Re: tux as ftp server question

Could you please compare tux ftp server with the
normal ftp server(such as wu.ftpd) with respective of
data copying(among NIC, kernel space and user space)?
I am sort of confused. Thanks a lot.

sincerely,
li
--- Ingo Molnar <[email protected]> wrote:
> 
> On Tue, 2 Apr 2002, zhang li wrote:
> 
> > Tux reference says tux as FTP server is
> implemented
> > totally in kernel(a C module of 900 lines). So I
> am
> > wondering what's the use of zero-copy in it. It
> seems
> > there is no copy between user-space and
> kernel-space
> > at all, right?
> 
> correct. For sending files, TUX/FTP uses zero-copy,
> just
> like TUX/HTTP does.
> 
> in fact TUX/FTP and TUX/HTTP share much code, it's
> mostly
> the protocol decoding that needs to go into
> proto_ftp.c
> and proto_http.c. Eg. the 'send file' logic is
> shared as
> well.
> 
> > Even if we consider ftp server reads data from a
> file
> > on the disk(when ftp client announce "get"
> command),
> > the data will be put in kernel buffer directly
> after
> > being read, right? So what's the use of zero-copy
> in
> > Tux ftp server?
> 
> if the file is already cached (it's a frequently
> accessed
> file) then TUX will send the file contents to the
> network
> without doing any copying.
> 
> when reading the file contents into RAM from disk,
> then
> TUX [well, the Linux kernel] will DMA it from disk
> into
> RAM straight, without the CPU having to copy the
> data.
> 
> 	Ingo
> 
> 
> 
> _______________________________________________
> tux-list mailing list
> [email protected]
> https://listman.redhat.com/mailman/listinfo/tux-list


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