From: Konstantin Ananyev <konstantin.ananyev@huawei.com>
To: Dariusz Sosnowski <dsosnowski@nvidia.com>,
Stephen Hemminger <stephen@networkplumber.org>
Cc: "NBU-Contact-Thomas Monjalon (EXTERNAL)" <thomas@monjalon.net>,
"Ferruh Yigit" <ferruh.yigit@amd.com>,
Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>,
Ori Kam <orika@nvidia.com>, "dev@dpdk.org" <dev@dpdk.org>
Subject: RE: [RFC] ethdev: fast path async flow API
Date: Thu, 4 Jan 2024 08:47:02 +0000 [thread overview]
Message-ID: <4efb00a7f6f3406ab819424ac7a25542@huawei.com> (raw)
In-Reply-To: <IA1PR12MB8311C2B7D70FA8E1157A94E1A460A@IA1PR12MB8311.namprd12.prod.outlook.com>
> > This is a blocker, showstopper for me.
> +1
>
> > Have you considered having something like
> > rte_flow_create_bulk()
> >
> > or better yet a Linux iouring style API?
> >
> > A ring style API would allow for better mixed operations across the board and
> > get rid of the I-cache overhead which is the root cause of the needing inline.
> Existing async flow API is somewhat close to the io_uring interface.
> The difference being that queue is not directly exposed to the application.
> Application interacts with the queue using rte_flow_async_* APIs (e.g., places operations in the queue, pushes them to the HW).
> Such design has some benefits over a flow API which exposes the queue to the user:
> - Easier to use - Applications do not manage the queue directly, they do it through exposed APIs.
> - Consistent with other DPDK APIs - In other libraries, queues are manipulated through API, not directly by an application.
> - Lower memory usage - only HW primitives are needed (e.g., HW queue on PMD side), no need to allocate separate application
> queues.
>
> Bulking of flow operations is a tricky subject.
> Compared to packet processing, where it is desired to keep the manipulation of raw packet data to the minimum (e.g., only packet
> headers are accessed),
> during flow rule creation all items and actions must be processed by PMD to create a flow rule.
> The amount of memory consumed by items and actions themselves during this process might be nonnegligible.
> If flow rule operations were bulked, the size of working set of memory would increase, which could have negative consequences on
> the cache behavior.
> So, it might be the case that by utilizing bulking the I-cache overhead is removed, but the D-cache overhead is added.
Is rte_flow struct really that big?
We do bulk processing for mbufs, crypto_ops, etc., and usually bulk processing improves performance not degrades it.
Of course bulk size has to be somewhat reasonable.
> On the other hand, creating flow rule operations (or enqueuing flow rule operations) one by one enables applications to reuse the
> same memory for different flow rules.
>
> In summary, in my opinion extending the async flow API with bulking capabilities or exposing the queue directly to the application is
> not desirable.
> This proposal aims to reduce the I-cache overhead in async flow API by reusing the existing design pattern in DPDK - fast path
> functions are inlined to the application code and they call cached PMD callbacks.
>
> Best regards,
> Dariusz Sosnowski
next prev parent reply other threads:[~2024-01-04 8:47 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-27 10:57 Dariusz Sosnowski
2023-12-27 17:39 ` Stephen Hemminger
2023-12-27 17:41 ` Stephen Hemminger
2023-12-28 13:53 ` Dariusz Sosnowski
2023-12-28 14:10 ` Ivan Malov
2024-01-03 18:01 ` Dariusz Sosnowski
2024-01-03 18:29 ` Ivan Malov
2024-01-04 13:13 ` Dariusz Sosnowski
2023-12-28 17:16 ` Stephen Hemminger
2024-01-03 19:14 ` Dariusz Sosnowski
2024-01-04 1:07 ` Stephen Hemminger
2024-01-23 11:37 ` Dariusz Sosnowski
2024-01-29 13:38 ` Dariusz Sosnowski
2024-01-29 17:36 ` Ferruh Yigit
2024-01-30 12:06 ` Dariusz Sosnowski
2024-01-30 12:17 ` Ferruh Yigit
2024-01-30 16:08 ` Dariusz Sosnowski
2024-01-04 8:47 ` Konstantin Ananyev [this message]
2024-01-04 16:08 ` Dariusz Sosnowski
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