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SubjectRe: [PATCH] Improve scalability of epoll_ctl
On Jan 9, 2008 12:56 AM, Andi Kleen <> wrote:
> Are you sure it's faster? vmalloc/vfree can be quite slow because
> they have to change the MMU state of the kernel and take global
> locks.
I don't think so. In fact, the memory of fdtable is allocated by
vmalloc when its size is bigger than PAGE_SIZE:

static inline void * alloc_fdmem(unsigned int size)
if (size <= PAGE_SIZE)
return kmalloc(size, GFP_KERNEL);
return vmalloc(size);

> The other problem is that on 32bit systems vmalloc space is somewhat
> limited -- you might have added an unintended scaling limit.

As I have talked above, I am sure open(), socket() and etc. will first
encounter it.

Changli Gao(

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