RE: [PATCH] mempool: dump includes list of memory chunks

["Morten Brørup" <mb@smartsharesystems.com>]

> From: Konstantin Ananyev [mailto:konstantin.ananyev@huawei.com]
> Sent: Monday, 10 June 2024 15.45
> 
> > Added information about the memory chunks holding the objects in the
> > mempool when dumping the status of the mempool to a file.
> >
> > Signed-off-by: Morten Brørup <mb@smartsharesystems.com>
> > ---
> >  lib/mempool/rte_mempool.c | 10 ++++++++++
> >  1 file changed, 10 insertions(+)
> >
> > diff --git a/lib/mempool/rte_mempool.c b/lib/mempool/rte_mempool.c
> > index 12390a2c81..e9a8a5b411 100644
> > --- a/lib/mempool/rte_mempool.c
> > +++ b/lib/mempool/rte_mempool.c
> > @@ -1230,6 +1230,7 @@ rte_mempool_dump(FILE *f, struct rte_mempool *mp)
> >  #endif
> >  	struct rte_mempool_memhdr *memhdr;
> >  	struct rte_mempool_ops *ops;
> > +	unsigned int n;
> >  	unsigned common_count;
> >  	unsigned cache_count;
> >  	size_t mem_len = 0;
> > @@ -1264,6 +1265,15 @@ rte_mempool_dump(FILE *f, struct rte_mempool *mp)
> >  			(long double)mem_len / mp->size);
> >  	}
> >
> > +	fprintf(f, "  mem_list:\n");
> > +	n = 0;
> > +	STAILQ_FOREACH(memhdr, &mp->mem_list, next) {
> > +		fprintf(f, "    addr[%u]=%p\n", n, memhdr->addr);
> > +		fprintf(f, "    iova[%u]=0x%" PRIx64 "\n", n, memhdr->iova);
> > +		fprintf(f, "    len[%u]=%zu\n", n, memhdr->len);
> > +		n++;
> > +	}
> > +
> >  	cache_count = rte_mempool_dump_cache(f, mp);
> >  	common_count = rte_mempool_ops_get_count(mp);
> >  	if ((cache_count + common_count) > mp->size)
> > --
> 
> Just as a thought: do we want to print something (N/A?) when mp->mem_list is
> empty?

Good idea, Konstantin.

Your feedback made me check what other dump functions print when the list is empty, and I saw that the mbuf library's dump function prints segments with multiple fields on the same line [1], as previously suggested by Stephen (and rejected by me, because I thought it was breaking conventions).

[1]: https://elixir.bootlin.com/dpdk/v24.03/source/lib/mbuf/rte_mbuf.c#L694

Admitting that Stephen was on the right track with his suggestion, and I was wrong to reject it, we could omit the "mem_list:" header and print the list like this instead:

STAILQ_FOREACH(memhdr, &mp->mem_list, next)
	fprintf(f, "    memory chunk at %p, addr=%p, iova=0x%" PRIx64 ", len=%zu\n",
			memhdr, memhdr->addr, memhdr->iova, memhdr->len);

The patch will be just these three lines of code, and nothing will be printed if the list is empty.

What do you think?

> 
> Acked-by: Konstantin Ananyev <konstantin.ananyev@huawei.com>
> 
> 
> > 2.17.1