candump: epoll_wait() instead of select() runs faster and better keeps packet order

[IDC-Dragon]

Using epoll_wait() instead of select() gives higher performance for listening on multiple interfaces. Additionally, the read order has a higher chance to resemble the true temporal order. select() gives implicit priority to the lower index socket.

[IDC-Dragon]

select() is a horrible beast of the past. We should use epoll today, it is in the kernel longer than CAN support.
If you like the patch, I may change the other tools, too.

[hartkopp]

Hi Jörg,
many thanks for your effort!
I'll take a look at it and do some testing (which I assume you already did).
Btw. the commit message is completely broken. There is no Signed-off-by: tag and the commit message has a separated subject line and a desrciption with a line break at ~70 chars.
I applied your patch to my repo and fixed the commit message there:
hartkopp@4ca36df

[marckleinebudde]

Thanks for the patch, some nitpicks inline.

[marckleinebudde]

@IDC-Dragon, can you squash and force push the change, so that there is only one commit

[IDC-Dragon]

Not sure if I did squash+push correct, don't see an effect on the pull request. I did:
git rebase -i origin/master~2 master
git push origin +master

[marckleinebudde]

squahing means, make one commit from multiple ones. Your master branch still contains two commits.

[IDC-Dragon]

I missed the squash in the rebase. Now it is one commit.

[ehartko]

Can you please change the commit message as suggested here:
#264 (comment)
git --amend is your friend ;-)

[marckleinebudde]

some nitpicks left

[IDC-Dragon]

force-pushed again, it seems my editor messed the indentation in one place

[marckleinebudde]

You have some idention problem still: feel free to squash my commit:

https://github.com/marckleinebudde/can-utils/commits/for-IDC-Dragon

[marckleinebudde]

Now please rewrap you commit message to < 80 chars per line. Then we're good to go.

[IDC-Dragon]

Now please rewrap you commit message to < 80 chars per line. Then we're good to go.

Done, I may shall say.

[marckleinebudde]

It fails on android...

/home/travis/build/marckleinebudde/can-utils/candump.c:392:13: warning: implicit declaration of function 'epoll_create1' is invalid in C99 [-Wimplicit-function-declaration]
1086        fd_epoll = epoll_create1(0);

[marckleinebudde]

Let's try with epoll_create() instead.
https://github.com/marckleinebudde/can-utils/tree/epoll
https://travis-ci.org/github/marckleinebudde/can-utils/builds/747858023

[marckleinebudde]

epoll_create() works

@IDC-Dragon can you update the patch, then I'll merge it.