Re: [patch 7/8] fdmap v2 - implement sys_socket2

[Davide Libenzi <davidel@xmailserver.org>]

On Thu, 7 Jun 2007, Eric Dumazet wrote:

> Davide, are you sure we want FIFO for non sequential allocations ?
> 
> This tends to use all the fmap slots, and not very cache friendly
> if an app does a lot of [open(),...,close()] things. We already got a 
> perf drop because of RCUification of file freeing (FIFO mode instead 
> of LIFO given by kmalloc()/kfree())
> 
> If the idea behind this FIFO was security (ie not easy for an app to predict 
> next glibc file handle), we/glibc might use yet another FD_SECUREMODE flag, 
> wich ORed with O_NONSEQFD would ask to fdmap_newfd() to take the tail of 
> fmap->slist, not head.

Uli, would it be OK to rely only on base randomization and use a LIFO 
instead? We have base randomization, plus LIFO does not mean strictly 
sequential like legacy allocator, just more compatc and cache friendly.



- Davide


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