From: Thomas Monjalon <thomas@monjalon.net>
To: Dmitry Kozlyuk <dkozlyuk@nvidia.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>, Matan Azrad <matan@nvidia.com>,
Olivier Matz <olivier.matz@6wind.com>,
Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>,
Slava Ovsiienko <viacheslavo@nvidia.com>,
david.marchand@redhat.com, maxime.coquelin@redhat.com,
bruce.richardson@intel.com, ferruh.yigit@intel.com,
anatoly.burakov@intel.com, jerinj@marvell.com,
honnappa.nagarahalli@arm.com, ajit.khaparde@broadcom.com
Subject: Re: [dpdk-dev] [RFC] mempool: add non-IO flag
Date: Wed, 25 Aug 2021 10:01:33 +0200 [thread overview]
Message-ID: <44052779.eynEIvlN4D@thomas> (raw)
In-Reply-To: <CH0PR12MB509112FADB778AB28AF3771DB9F99@CH0PR12MB5091.namprd12.prod.outlook.com>
+1, I support this idea.
12/08/2021 14:43, Dmitry Kozlyuk:
> We propose to add a mempool flag MEMPOOL_F_NON_IO to mark pools of objects that
> will not be used with device IO and their memory for DMA. This will allow
> saving IOMMU entries by not mapping the memory used by such pools.
>
> Immediate use case is MLX5 PMD. The hardware has its internal IOMMU where PMD
> registers the memory. On the data path, PMD translates VA into a key consumed
> by the device IOMMU. It is impractical for the PMD to register all allocated
> memory because of increased lookup cost both in HW and SW. Most often mbuf
> memory comes from mempools, so if PMD tracked them, it could almost always have
> mbuf memory registered before an mbuf hits the PMD. The new flag would prevent
> the PMD for registering memory that will never need it. Tracking the mempools
> and dealing with them in MLX5 PMD is the next step after the proposed change.
>
> A possible use case is IOMMU management in EAL. Mempool could translate the new
> flag to a hint to the memory manager, which would use it to skip adding IOMMU
> entries in some cases.
>
> It was considered to add MEMPOOL_F_IO with the opposite meaning. It would be
> automatically set for pktmbuf pools; user would be able to set it for other
> pools. However, current assumption is that all DPDK memory is DMA-able,
> it is controversial to have a flag asserting this fact.
next prev parent reply other threads:[~2021-08-25 8:01 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-12 12:43 Dmitry Kozlyuk
2021-08-25 8:01 ` Thomas Monjalon [this message]
2021-08-25 17:28 ` Ajit Khaparde
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