[dpdk-dev] logs about hugepages detection

[Bruce Richardson]

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

/Bruce