sonewconn: pcb 0xfffff801efdd1000: Listen queue overflow: 31 already in queue awaiting acceptance

Charles Swiger cswiger at
Tue Mar 17 00:01:52 UTC 2015

On Mar 16, 2015, at 4:48 PM, David Benfell <benfell at> wrote:
> On Mon, Mar 16, 2015 at 03:38:51PM -0700, Charles Swiger wrote:
>> They aren't directly related.  You generally need to increase apc.shm_size
>> suitable for however many PHP processes you're running-- generally via mod_php
>> in Apache or fastcgi for nginx and the like.
> I *am* running a bunch of php-fpm processes. Is there a formula for
> calculating this?

There's an apc.php script which will look at your APC stats.

>> The listen queue overflow means that your system is failing to process
>> incoming requests fast enough to keep up.  The bottleneck could be
>> on a resource like CPU or memory, or serialization against a database
>> table, or something else.  (You'll want to identify the bottleneck.)
> Interesting. htop says I've got plenty of memory and CPU--it's a new
> server and I went big. That would seem to suggest mysql may not be
> performing well, which is a very strong possibility. Until relatively
> recently, I was trying to run on a VPS and then a rather small hosted
> server; I don't think I've revisited the mysql configuration since.
> Thank you very much. All this helps.

mysql is a likely candidate, particularly if it was an old setup and has
not been tuned for the workload.  For example, MyISAM is adequate for
read-mostly stuff, but table-level locking tends to become a real problem
if you have more than a single admin instance doing writes.


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