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From: Slava Ovsiienko <viacheslavo@nvidia.com>
To: Alexander Kozyrev <akozyrev@nvidia.com>, "dev@dpdk.org" <dev@dpdk.org>
Cc: Raslan Darawsheh <rasland@nvidia.com>, Matan Azrad <matan@nvidia.com>
Subject: Re: [dpdk-dev] [PATCH v2] net/mlx5: improve vMPRQ descriptors allocation locality
Date: Tue, 10 Nov 2020 16:30:10 +0000
Message-ID: <MWHPR12MB1501E9741F8080434986E897DFE90@MWHPR12MB1501.namprd12.prod.outlook.com> (raw)
In-Reply-To: <20201108042357.28542-1-akozyrev@nvidia.com>

> -----Original Message-----
> From: Alexander Kozyrev <akozyrev@nvidia.com>
> Sent: Sunday, November 8, 2020 6:24
> To: dev@dpdk.org
> Cc: Raslan Darawsheh <rasland@nvidia.com>; Matan Azrad
> <matan@nvidia.com>; Slava Ovsiienko <viacheslavo@nvidia.com>
> Subject: [PATCH v2] net/mlx5: improve vMPRQ descriptors allocation locality
> 
> 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>


  reply	other threads:[~2020-11-10 16:30 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 [this message]
2020-11-13 17:58     ` Thomas Monjalon

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