Re: [PATCH 0/2] xfs: fix some new memory allocation failures

Mark Tinguely
2013-09-03T22:38:18Z

On 09/03/13 16:16, Dave Chinner wrote:
> Let's just quote Linus from 2003, shall we:
>
> http://yarchive.net/comp/linux/vmalloc.html
>
> |> I think it'd make more sense to only use vmalloc when it's explicitly
> |> too big for kmalloc - or simply switch on num_online_cpus> 100 or
> |> whatever a sensible cutoff is (ie nobody but you would ever see this ;-))
> |
> | No, please please please don't do these things.
> |
> | vmalloc() is NOT SOMETHING YOU SHOULD EVER USE! It's only valid for when
> | you_need_ a big array, and you don't have any choice. It's slow, and it's
> | a very restricted resource: it's a global resource that is literally
> | restricted to a few tens of megabytes. It should be_very_ carefully used.
> |
> | There are basically no valid new uses of it. There's a few valid legacy
> | users (I think the file descriptor array), and there are some drivers that
> | use it (which is crap, but drivers are drivers), and it's_really_ valid
> | only for modules. Nothing else.
> |
> | Basically: if you think you need more memory than a kmalloc() can give,
> | you need to re-organize your data structures. To either not need a big
> | area, or to be able to allocate it in chunks.
> |
> | Linus
>
> Linus will say exactly the same thing today....

And that is very very sad that is it funny.

--Mark.