Hi
> > Hi
> >
> >> void *kvmalloc(size_t size)
> >> {
> >> void *ptr;
> >>
> >> if (size < PAGE_SIZE)
> >> return kmalloc(PAGE_SIZE, GFP_KERNEL);
> >> ptr = alloc_pages_exact(size, GFP_KERNEL | __GFP_NOWARN);
> >
> > low order GFP_KERNEL allocation never fail. then, this doesn't works
> > as you expected.
>
> Hi, I suppose you mean the kmalloc allocation -- so kmalloc should fail
> iff alloc_pages_exact (unless somebody frees a heap of memory indeed)?
I mean, if size of alloc_pages_exact() argument is less than 8 pages,
alloc_pages_exact() never fail. see __alloc_pages_slowpath().
>
> >> if (ptr != NULL)
> >> return ptr;
> >>
> >> return vmalloc(size);
> >
> > On x86, vmalloc area is only 128MB address space. it is very rare
> > resource than physical ram. vmalloc fallback is not good idea.
>
> These functions are a replacement for explicit
> if (!(x = kmalloc()))
> x = vmalloc();
> ...
> if (is_vmalloc(x))
> vfree(x);
> else
> kfree(x);
> in the code (like fdtable does this).
>
> The 128M limit on x86_32 for vmalloc is configurable so if drivers in
> sum need more on some specific hardware, it can be increased on the
> command line (I had to do this on one machine in the past).
Right, but 99% end user don't do this. I don't think this is effective advise.
> Anyway as this is a replacement for explicit tests, it shouldn't change
> the behaviour in any way. Obviously when a user doesn't need virtually
> contiguous space, he shouldn't use this interface at all.
Why can't we make fdtable virtually contiguous free?
Anyway, alloc_fdmem() also don't works as author expected.
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