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From dean gaudet <dgaudet-list-new-ht...@arctic.org>
Subject Re: mod_file_cache performance
Date Tue, 03 Jul 2001 01:24:26 GMT
incidentally -- there is an analogue to TCP_CORK on FreeBSD, i'm pretty
sure it's TCP_NOPUSH.  it's unfortunate that the two (almost identical)
concepts developped independantly with different names.

i don't know of any similar feature on other kernels.

-dean

On Mon, 2 Jul 2001, dean gaudet wrote:

> On Mon, 2 Jul 2001, Cliff Woolley wrote:
>
> > On Mon, 2 Jul 2001, dean gaudet wrote:
> >
> > > sendfile() is the best thing to use on linux (and probably everywhere else
> > > that has it).  it doesn't require any virt->phys mappings to be created,
> > > and supports zero-copy.
> >
> > I guess the easy answer is that AP_MIN_BYTES_TO_WRITE ought to be
> > decreased (possibly by a lot).  It's currently set to 8KB.  If it were,
> > say, 1KB, then any file bigger than 1KB would get sendfile'd, even in
> > keepalive requests.  We've been talking about changing it for a while now,
> > and just haven't gotten around to it because no one (that I know of) has
> > done any testing to figure out what a "good" value would be.  How many
> > bytes is "enough" to warrant dumping a packet onto the network?  I don't
> > know for sure, but it's clearly < 8KB.
>
> you don't need to dump a packet on the network... that's what TCP_CORK is
> all about.  see <http://www.kegel.com/c10k.html> and search for TCP_CORK
> to find out more info.
>
> the trick to using TCP_CORK is to understand how the haldduplex /
> safe_read stuff worked in 1.3 -- every time you're in need of blocking on
> read (to get more requests) you want to pop the cork.  you want to put a
> new cork on before you write anything.
>
> also, i seem to be confused -- your earlier description made it sound like
> sendfile() wasn't ever used.
>
> -dean
>
>
>


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