Re: [dpdk-dev] [EXT] Re: [PATCH v1 2/7] eal/interrupts: implement get set APIs

[Thomas Monjalon <thomas@monjalon.net>]

13/10/2021 19:57, Harman Kalra:
> From: dev <dev-bounces@dpdk.org> On Behalf Of Harman Kalra
> > From: Thomas Monjalon <thomas@monjalon.net>
> > > 04/10/2021 11:57, David Marchand:
> > > > On Mon, Oct 4, 2021 at 10:51 AM Harman Kalra <hkalra@marvell.com>
> > > wrote:
> > > > > > > +struct rte_intr_handle *rte_intr_handle_instance_alloc(int size,
> > > > > > > +                                                      bool
> > > > > > > +from_hugepage) {
> > > > > > > +       struct rte_intr_handle *intr_handle;
> > > > > > > +       int i;
> > > > > > > +
> > > > > > > +       if (from_hugepage)
> > > > > > > +               intr_handle = rte_zmalloc(NULL,
> > > > > > > +                                         size * sizeof(struct rte_intr_handle),
> > > > > > > +                                         0);
> > > > > > > +       else
> > > > > > > +               intr_handle = calloc(1, size * sizeof(struct
> > > > > > > + rte_intr_handle));
> > > > > >
> > > > > > We can call DPDK allocator in all cases.
> > > > > > That would avoid headaches on why multiprocess does not work in
> > > > > > some rarely tested cases.
> > > > > > Wdyt?
> > > > > >
> > > > > > Plus "from_hugepage" is misleading, you could be in --no-huge
> > > > > > mode, rte_zmalloc still works.
> > > > >
> > > > > <HK> In mellanox 5 driver interrupt handle instance is freed in
> > > > > destructor " mlx5_pmd_interrupt_handler_uninstall()" while DPDK
> > > > > memory allocators are already cleaned up in "rte_eal_cleanup".
> > > > > Hence I allocated interrupt instances for such cases from normal heap.
> > > > > There could be other such cases so I think its ok to keep this support.
> > > >
> > > > This is surprising.
> > > > Why would the mlx5 driver wait to release in a destructor?
> > > > It should be done once no interrupt handler is necessary (like when
> > > > stopping all ports), and that would be before rte_eal_cleanup().
> > >
> > > I agree with David.
> > > I prefer a simpler API which always use rte_malloc, and make sure
> > > interrupts are always handled between rte_eal_init and rte_eal_cleanup.
> > > The mlx5 PMD could be reworked to match this requirement.
> > > In any case we should not any memory management in
> > > constructors/destructors.

For info, Dmitry is going to send a fix for mlx5.

> > Hi Thomas, David
> > 
> > There are couple of more dependencies on glibc heap APIs:
> > 1. "rte_eal_alarm_init()" allocates an interrupt instance which is used for
> > timerfd, is called before "rte_eal_memory_init()" which does the memseg
> > init.
> > Not sure what all challenges we may face in moving alarm_init after
> > memory_init as it might break some subsystem inits.
> > Other option could be to allocate interrupt instance for timerfd on first
> > alarm_setup call.

Indeed it is an issue.

[...]

> > There are many other drivers which statically declares the interrupt handles
> > inside their respective private structures and memory for those structure
> > was allocated from heap. For such drivers I allocated interrupt instances also
> > using glibc heap APIs.

Could you use rte_malloc in these drivers?