Intel CPU Bug Performance Loss Reports Are Premature

Update, 1/4/18, 8:00am PT: We now have statements from several semiconductor vendors and news on the exploits. Read more at: Understanding The Meltdown And Spectre Exploits: Intel, AMD, ARM and Nvidia.

Update, 1/3/18, 1:00pm PT: Intel has responded to the reports and disputes claims of a bug. 

According to recent reports, Intel and ARM processors suffer a serious hardware-level vulnerability that the vendors cannot patch via a microcode update. Addressing the vulnerability requires a significant retooling of operating systems, in particular Windows, Linux, and macOS, which reportedly causes up to a 30% reduction in performance in some workloads.

However, that number is likely overblown for the majority of applications. The overall impact of the performance regression and the specific programs impacted are poorly defined. As with many pre-release security patches, the details surrounding the bug are under NDA for now, but we expect an official update from Intel soon. Both Microsoft and Linux already have patches in the pipeline. AMD's exposure to the bug remains undefined, with some reports indicating the company's processors are immune and others stating that some models are impacted.

What We Know About The Vulnerability

The vulnerability reportedly allows programs to access protected areas of the kernel memory, but the exact nature of the bug is yet unclear. The potential exploits, and what they could do, are also undefined. We do know the fix requires separating the user and kernel memory pages with kernel page-table isolation (KPTI). Some ingrained hardware features on Intel processors, such as PCID (Process-Context Identifier), can lessen the overhead of separating the two spaces, but these features aren't present on older Intel processors.

The Performance Impact

We also know that Microsoft has already deployed patches in the fast ring Windows Insider builds. Those patches rolled out in November. Notably, there haven't been any reports of massive performance degradation from participants of the Insider Ring. Linux patches are already available. For now, the patches are confined to the operating system. It is possible that application patches could also help lessen the impact.

A note of caution: The bug will have an impact on some programs, but the chance of a widespread 30% reduction in performance is slim. Phoronix conducted testing on the patched Linux 4.15-rc6 kernel with an Intel Core i7-6800K and an i7-8700K. It tested applications that are confined to the user space, which are typically indicative of what you would see on a desktop system, and found that these applications "should see minimal change (if any) in performance." That means you will likely see little to no performance impact on your next desktop session, be it gaming or otherwise.

Phoronix did record significant performance regressions with the new kernel during select workloads, particularly synthetic I/O benchmarks. The site conducted these tests with SSDs that tend to offer varying performance based on the amount of past user activity, and the article doesn't indicate if the storage devices were correctly preconditioned. Phoronix noted the new kernel has other changes beyond the bug patch that could also impact performance, so for now, it is hard to ascertain the direct impact of the patch on these workloads.

The performance impact is more pronounced in PostgreSQL, which is an open source object-relational database system. PostgreSQL has issued a warning about performance regression that includes benchmarks showing a 17-23% reduction in performance with the new patch. Redis also appears to suffer a performance loss, but to a lesser extent.

So Much FUD

The vulnerability appears to be most dangerous to data center workloads and virtualization. However, it is irrational to assume that the overwhelming majority of data centers will see a 30% reduction in performance. Losing even 15% of the computational horsepower from a data center would be a major blow, and that compute would have to be replaced almost immediately. The patch has been in development for several months, so if Intel and the major data center operators were expecting massive performance reductions, there would have been an incredible spike in data center equipment purchases.

Also, we would have likely already seen signs of a pending financial disaster for Intel if there was a serious threat of hardware replacements to a wide swath of the data center. Intel's customers would likely be able to pursue litigation for widespread losses that are directly the fault of Intel. It's also reasonable to assume that the company would be required to replace faulty processors. For instance, Intel disclosed during its Q4 2016 earnings call that it had encountered a higher-than-expected failure rate for some of its processors, so it established a financial reserve to deal with the costs of replacements. We reported on Intel's statements, and later the fund was connected to failures in Intel's Atom C2000 processors. In no recent financial commentary has Intel disclosed the establishment of any new funds, so it appears the company doesn't foresee significant hardware replacements any time soon.

Intel CEO Brian Krzanich also recently sold $11 million in stock, which some have proclaimed is a sign that he's unloading his shares before a pending disaster. However, Krzanich sold the stock under a 10b-51 plan, which is a pre-planned sale of stocks intended to prevent insider trading. The nature of Krzanich's transactions makes it unlikely that the trades are a precursor of a major monetary loss for the company.

