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RE: Use of newer locking primitives...
- To: Paul Durrant <xadimgnik@xxxxxxxxx>, "win-pv-devel@xxxxxxxxxxxxxxxxxxxx" <win-pv-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Martin Harvey <martin.harvey@xxxxxxxxxx>
- Date: Tue, 30 Aug 2022 12:00:50 +0000
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- List-id: Developer list for the Windows PV Drivers subproject <win-pv-devel.lists.xenproject.org>
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- Thread-topic: Use of newer locking primitives...
Well now you mention it, I've seen a cpl of amusing cases where
TransmitterRingPollDpc takes 4ms to complete, which leads to Tx jitter. I can
see two potential issues:
- The use of the Tx ring lock as both a lock and a queue. If we undo the "roll
our own" bit on this and use a plain lock and a plain queue, we can then use
the faster sync privitives as tested, debugged, tuned, and tweaked by Microsoft.
- We do a XenBus GntTabRevoke for every single damn fragment individually on
the Tx fast path. There are probably some ways of batching / deferring these so
as to make everything run a bit more smoothly.
MH.
-----Original Message-----
From: win-pv-devel <win-pv-devel-bounces@xxxxxxxxxxxxxxxxxxxx> On Behalf Of
Paul Durrant
Sent: 30 August 2022 12:47
To: win-pv-devel@xxxxxxxxxxxxxxxxxxxx
Subject: Re: Use of newer locking primitives...
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On 30/08/2022 12:35, Martin Harvey wrote:
> Hello folks.
>
> Has anyone taken it upon themselves to try using higher performance
> locking primitives, (i.e. Queued spinlocks) in our drivers? Anyone see
> any issues where we depend on the implementation of locking
> primitives, or could we just do a “drop in” (i.e. search and replace)
> replacement?
>
We have various wrappers around locks in a lot of places so a drop-in
replacement might be doable. I did think about using in-stack queued spinlocks
at one point but the extra argument makes that a pain. Still, probably worth
doing if anyone has the time and motivation.
Paul
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