linux-kernel - RE: [PATCH 7/7] irqbypass: Use xarray to track producers and consumers

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Message-ID: <BN9PR11MB5276AF8347DAF3D1C45150728CB62@BN9PR11MB5276.namprd11.prod.outlook.com>
Date: Fri, 11 Apr 2025 00:09:15 +0000
From: "Tian, Kevin" <kevin.tian@...el.com>
To: Sean Christopherson <seanjc@...gle.com>
CC: "Michael S. Tsirkin" <mst@...hat.com>, Jason Wang <jasowang@...hat.com>,
	Paolo Bonzini <pbonzini@...hat.com>, Alex Williamson
	<alex.williamson@...hat.com>, "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"virtualization@...ts.linux.dev" <virtualization@...ts.linux.dev>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Oliver Upton
	<oliver.upton@...ux.dev>, David Matlack <dmatlack@...gle.com>, Like Xu
	<like.xu.linux@...il.com>, Yong He <alexyonghe@...cent.com>
Subject: RE: [PATCH 7/7] irqbypass: Use xarray to track producers and
 consumers

> From: Sean Christopherson <seanjc@...gle.com>
> Sent: Thursday, April 10, 2025 10:52 PM
> 
> On Thu, Apr 10, 2025, Kevin Tian wrote:
> > > From: Sean Christopherson <seanjc@...gle.com>
> > > Sent: Saturday, April 5, 2025 5:15 AM
> > >
> > > Track IRQ bypass produsers and consumers using an xarray to avoid the
> > > O(2n)
> > > insertion time associated with walking a list to check for duplicate
> > > entries, and to search for an partner.
> > >
> > > At low (tens or few hundreds) total producer/consumer counts, using a
> list
> > > is faster due to the need to allocate backing storage for xarray.  But as
> > > count creeps into the thousands, xarray wins easily, and can provide
> > > several orders of magnitude better latency at high counts.  E.g. hundreds
> > > of nanoseconds vs. hundreds of milliseconds.
> >
> > add a link to the original data collected by Like.
> >
> > >
> > > Cc: Oliver Upton <oliver.upton@...ux.dev>
> > > Cc: David Matlack <dmatlack@...gle.com>
> > > Cc: Like Xu <like.xu.linux@...il.com>
> > > Reported-by: Yong He <alexyonghe@...cent.com>
> > > Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217379
> > > Link: https://lore.kernel.org/all/20230801115646.33990-1-
> likexu@...cent.com
> 
> I linked Like's submission here, which has his numbers.  Would it be helpful
> to
> explictly call this out in the meat of the changelog?

No. I just overlooked that line. 😊