memcached performance on Mac OS 10.4

[Brad Fitzpatrick]

On Thu, 2 Mar 2006, Brad Fitzpatrick wrote:

> If you rebuild libevent with kqueue support, and disable TCP_NOPUSH

_without_ kqueue support, sorry.

> support in memcached (which it tries to auto-detect), then memcached will
> be fast on OS X, but you're limited in your number of concurrent
> connections.  Or rather, it'll eat more CPU as you have more clients
> connected because it has to poll()/select().
>
> The problem, as I understand it, is:
>
>    kqueue is auto-detected, but sucks on OS X.
>
>    NOPUSH is auto-detected, but sucks (on OS X and FreeBSD?) or its
>      semantics diff from TCP_CORK on Linux.  not quite sure.
>
> In any case, a coworker of mine using memcached on OS X (for development,
> not production), had success with the above.
>
> - Brad
>
>
> On Sun, 15 Jan 2006, Peter Bengtson wrote:
>
> > I'm experiencing the previously reported 200 ms latency on each
> > memcached query. As five queries per second is far, far worse than
> > scrapping memcache altogether and running without memory caching, I
> > was wondering if the problems on Mac OS 10.4 have been addressed and/
> > or worked around in any way since Gregory Block wrote the following
> > to this list in March last year:
> >
> > > I had a bug open on Radar regarding memcached causing core dumps when
> > > used in poll(), kevent(), or anything other than select.  I've been
> > > informed by the team that there's a fix in place for Tiger, and that
> > > they've tested under tiger and poll() without seeing the kernel
> > > panics.
> > >
> > > So...
> > >
> > > Until that fix is in place, it's memcached + select() on mac os x, or
> > > watch your kernel go tits up.
> >
> > Of course, libevent since v1.1 has a "workaround", but memcache when
> > using libevent 1.1a and started in the following fashion:
> >
> > 	/usr/local/bin/memcached -k -uroot
> >
> > still reports:
> >
> > 	[warn] kq_init: detected broken kqueue; not using.: Bad file descriptor
> >
> > and then proceeds to respond exactly five times a second.
> >
> > Also, James Robinson wrote, on Aug 30:
> >
> > > stores of payload between 14000 and 195846 bytes all happen on OS X
> > > without delay. Apparently OS X's TCP_NOPUSH is just plain busted, as
> > > seems to be the net wisdom garnered from google.
> >
> > So, I'm wondering what is happening here. Are the Mac OS 10.4
> > implementations of kqueue and TCP_NOPUSH still broken? Are there any
> > patches from Apple or any third-party solutions? And is the slow
> > speed we're seeing the result of select() being inherently slow on
> > Mac OS X? Is there another way of forcing memcached use poll()?
> >
> > 	/ Peter Bengtson
> >
> >
>
>