On Tue, Sep 19, 2000 at 03:24:50PM -0400, Joe Schaefer wrote:
> On linux, the ext2 filesystem is VERY efficient at buffering filesystem
> writes (see http://www.tux.org/lkml/#s9-12). If the post data is small
> ( I don't know what the default size is, but the FILE buffer for the tmpfile
> is adjustable with setvbuf) it's never written to disk. AFAIK, the only
> problem with this arrangement for small posts is the extra file descriptor
> consumed by the apache process.
Yeah, I know it's fairly negligible, but I'm not sure the FILE buffer is
the one that matters here. If I fwrite(), rewind() and then fread()
again, AFAIK libc's stdio still translates this into real kernel
write(), lseek(), read() [strace woudl be the final judge here]. From
there, the kernel can be smart enough to not actually even touch the
disk, but that doesn't work with e.g journaling filesystems which impose
stronger sequential conditions on disk writes, or systems like BSD that
do synchronous metadata updates. And in any case, you're still doing
extra memory copies to and from kernel space.
If it was hard to do it otherwise i'd agree with you, but it sounds so
simple to keep it in a memory buffer when it's under 16k or some similar
limit, that I just think it's much more "obviously right" to do it that
way.
--
Roger Espel Llima, [EMAIL PROTECTED]
http://www.iagora.com/~espel/index.html
