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From: Thomas Monjalon <thomas@monjalon.net>
To: Alexander Kozyrev <akozyrev@nvidia.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>,
	Raslan Darawsheh <rasland@nvidia.com>,
	Matan Azrad <matan@nvidia.com>,
	Slava Ovsiienko <viacheslavo@nvidia.com>,
Subject: Re: [dpdk-dev] [PATCH v2] net/mlx5: improve vMPRQ descriptors allocation locality
Date: Fri, 13 Nov 2020 18:58:36 +0100
Message-ID: <2341599.Mj1GBqBveQ@thomas> (raw)
In-Reply-To: <MWHPR12MB1501E9741F8080434986E897DFE90@MWHPR12MB1501.namprd12.prod.outlook.com>

> > There is a performance penalty for the replenish scheme used in vectorized Rx
> > burst for both MPRQ and SPRQ.
> > Mbuf elements are being filled at the end of the mbufs array and being
> > replenished at the beginning. That leads to an increase in cache misses and the
> > performance drop.
> > The more Rx descriptors are used the worse the situation.
> > 
> > Change the allocation scheme for vectorized MPRQ Rx burst:
> > allocate new mbufs only when consumed mbufs are almost depleted (always
> > have one burst gap between allocated and consumed indices). Keeping a small
> > number of mbufs allocated improves cache locality and improves performance
> > a lot.
> > 
> > Unfortunately, this approach cannot be applied to SPRQ Rx burst routine. In
> > MPRQ Rx burst we simply copy packets from external MPRQ buffers or attach
> > these buffers to mbufs.
> > In SPRQ Rx burst we allow the NIC to fill mbufs for us.
> > Hence keeping a small number of allocated mbufs will limit NIC ability to fill as
> > many buffers as possible. This fact offsets the advantage of better cache
> > locality.
> > 
> > Fixes: 0f20acbf5e ("net/mlx5: implement vectorized MPRQ burst")
> > 
> > Signed-off-by: Alexander Kozyrev <akozyrev@nvidia.com>
> Acked-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>

Applied in next-net-mlx, thanks.

      reply	other threads:[~2020-11-13 17:58 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-06  0:04 [dpdk-dev] [PATCH] " Alexander Kozyrev
2020-11-08  4:23 ` [dpdk-dev] [PATCH v2] " Alexander Kozyrev
2020-11-10 16:30   ` Slava Ovsiienko
2020-11-13 17:58     ` Thomas Monjalon [this message]

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