Re: [naviserver-devel] Questions about NS details... (scalability, lib changes)

[Mike <nee...@gm...>]

On 7/12/06, Vlad Seryakov <vl...@cr...> wrote:
> I could be wrong, never used sendfile before.
>
> The code you can check is driver.c, WriterThread, and bufsize parameter
> can be used to define buffer.

Excerpt from sendfile(2) on FreeBSD:

     When using a socket marked for non-blocking I/O, sendfile() may send
     fewer bytes than requested.  In this case, the number of bytes success-
     fully written is returned in *sbytes (if specified), and the error EAGAIN
     is returned.

Overall it looks like it would be very easy to change WriterThread()
to use sendfile() instead of read+memmove+(something).  However the
(something) appears to be NsSockRead() which I am guessing is a bit
more complicated than just an indirect call to write()...  since
probably that code-path supports sending through zlib or over an SSL
socket...

> I was considering using mmap, but somewhere i heard that too many
> mmapped files could be a problem for the server.

mmap is good because it kind of allows zero-copy from usercode..
however it's not useable in my situation directly because of the
32-bit address space restriction - can't mmap 65GB (650MB*100) of
address space...  The solution I've seen others use is to mmap in 16MB
chunks and move the mmaped chunk as the transfer progresses along the
file.