Re: [PATCH v4 2/2] mempool: optimized debug statistics

[Thomas Monjalon <thomas@monjalon.net>]

30/10/2022 10:09, Morten Brørup:
> > From: Morten Brørup [mailto:mb@smartsharesystems.com]
> > Sent: Friday, 28 October 2022 08.42
> > 
> > When built with debug enabled (RTE_LIBRTE_MEMPOOL_DEBUG defined), the
> > performance of mempools with caches is improved as follows.
> > 
> > Accessing objects in the mempool is likely to increment either the
> > put_bulk and put_objs or the get_success_bulk and get_success_objs
> > debug statistics counters.
> > 
> > By adding an alternative set of these counters to the mempool cache
> > structure, accessing the dedicated debug statistics structure is
> > avoided in
> > the likely cases where these counters are incremented.
> > 
> > The trick here is that the cache line holding the mempool cache
> > structure
> > is accessed anyway, in order to update the "len" field. Updating some
> > debug statistics counters in the same cache line has lower performance
> > cost than accessing the debug statistics counters in the dedicated
> > debug
> > statistics structure, i.e. in another cache line.
> > 
> > Running mempool_perf_autotest on a VMware virtual server shows an avg.
> > increase of 6.4 % in rate_persec for the tests with cache. (Only when
> > built with debug enabled, obviously!)
> > 
> > For the tests without cache, the avg. increase in rate_persec is 0.8 %.
> > I
> > assume this is noise from the test environment.
> > 
> > v4:
> > * Fix spelling and repeated word in commit message, caught by
> > checkpatch.
> > v3:
> > * Try to fix git reference by making part of a series.
> > * Add --in-reply-to v1 when sending email.
> > v2:
> > * Fix spelling and repeated word in commit message, caught by
> > checkpatch.
> > 
> > Signed-off-by: Morten Brørup <mb@smartsharesystems.com>
> 
> I am retracting this second part of the patch series, and reopening the original patch instead. This second part is probably not going to make it to 22.11 anyway.

Indeed, I have decided to take patch 1 only, which is reviewed.

> Instead, I am going to provide another patch series (after 22.11) to split the current RTE_LIBRTE_MEMPOOL_DEBUG define in two: RTE_LIBRTE_MEMPOOL_STATS for statistics, and RTE_LIBRTE_MEMPOOL_DEBUG for debugging. And then this patch can be added to the RTE_LIBRTE_MEMPOOL_STATS.