Re: patch for x86 treatment of fs and gs in signal handlers

H. Peter Anvin (hpa@transmeta.com)
27 Aug 1998 21:09:47 GMT

Followup to: <3.0.1.16.19980827130136.1157e860@local.hulcote.com>
By author: David Bruce <david@hulcote.com>
In newsgroup: linux.dev.kernel
>
> Hello all
>
> >
> >Once we can to some measurements we might come up with some proposal.
> >Right now I can say that allocating all 8192 LDT entries is overkill
> >for us.
> >
>
> IMHO the LDT allocation is overkill in almost all situations. It should
> be fairly easy to have variable length LDT's allocated in say 512 LDT
> entry chunks.
>
> At the moment it is very easy for LDT's to use up large chunks of your
> physical memory but hold only a few bytes of useful infomation.
>
> Regards
> David Bruce
>

512 descriptors would be a page, which would be a good allocation
size, although for a smaller LDT perhaps a fractional page would make
sense. Note the LDT can be copied/moved if it needs to be
reallocated, so it is "benign" from a memory allocation standpoint.
It could even be swapped out, although at the moment it would require
it to be put in user memory, which wouldn't be a good idea.

-hpa

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