[dpdk-dev] logs about hugepages detection

[Stephen Hemminger]

On Wed, 15 Sep 2021 15:59:38 +0100
Bruce Richardson <bruce.richardson at intel.com> wrote:

> On Wed, Sep 15, 2021 at 04:39:21PM +0200, Thomas Monjalon wrote:
> > 15/09/2021 16:25, Bruce Richardson:  
> > > On Wed, Sep 15, 2021 at 03:52:35PM +0200, Thomas Monjalon wrote:  
> > > > Hi,
> > > > 
> > > > I would like to discuss some issues in logging of hugepage lookup.
> > > > The issues to be discussed will be enumerated and numbered below.
> > > > I will take an example of an x86 machine with 2M and 1G pages.
> > > > I reserve only 2M pages:
> > > > 
> > > > 	usertools/dpdk-hugepages.py -p 2M -r 80M
> > > > 
> > > > If I start a DPDK application with --log-level info
> > > > the only message I read makes me think something is wrong:
> > > > 
> > > > 	EAL: No available 1048576 kB hugepages reported
> > > > 
> > > > 1/ Log level is too high.
> > > >   
> > > 
> > > Agreed.
> > >   
> > > > If I start with EAL in debug level, I can see which page size is used:
> > > > 
> > > > 	--log-level debug --log-level lib.eal:debug
> > > > 
> > > > 	EAL: No available 1048576 kB hugepages reported
> > > > 	[...]
> > > > 	EAL: Detected memory type: socket_id:0 hugepage_sz:2097152
> > > > 
> > > > 2/ The positive message should be at the same level as the negative one.  
> > > 
> > > A bit uncertain about this, as I think it need not always be the case. I
> > > think the log messages should be assessed independently.  
> > 
> > Not sure what you mean. Which level for which message?
> >   
> 
> I mean the positive and negative log messages. I would assess the positive
> log level independently of what the log level chosen for the negative one,
> rather than saying they should be at the same level.
> 
> > > > 3/ The sizes are sometimes written in bytes, sometimes in kB.
> > > > It should be always the highest unit, including GB.
> > > > 
> > > > When using the --in-memory mode, things are worst:
> > > > 
> > > > 	EAL: No available 1048576 kB hugepages reported
> > > > 	EAL: In-memory mode enabled, hugepages of size 1073741824 bytes will be allocated anonymously
> > > > 	EAL: No free 1048576 kB hugepages reported on node 0
> > > > 	EAL: No available 1048576 kB hugepages reported
> > > > 	[...]
> > > > 	EAL: Detected memory type: socket_id:0 hugepage_sz:1073741824
> > > > 	EAL: Detected memory type: socket_id:0 hugepage_sz:2097152
> > > >   
> > > 
> > > Yes, things should be consistent, having highest units is nice-to-have. If
> > > everything is consistently reported in KB or MB it's probably fine.  
> > 
> > Fine but not nice :)
> > I'm looking to improve the user experience, so "1GB" is definitely easier
> > to read than "1048576 kB", not talking about "1073741824".
> >   
> 
> Yes, agreed. The one small advantage of always just reporting in kB is
> that it is the units used by the kernel in reporting the page sizes:
> 
>   $ ls /sys/kernel/mm/hugepages/
>   hugepages-1048576kB  hugepages-2048kB

Agree the current messages are awkward.
They are too noisy in normal (healthy case); I prefer if every thing is
normal that EAL should print as little as possible, like one line.
And if there is a config problem the current messages don't give the right
diagnostic information for users.