linux-kernel - Re: [PATCH] Improve scalability of epoll

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Message-ID: <412e6f7f0801081720i61bf2986md68d19db11685218@mail.gmail.com>
Date:	Wed, 9 Jan 2008 09:20:08 +0800
From:	"Changli Gao" <xiaosuo@...il.com>
To:	"Andi Kleen" <andi@...stfloor.org>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Improve scalability of epoll_ctl

On Jan 9, 2008 12:56 AM, Andi Kleen <andi@...stfloor.org> 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);
    else
        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.

-- 
Regards，
Changli Gao(xiaosuo@...il.com)
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