Hi Thomas and Harry,
On 3/28/2018 4:22 PM, Van Haaren, Harry wrote:
From: Thomas Monjalon [mailto:tho...@monjalon.net]
Sent: Wednesday, March 28, 2018 8:30 AM
To: Tan, Jianfeng <jianfeng....@intel.com>
Cc: Burakov, Anatoly <anatoly.bura...@intel.com>; dev@dpdk.org; Ananyev,
Konstantin <konstantin.anan...@intel.com>; Van Haaren, Harry
<harry.van.haa...@intel.com>
Subject: Re: [dpdk-dev] [PATCH v6 2/2] eal: add asynchronous request API to
DPDK IPC
28/03/2018 04:08, Tan, Jianfeng:
Hi Thomas ,
From: Thomas Monjalon [mailto:tho...@monjalon.net]
27/03/2018 15:59, Anatoly Burakov:
Under the hood, we create a separate thread to deal with replies to
asynchronous requests, that will just wait to be notified by the
main thread, or woken up on a timer.
I really don't like that a library is creating a thread.
We don't even know where the thread is created (which core).
Can it be a rte_service? or in the interrupt thread?
Agree that we'd better not adding so many threads in a library.
I was considering to merge all the threads into the interrupt thread,
however, we don't have an interrupt thread in freebsd. Further, we don't
implement alarm API in freebsd. That's why I tend to current implementation,
and optimize it later.
I would prefer we improve the current code now instead of polluting more
with more uncontrolled threads.
For rte_service, it may be not a good idea to reply on it as it needs
explicit API calls to setup.
I don't see the issue of the explicit API.
The IPC is a new service.
My concern is that not every DPDK application sets up rte_service, but
IPC will be used for very fundamental functions, like memory allocation.
We could not possibly ask all DPDK applications to add rte_service now.
And also take Harry's comments below into consideration, most likely, we
will move these threads into interrupt thread now by adding
Although I do like to see new services, if we want to enable "core" dpdk functionality
with Services, we need a proper designed solution for that. Service cores is not intended for
"occasional" work - there is no method to block and sleep on a specific service until
work becomes available, so this would imply a busy-polling. Using a service (hence busy polling)
for rte_malloc()-based memory mapping requests is inefficient, and total overkill :)
For this patch I suggest to use some blocking-read capable mechanism.
The problem here is that we add too many threads; blocking-read does not
decrease # of threads.
The above said, in the longer term it would be good to have a design that allows new
file-descriptors to be added to a "dpdk core" thread, which performs occasional
lengthy work if the FD has data available.
Interrupt thread vs rte_service, which is the direction to go? We
actually have some others threads, in vhost and even virtio-user; we can
also avoid those threads if we have a clear direction.
Thanks,
Jianfeng
