linux-kernel - Re: [PATCH 2/9] dma: Convert from tasklet to BH workqueue

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Date: Fri, 29 Mar 2024 22:08:58 +0530
From: Vinod Koul <vkoul@...nel.org>
To: Allen <allen.lkml@...il.com>
Cc: Arnd Bergmann <arnd@...db.de>, Allen Pais <apais@...ux.microsoft.com>,
	linux-kernel@...r.kernel.org, Tejun Heo <tj@...nel.org>,
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Subject: Re: [PATCH 2/9] dma: Convert from tasklet to BH workqueue

On 28-03-24, 13:01, Allen wrote:
> > >> > Since almost every driver associates the tasklet with the
> > >> > dma_chan, we could go one step further and add the
> > >> > work_queue structure directly into struct dma_chan,
> > >> > with the wrapper operating on the dma_chan rather than
> > >> > the work_queue.
> > >>
> > >> I think that is very great idea. having this wrapped in dma_chan would
> > >> be very good way as well
> > >>
> > >> Am not sure if Allen is up for it :-)
> > >
> > >  Thanks Arnd, I know we did speak about this at LPC. I did start
> > > working on using completion. I dropped it as I thought it would
> > > be easier to move to workqueues.
> >
> > It's definitely easier to do the workqueue conversion as a first
> > step, and I agree adding support for the completion right away is
> > probably too much. Moving the work_struct into the dma_chan
> > is probably not too hard though, if you leave your current
> > approach for the cases where the tasklet is part of the
> > dma_dev rather than the dma_chan.
> >
> 
>  Alright, I will work on moving work_struck into the dma_chan and
> leave the dma_dev as is (using bh workqueues) and post a RFC.
> Once reviewed, I could move to the next step.

That might be better from a performance pov but the current design is a
global tasklet and not a per chan one... We would need to carefully
review and test this for sure

-- 
~Vinod