Re: squid-3.0-PRE3-20031008 w epoll bug?

From: David Nicklay <>
Date: Tue, 14 Oct 2003 11:11:18 -0400


I did some checking on the source code, and can't find anything that
sets read_handler/write_handler except I am compiling a
2.4.21+epoll kernel to test the patch.

David Nicklay wrote:
> Hi,
> The early epoll API was virtual impossible to write for, because it did
> not do an initial poll on new file descriptors you register an interest
> for, so it could not know about notifications that happened before then.
> I just about tore my hair out trying to code around that, and still had
> race conditions to deal with that looked to be impossible to get rid
> of. Coding for edge triggered in squid involves much *pain* and
> *suffering*... :-)
> Having said that Gonzalo's solution seems to be something along the
> lines of what I have looked at in the past. Although, I have to wonder
> if it won't break in some cases, because if I am not mistaken there are
> places in the code that set the read_handler and write_handler settings
> in the squid file descriptor tables without calling CommSetSelect() or
> am I mistaken about that?
> Robert Collins wrote:
>> On Sat, 2003-10-11 at 06:30, Gonzalo Arana wrote:
>>> Hi,
>>> (I'm back to squid-gzip task now).
>>> I come up to this situation:
>>> squid 3.0-PRE3-20031008 with epoll
>>> kernel 2.4.21 patched with
>>> When a client requests a very long object (such as a video), squid uses
>>> 100% of CPU.
>>> It was caused because epoll_wait returned immediately reporting that
>>> connection to client can be written without blocking.
>>> So squid was continously calling to epoll_wait, which in turn returned
>>> immediately.
>> This is something I was about to look into. Thank you.
>> Two things:
>> 1) why the change to COMM_TIMEOUT as the return value? That seems
>> unrelated to the issue.
>> 2) Perhaps we should set the epoll to edge triggered, which IIRC was the
>> default in the early epoll API (and is not now ?)
>> Cheers,
>> Rob

David Nicklay
Location: CNN Center - SE0811A
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Received on Tue Oct 14 2003 - 09:11:20 MDT

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