[dpdk-stable] [dpdk-dev] [PATCH v3] eal: fix create user mem map repeatedly when it exists

[wangyunjian]

> -----Original Message-----
> From: Thomas Monjalon [mailto:thomas at monjalon.net]
> Sent: Monday, November 23, 2020 2:20 AM
> To: anatoly.burakov at intel.com; wangyunjian <wangyunjian at huawei.com>
> Cc: stable at dpdk.org; dev at dpdk.org; david.marchand at redhat.com; Lilijun
> (Jerry) <jerry.lilijun at huawei.com>; xudingke <xudingke at huawei.com>;
> bruce.richardson at intel.com; john.mcnamara at intel.com; asafp at nvidia.com
> Subject: Re: [dpdk-stable] [dpdk-dev] [PATCH v3] eal: fix create user mem map
> repeatedly when it exists
> 
> 15/11/2020 15:23, Thomas Monjalon:
> > 20/10/2020 16:09, Thomas Monjalon:
> > > 16/10/2020 11:28, wangyunjian:
> > > > From: Yunjian Wang <wangyunjian at huawei.com>
> > > >
> > > > Currently, a issue that a container has many devices and the
> > > > application will map the same memory many times. The kernel driver
> > > > returns EEXIST as long as there are overlapping memory areas. As a
> > > > result, we repeatedly create new user mem map entry for the same
> > > > memory segment and this will lead to no more space for other user
> > > > mem maps.
> > > >
> > > > To resolve the issue, add support to remove the same entry in the
> > > > function compact_user_maps().
> > >
> > > Sorry I don't understand the explanations above.
> > > Anatoly, please could you help in rewording?
> >
> > Ping for rewording please.
> 
> What is the conclusion? This fix is not worth the effort?
> 

In my opinion, this issue needs to be fixed. Currently, the 'user_mem_maps->maps[]'
may store many same user mem maps but the maps array is limited, which will lead
to other mem maps cannot be created because of no more space left.

Thanks,
Yunjian