What subsystem!?

[Daniel.]

Vladis,

Thank you so much for your anwer. I had never thought that way, and
make totally sense. Challenge accepted, I'll look for interesting
applications and see how they interact with kernel. Thank you so
much!!!

Best regards!!!

2016-10-25 13:42 GMT-02:00  <Valdis.Kletnieks at vt.edu>:
> On Tue, 25 Oct 2016 10:33:47 -0200, "Daniel." said:
>> I've been studying linux for some time now. I still see my self as an
>> begginer, but that's not a bad thing. I struggling to decide what
>> subsystem to focus right know.
>
> I've said it before, and I'll say it again:
>
> If you have to ask others which part of the kernel you should study,
> maybe you shouldn't be doing kernel work.  It's like a beginning
> author asking other people if they should write a mystery or a western.
> If you're only writing a murder mystery because somebody suggested it,
> it's probably not going to be very good.
>
> Note that for most systems all the *real* magic (and hard work) aren't in
> the kernel, they're in userspace.
>
> Let's look at the Internet of Things as an example.  Yes, networking is
> going to be important - but the kernel just gives userspace (for instance)
> TCP over IPv6.  All the code to actually *do* something with it is out in
> userspace.
>
> Just the other day, a large part of the Internet fell apart because of
> a DDoS attack on some important DNS servers.  The root cause?  Default
> passwords and other userspace security issues on a lot of DVRs and
> security cameras.  A userspace issue.
>
> I'm looking at buying some LED-based light bulbs that can change color on
> command.   Kernel support for the networking?  Get a packet, send a packet.
> All the code that says "during early evening, use a 5K color temperature,
> and slowly roll it back to 3.2K around midnight, but an hour later in the
> kitchen"?  Userspace.
>
> You mention database tuning.  Another case where you *really* need to
> understand what userspace is doing before you can do much in the kernel.
> Linux kernel hacking for tuning our Oracle servers?  Zip.  Zero. None.
> We just create yet another VM with X amount of RAM and Y amount of
> disk on a fiberchannel-connected EMC VNX storage unit.  However, our
> DBAs spend a *lot* of time tweaking Oracle parameters in userspace, and
> my co-worker who administers that storage keeps busy tuning it - but
> he has a nice userspace GUI that handles all the hard work so he can
> concentrate on higher-level issues like proper tiering of a high-activity
> disk.
>
> My current job is building petabyte-scale file systems for HPC clusters -
> and although I end up tweaking kernel parameters a fair amount, there's
> actually not much kernel hacking involved.  What *is* needed is the ability
> to talk to the computational scientists, and find out things like what
> blocksize their software wants to use, whether it's sequential or random
> access, what degree of parallelism is needed, and so on...
>
> You hopefully notice a pattern here... Find an application that *you* think
> is interesting - and first learn the userspace end of it.  You may not need
> to know very much about the kernel at all - and if you *do*, you'll have
> a better idea of which part of the kernel and what you need to know....



-- 
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