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From Qian Zhang <zhq527...@gmail.com>
Subject Re: Review Request 60495: Added network ports isolator listen socket utilities.
Date Mon, 04 Sep 2017 07:49:37 GMT


> On Aug. 8, 2017, 11:31 p.m., Qian Zhang wrote:
> > src/slave/containerizer/mesos/isolators/network/ports.cpp
> > Lines 201 (patched)
> > <https://reviews.apache.org/r/60495/diff/7/?file=1785519#file1785519line201>
> >
> >     We should call `os::realpath()` to expand the symbol link.
> 
> James Peach wrote:
>     This (and the use of raw `opendir`) is done for performance reasons. Since we could
be doing this for a lot of sockets, I don't want to take the hit of also doing extra system
calls and memory allocation.
> 
> Qian Zhang wrote:
>     Understand your concern. However `NetworkPortsIsolatorProcess::processSockets()`
is used to process sockets for a single pid, so I do not expect there will be a huge number
files under `/proc/<pid>/fd/`. You can take a look at `os::pids()` (Linux version),
it will call `os::ls()` directly on `/proc` which should have much more entries than `/proc/<pid>/fd/`.
>     
>     And we never call the raw `opendir()`/`readdir()`/`readlinkat()` in Mesos code, instead
we always call the wrapper in `os` namespace which will also simplify your code in this method.
> 
> James Peach wrote:
>     This is doing a `readlink` for every open file on the system. There could easily
be millions of these, so it is worth making an effort to apply the obvious optimizations.
I don't call `os::ls(/proc)` because I'm only interested in processes that are specifically
managed by Mesos. I don't want to know about arbitrary system processes. I see your point
about not using the abstractions, but in this case the abstractions aren't really suitable.

> This is doing a readlink for every open file on the system. There could easily be millions
of these

I think it is doing a readlink for every open file on *a single process* rather than the system,
so for a single process, is it possible for it to have millions of open files? I think usually
the open file limit per process should be thousands (like 4096).


- Qian


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On Aug. 15, 2017, 7:40 a.m., James Peach wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://reviews.apache.org/r/60495/
> -----------------------------------------------------------
> 
> (Updated Aug. 15, 2017, 7:40 a.m.)
> 
> 
> Review request for mesos, Qian Zhang and Jiang Yan Xu.
> 
> 
> Bugs: MESOS-7675
>     https://issues.apache.org/jira/browse/MESOS-7675
> 
> 
> Repository: mesos
> 
> 
> Description
> -------
> 
> Implemented network ports isolator socket utilities to find the
> inode numbers of all the listening sockets, and the inodes of the
> open sockets for a process. Together, these utilities can tell us
> which sockets a process is listening on.
> 
> 
> Diffs
> -----
> 
>   src/slave/containerizer/mesos/isolators/network/ports.hpp PRE-CREATION 
>   src/slave/containerizer/mesos/isolators/network/ports.cpp PRE-CREATION 
> 
> 
> Diff: https://reviews.apache.org/r/60495/diff/13/
> 
> 
> Testing
> -------
> 
> make check (Fedora 26)
> 
> 
> Thanks,
> 
> James Peach
> 
>


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