Slow cache misses using binary protocol

[dtakken]

Hello,

I was experimenting with php-memcached binary mode, and I noticed that my PHP script became very, very slow when I enabled the binary protocol. The server load went to near zero, indicating that something is just sitting and waiting while doing nothing at all. I managed to isolate the problem into a simple test case (see below). It turned out that an attempt to get() a non-existing key requires about 30 ms to complete. As soon as the binary protocol is turned off, response times are back to normal.

I'm on Ubuntu Server 12.04 (64-bit). The PHP script and the memcached server run on two seperate servers. Package versions are:

php5-memcached-1.0.2-2
libmemcached 0.44-1.1build1
memcached 1.4.13-0ubuntu2

I also tried to compile the latest memcached PECL from source, which did not make any difference.

A PHP script which reproduces the problem is shown below. Can anyone else reproduce this?

setOption(Memcached::OPT_BINARY_PROTOCOL, True); $Cache -> addServers(array ( array ("172.16.0.20","11211","0") )); $Counter = 0; $Start = time(); print("Getting 1000 Keys..."); while ($Counter < 1000) { $Cache -> get("test"); $Counter++; } $End = time(); $Speed = 1000.0 / ($End - $Start); print("Done, $Speed per second.\n");

[quentin389]

Try enabling Memcached::OPT_TCP_NODELAY - that completely fixed all empty key gets on my server.

[dtakken]

Thanks a lot, that fixed the problem.