[lfs-support] A speedup with 4.14 and later kernels (againstMeltdown)

[Paul Rogers]

If anyone is still using an older stable kernel on stressed-out
intel hardware, I've just been reading a post which mentions that

"Stressed-out"? Sure I have a couple i7s I *could* use, but these old 6:F:6 Conroe 6700s aren't causing me any impatience. My long-standing RoT is: ignore all performance enhancements that provide less than a 50% boost; don't actively persue any that provide less than 100%; in between only as convenient, free time and the spirit moves you.

Using them for more than compie engines would violate Rule #1: Never try a faster computer than the one you use everyday. It just creates dissatisfaction where there was none before. ;-)

4.14 now *uses* PCID (Processor Context ID, apparently added with
Westmere (previously known as Nehalem-C).

Don't have.

http://archive.is/ma8Iw
And for anybody using i686 on 64-bit-capable CPUs (hi, Paul), you
also get more registers, so it might be worth building a
cross-compiler with gcc-7.3.0 and using that to compile a kernel.

The systems I currently consider usable contain kernels 3.9.11, 4.1.42, & 4.9.75.

Not expecting fixed for 3.9, but would consider upgrading 4.1 to 4.4 except for this: "The Ext3 filesystem has been removed from the Linux core repository. The reason behind this removal is that Ext3 filesystems are fully support by the Ext4 filesystem, and major distros have been already using Ext4 to mount Ext3 filesystems for a long time. With the stabilization of Ext4, maintainers think that the Ext3 codebase is useless duplicated code and should disappear." I don't use Ext4 for backward compatibility on multiboot boxes.

I've just checked Kernel Archives for patches and picked up 4.4.115 & 4.9.81. I searched the Changelogs for "kpti" and "32.b" but found nothing to suggest they have mitigations for 32-bit kernels. Nor 64-bit for that matter.
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Paul Rogers
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[Kuba]

Post by Paul Rogers
Not expecting fixed for 3.9, but would consider upgrading 4.1 to 4.4 except for this: "The Ext3 filesystem has been removed from the Linux core repository. The reason behind this removal is that Ext3 filesystems are fully support by the Ext4 filesystem, and major distros have been already using Ext4 to mount Ext3 filesystems for a long time. With the stabilization of Ext4, maintainers think that the Ext3 codebase is useless duplicated code and should disappear." I don't use Ext4 for backward compatibility on multiboot boxes.

AFAICS, this says "the ext3 driver has been removed because the ext4
driver can mount ext3 filesystems". Using the new version shouldn't
break compatibility with older kernels.

Kuba