Currently, there are no major shifts in Intel's stock that would indicate a mass sell-off by investors. There are conflicting reports about the impact to AMD processors, and AMD's shares are currently up 5%. However, such an increase is a fairly common occurrence for the sometimes-volatile AMD stock, so the bump may be incidental; in any case, it's not out of the ordinary. Update, 1/3/18, 11:00am PT: AMD's shares are now up 9% and Intel is down 6%.

For now, we await more detail on the nature of the bug and its impact. We expect an update to emerge in a future Patch Tuesday update, but Microsoft has not listed an official release date.

The bug is locked behind a wall of NDAs at this point, which is frustrating. However, the silence is necessary to prevent a wave of exploits. We expect, and have seen already, the normal level of hyperventilation that comes with such news, but it's best to wait for more information. We have followed up with Intel for more information and will update as necessary.

Paul Alcorn
Managing Editor: News and Emerging Tech

Paul Alcorn is the Managing Editor: News and Emerging Tech for Tom's Hardware US. He also writes news and reviews on CPUs, storage, and enterprise hardware.

  • jpe1701
    Hopefully it doesn't degrade performance too much. We need tech moving forward not back.
  • bloodroses
    20553854 said:
    Hopefully it doesn't degrade performance too much. We need tech moving forward not back.

    If it does though, it gives an excuse to sell new hardware. Tech is unfortunately a double edged sword like that. :(
  • oscurokeyz
    Can someone explain why if it's a hardware CPU issue that they can not patch the firmware to fix it? Doesn't the firmware basically have the driver that talks to OS?
  • eathdemon
    early benchmarks seem to show no gaming impact, but I do wounder about emulation. ether way I pity benchmarkers who now will have to redo a ton of benchmarks when this patch hits.
  • ssdpro
    At least these things are disclosed and patched. They could just let that stuff ride.
  • danwat1234
    If it does turn out to give a big performance impact, I will not be installing it. Just keep away from malicious software! Supposedly impacts Intel CPUs 10 years old, which would include Core 2 Duos! No thanks I don't need an excuse for my nine-year-old Asus G50VT Core 2 Duo extreme laptop to slow down. Especially because older CPS or probably have a higher percentage of impact than newer ones because of lack of certain instruction sets.

    Finally, consider the impact of power consumption and increased e-junk because of this and most will let the patch install! Horrible!

    Will security Suites such as Norton Internet Security, Kaspersky, e t c, do the job also? Doesn't look like it.
  • steve23063
    "Currently, there are no major shifts in Intel's stock that would indicate a mass sell-off by investors. "

    Intel's stock today is experiencing the worst sell off since Oct 2016
  • lumineZ
    If it turns out to impact the performance by lets say 25%.

    Intel will just spin this around when they release the new CPU line with this:

    " Our new CPU is minimum 25% faster than the old one!!! Now run and buy!!!" :D
  • InvalidError
    20553909 said:
    Can someone explain why if it's a hardware CPU issue that they can not patch the firmware to fix it? Doesn't the firmware basically have the driver that talks to OS?
    The CPU microcode regulates only parts of how instructions are executed and can only be used to fix or work around bugs that are within what the microcode can act upon. If a flaw concerns parts of the CPU's operation that are hard-wired, then the microcode can only address part of the bug at most and a software trap needs to be used to restore the CPU to the state it should be in after the problematic instruction(s).

    Not all CPU bugs can be fixed with microcode and many of them aren't severe enough for Intel to do anything about, which is why Intel's errata contains about a hundred active bugs for Kaby Lake (and just about any other CPU Intel ever made, I just happened to land on Kaby's "Specifications Update" first) with no fixes planned.
  • PaulAlcorn
    20554235 said:
    "Currently, there are no major shifts in Intel's stock that would indicate a mass sell-off by investors. "

    Intel's stock today is experiencing the worst sell off since Oct 2016

    "Currently" was at the time of writing. Intel was at -1.4%, now it is down 5%, which still isn't as low as it was two weeks ago. We do see the slump, and now AMD is up much more. We will cover the developments after the picture settles a bit.