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Re: O_DIRECT sockets? (was [RESEND] tuning linux for high network perfo

To: Nivedita Singhvi <niv@xxxxxxxxxx>
Subject: Re: O_DIRECT sockets? (was [RESEND] tuning linux for high network performance?)
From: Roy Sigurd Karlsbakk <roy@xxxxxxxxxxxxx>
Date: Thu, 24 Oct 2002 12:14:59 +0200
Cc: bert hubert <ahu@xxxxxxx>, netdev@xxxxxxxxxxx, Kernel mailing list <linux-kernel@xxxxxxxxxxxxxxx>
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Organization: ProntoTV AS
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> Hmm, I'm still not clear on why you cannot use sendfile()?
> I was not aware of any upper limit to the file size in order
> for sendfile() to be used?  From what little I know, this
> is exactly the kind of situation that sendfile was intended
> to benefit.

I can't use sendfile(). I'm working with files > 4GB, and from man 2 sendfile:

ssize_t sendfile(int out_fd, int in_fd, off_t *offset, size_t count);

int main() {
        ssize_t s1;
        off_t offset;
        size_t count;

        printf("sizeof ssize_t: %d\n", sizeof s1);
        printf("sizeof size_t: %d\n", sizeof count);
        printf("sizeof off_t: %d\n", sizeof offset);
        return 0;

running it

$ ./sendfile_test
sizeof ssize_t: 4
sizeof size_t: 4
sizeof off_t: 4

as far as I'm concerned, this will not allow me to address files past the 4GB 
limit (or was it 2?)


Roy Sigurd Karlsbakk, Datavaktmester
ProntoTV AS -
Tel: +47 9801 3356

Computers are like air conditioners.
They stop working when you open Windows.

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