Re: [patch] epoll reduced (to 1) number of passes over the ready set ...

On Wed, 28 Feb 2007, Eric Dumazet wrote:

On Tuesday 27 February 2007 17:03, Davide Libenzi wrote:
On Tue, 27 Feb 2007, Eric Dumazet wrote:
On Tuesday 27 February 2007 03:32, Davide Libenzi wrote:
Epoll is doing multiple passes over the ready set at the moment,
because of the constraints over the f_op->poll() call. Looking at the
code again, I noticed that we already hold the epoll semaphore in read,
and this (together with other locking conditions that hold while doing
an epoll_wait()) can lead to a smarter way to "ship" events to
userspace (in a single pass). I added more (even) more comments to the
code to explain the conditions why certain operations are safe.
This is a stress application that can be used to test the new code. It
spwans multiple thread and call epoll_wait() and epoll_ctl() from many
threads. Stress tested on my dual Opteron 254 w/out any problems.

Davide,

This is really cool, because the size of epitem would fit now in 128
bytes instead of 192 (on x86_64 platforms). So we also reduce memory
usage.

Yeah, I forgot to mention that I removed the txlink member.

I am pretty sure you can also remove revents member from epitem.

It would greatly benefit to 32bits platforms, because resulting size would be
64 bytes instead of 68 (so a 50 % reduction because of 64 bytes alignment)

Yes indee. That does not need to exist anymore, once the de-coupled loop
is gone. Thx, I'll make a new patch later today.


- Davide


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