6 ms·
So is there no way to disable the performance crippling fix? If you ran an air gapped or highly controlled environment wouldn’t you want th option of disabling
by dexwiz 9y ago
So is there no way to disable the performance crippling fix? If you ran an air gapped or highly controlled environment wouldn’t you want th option of disabling this to keep performance? How many Giga Terra or Exo FLops will be lost to this fix in super computers? Or is the way to disable it just not merge this patch into your custom kernel code?
- revelation 9y agoThis isn't the fix with the 5% quoted performance loss (that one clears all of TLB on every syscall), I don't think this is as costly. But it's certainly not free and it's certainly not clean. I'm disappointed Intel didn't bother to test the performance impact of this and report it in the patchset. Benchmarks are ordinarily expected with something like this (very hot paths they are changing), and they did have 6 months..
- userbinator 9y agoThis is worse, far worse --- it basically disables prediction for indirect jumps and calls, plus adds another few extra clock cycles to each one of those for the "retoline" instruction sequence.
- PhantomGremlin 9y agoI'm disappointed Intel didn't bother to test the performance impact of this and report it in the patchset. You should be disappointed that they didn't report it. But I'd be willing to bet every last dollar of my net worth that Intel has done very extensive performance testing. I'd venture that the results are far too embarrassing to report.
- barkingcat 9y agoYup this for sure. They probably ran the performance test bench thousands of times, and only then released it with the PR department fully briefed about how bad it was going to be.
- zik 9y agoIt can be controlled by a boot option in linux.
- userbinator 9y agoNot this one, which basically penalises every indirect call by preventing them from being speculatively executed.
- wilun 9y agoI don't see why the text could not be fixed at boot time. It has been done before.
- jtc331 9y agoBecause this actually changes how every indirect call is compiled.
- wilun 9y agoSo what? IIRC we used to have (and maybe still have) a feature that patched out spinlocks in binary code when it detects it is run on monoprocessor systems. You "just" have to identify all the call sites, and patch the code there during the boot process.
- Decabytes 9y agoCorrect me if I'm wrong, but I don't think super computers are updating there kernels at all.
- ams6110 9y agoThey do, but not often. Maybe once a year or so.
- striking 9y agoNew software is written with newer kernels in mind. To continue running newer software, you will need to update your kernels. Additionally: you might update infrequently when it comes to feature releases, but you'll definitely need security patches.