spectre/Meltdown already knows that the mitigations affect performance. They should already know what to search for online without the aid of no-context commands being pasted at the top of HN. You're considering it as advice, when really it should be considered more like a doi.
  - 7y ago

by kick 7y ago

saagarjha 7y ago

> Reading it makes it obvious what it does, and only a fool would disable security mitigations in a situation where it mattered. I disagree. Most users do not understand how speculative side channels work or how they might be affected; many people's experience with Meltdown and Spectre is "my games got slower because of some magical speculative stuff that I don't really understand". Making an informed decision on this is hard.

kick 7y ago
I may be overestimating them, but I imagine this applies drastically less to your average Linux user who knows how to actually apply this.
- saagarjha 7y ago
  I think you're overestimating the average Linux user.
  - kick 7y ago
    I could see it.
- danieldk 7y ago
  The average Linux user will not understand the implications. Heck most don't even know the security trade-offs of X11 (which are relatively simple to discover and understand). Leave the HN bubble and go to an average Linux forum. You would be surprised what kind of advise people give or what people are willing to copy and paste into their terminal ;). This is not meant as a criticism. Most people, including many Linux users, just use their computer as a tool and will just do anything to get it running as they want.
  - kick 7y ago
    I think HN contains most of the least-informed Linux users, actually. Point your eyes to /g/ and you find relatively competent users, if eager to jump on bandwagons. Point your eyes to reddit and take off the bottom 20% of Linux users on it who would never be able to figure out how to enable these, and you get users who are generally-speaking, pretty aware, and arguably better than the average HN user spouting on the same topic.

geofft 7y ago

Do you have an example of a situation where it does not in fact matter, and do you have a benchmark of the speedup?

kick 7y ago
Most offline systems, and many systems used only for using trusted code (which obviously bars anything with a web browser, and most internet-connected personal computing devices, among other things). Applications that equate roughly to "Scientific number-crunching" for example are generally systems where security doesn't matter much. There's a case to be made for gaming, and the mitigations if I remember correctly definitely ding performance on quite a few games, but because most computers used for games have significant amounts of sensitive information on them, among other things, I don't think it really holds well. Benchmarks (I really dislike linking to this site, but given it did a bunch of benchmarks, it's not the worst thing, I guess): 'Up to 50% performance loss!' is obviously clickbait, and I disagree with a lot of the wording & conclusions & so on, but there's definitely some workloads where the trade-off makes sense. https://www.phoronix.com/scan.php?page=article&item=linux-420-bisect&num=1 https://www.phoronix.com/scan.php?page=article&item=linux-42... https://www.phoronix.com/scan.php?page=article&item=linux-420-stibp&num=1 https://www.phoronix.com/scan.php?page=article&item=linux-42... Warning about those benchmarks, though: they're of a rather old kernel version, I imagine they tank performance less now. However, given that 5x has been performing way worse to my knowledge than 4x, 4x is probably what most people would be using for these sorts of things. EDIT, added section below: Ah, here we go; how it's effecting modern stuff: https://www.phoronix.com/scan.php?page=article&item=spectre-meltdown-2&num=1 https://www.phoronix.com/scan.php?page=article&item=spectre-... The mitigations ding it a reasonable amount for a substantial amount of workloads, though it's not as intense as it used to be.
- MelioRatio 7y ago
  Are systems used for "scientific number-crunching" really applicable in this case? While some departments may have those on a separate network, not connected to the internet at large, I have never heard of a system employed for research tasks being completely air gapped. Otherwise, accessing and working on data would be prohibitively harder. Would such a trade-off be worth the potential gains by deactivating mitigations? Also, may I ask why you dislike Phoronix? I personally enjoy their articles and the benchmark suite they have developed seems very well-rounded and transparent. I wouldn't count the statement concerning the ~50% increase in time it takes to complete a certain task on 4.20 as clickbait, considering it was never used in the linked articles title to hock readers and gain clicks. Honestly, I have yet to see a large and popular enough use-case that allows for a both completely air gapped system, whilst also heavily benefiting from disabling mitigation to such an extent, that an admin couldn't just lock up the flags required. If I, as an admin, made the conscious choice of going so far as to disable these patches, I would also want to at least re-read whether this is truly significantly advantageous, rather than copying a line from a website with no context or further information on the current state and impact on performance.

danShumway 7y ago

> only a fool would disable security mitigations in a situation where it mattered. Are we reading the same HN threads on this page? I'm seeing people who I don't consider to be stupid, who obviously have some Linux knowledge, still advocating that user accounts are a waste of time for most desktops. If anyone is smart enough and knows enough about Spectre/Meltdown to understand the risks they're taking, they are also smart enough to search online how to disable the kernel protections. The commands aren't hard to find. If anyone is not smart enough find that information online for themselves, they also don't have enough knowledge to make an informed decision about whether or not it's safe for them to run. In both cases, there is value in forcing users to display a modicum of knowledge about even just the fact that Spectre/Meltdown exist before we give them a command to run that turns off an important security setting. Anyone who knows anything about Spectre/Meltdown already knows that the mitigations affect performance. They should already know what to search for online without the aid of no-context commands being pasted at the top of HN.

kick 7y ago
Are we reading the same HN threads on this page? I'm seeing people who I don't consider to be stupid, who obviously have some Linux knowledge, still advocating that user accounts are a waste of time for most desktops. A fool isn't necessarily stupid: plenty of people have knowledge yet terrible judgement. If anyone is smart enough and knows enough about Spectre/Meltdown to understand the risks they're taking, they are also smart enough to search online how to disable the kernel protections. The commands aren't hard to find. If anyone is not smart enough find that information online for themselves, they also don't have enough knowledge to make an informed decision about whether or not it's safe for them to run. In both cases, there is value in forcing users to display a modicum of knowledge about even just the fact that Spectre/Meltdown exist before we give them a command to run that turns off an important security setting. Anyone who knows anything about Spectre/Meltdown already knows that the mitigations affect performance. They should already know what to search for online without the aid of no-context commands being pasted at the top of HN. You're considering it as advice, when really it should be considered more like a doi.
- 7y ago