Re: [PATCH 3/12 2.4] e1000 - use vmalloc for data structures not shared with h/w

Re: [PATCH 3/12 2.4] e1000 - use vmalloc for data structures not shared with h/w

[Herbert Xu]

Christoph Hellwig <hch@infradead.org> wrote:
> On Thu, Jul 29, 2004 at 11:17:08AM -0700, Venkatesan, Ganesh wrote:
>> Vmalloc space is less scarce than kmalloc space. Am I right? This patch
>> trades kmalloc space for vmalloc space.
> 
> No, it's not.  vmalloc needs virtual space that's rather limited (e.g. 64MB
> on PAE x86) in addition to physical memory.  Unless you do really big
> allocations stay away from vmalloc.

How big is really big? 64K? 256K? 1M?

Thanks,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: [PATCH 3/12 2.4] e1000 - use vmalloc for data structures not shared with h/w

[Christoph Hellwig]

On Sat, Jul 31, 2004 at 05:38:11PM +1000, Herbert Xu wrote:
> > No, it's not.  vmalloc needs virtual space that's rather limited (e.g. 64MB
> > on PAE x86) in addition to physical memory.  Unless you do really big
> > allocations stay away from vmalloc.
> 
> How big is really big? 64K? 256K? 1M?

Well, the VM deals with big-order (aka bigger than page size) allocations
rather bad, so for allocation during any I/O I'd stick to allocation smaller
than that (and certainly no vmalloc!), for init-time allocations order 1 is
fine, maybe even order 2 or three.