Re: [patch v2] epoll use a single inode ...

From: H. Peter Anvin
Date: Wed Mar 07 2007 - 02:14:49 EST


Eric Dumazet wrote:
Linus Torvalds a écrit :

On Tue, 6 Mar 2007, Eric Dumazet wrote:
I did a user space program, attached to this mail.

I rewrote the reciprocal_div() for i386 so that one multiply is used.

Ok, this is definitely faster on Core 2 as well, so "numbers talk, bullshit walks". No more objections.

And the numbers were ? :)


(That said, I bet you could do even better for octal and hex numbers, so if you *really* want to speed things up, you should just make a special-case routine for each base (there's just three of them), and you can then also optimize the base-10 thing much better (you can do two digits at a time by dividing by 100, etc)

Well, given that sprintf() is frequently called only for pipe/sockets creation, we probably better :

1) wait a very clever idea to suppress individual dentry per pipe/sockets (no more sprintf() at pipe/socket setup)

2) delay the sprintf() only if needed as you mentioned in a previous mail (when someone wants ls -l /proc/pid/fd/....), since their dentries are not anymore inserted in the global dcache hash, they could stay with a (nul) dname.

Yes, the right thing to do is probably to only generate these strings when someone tries to list them, not on every socket/pipe/epoll creation. One can assign a counter and keep it as a binary value at the start, but create the strings when necessary.

-hpa

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