RE: [PATCH v2 1/6] x86/bugs: Add asm helpers for executing VERW

H. Peter Anvin
2023-10-24T20:30:55Z

On October 24, 2023 12:40:02 PM PDT, "Luck, Tony" <tony.luck@intel.com> wrote:
>> Sure it could, but it would mean the kernel is sitting on an average of 6 MB of unusable memory. It would also mean that unloaded modules would create holes in that memory which would have to be managed.
>
>On my Fedora38 desktop:
>
>$ lsmod | awk '{ bytes += $2 } END {print bytes/(1024*1024)}'
>21.0859
>
>Lots more than 6MB memory already essentially pinned by loaded modules.
>
>$ head -3 /proc/meminfo
>MemTotal: 65507344 kB
>MemFree: 56762336 kB
>MemAvailable: 63358552 kB
>
>Pinning 20 or so Mbytes isn't going to make a dent in that free memory.
>
>Managing the holes for unloading/reloading modules adds some complexity ... but shouldn't be awful.
>
>If this code managed at finer granularity than "page", it would save some memory.
>
>$ lsmod | wc -l
>123
>
>All those modules rounding text/data up to 4K boundaries is wasting a bunch of it.
>
>-Tony
>
>
>

Sure, but is it worth the effort?