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From: Aurelien Aptel <aaptel@nvidia.com>
To: David Laight <David.Laight@ACULAB.COM>,
	"linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"sagi@grimberg.me" <sagi@grimberg.me>, "hch@lst.de" <hch@lst.de>,
	"kbusch@kernel.org" <kbusch@kernel.org>,
	"axboe@fb.com" <axboe@fb.com>,
	"chaitanyak@nvidia.com" <chaitanyak@nvidia.com>,
	"davem@davemloft.net" <davem@davemloft.net>,
	"kuba@kernel.org" <kuba@kernel.org>
Cc: "aurelien.aptel@gmail.com" <aurelien.aptel@gmail.com>,
	"smalin@nvidia.com" <smalin@nvidia.com>,
	"malin1024@gmail.com" <malin1024@gmail.com>,
	"ogerlitz@nvidia.com" <ogerlitz@nvidia.com>,
	"yorayz@nvidia.com" <yorayz@nvidia.com>,
	"borisp@nvidia.com" <borisp@nvidia.com>,
	"galshalom@nvidia.com" <galshalom@nvidia.com>,
	"mgurtovoy@nvidia.com" <mgurtovoy@nvidia.com>,
	"viro@zeniv.linux.org.uk" <viro@zeniv.linux.org.uk>
Subject: RE: [PATCH v24 03/20] iov_iter: skip copy if src == dst for direct data placement
Date: Thu, 18 Apr 2024 11:22:42 +0300	[thread overview]
Message-ID: <253h6fzaxm5.fsf@nvidia.com> (raw)
In-Reply-To: <a779982fc59f4b9b94d619d0bb111738@AcuMS.aculab.com>

Hi David,

David Laight <David.Laight@ACULAB.COM> writes:
> How must does this conditional cost for the normal case
> when it is true?
> I suspect it is mispredicted 50% of the time.
> So, while it may speed up your test, the overall system
> impact will be negative.

We have done some measures to evaluate the cost of the additional test
and we don't see any noticeable impact on performances.

If this is still a concern, we can add compilation-time check on
CONFIG_ULP_DDP i.e. ifdef or IS_ENABLED() (which gets optimized out).

Thanks


  reply	other threads:[~2024-04-18  8:23 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-04-04 12:36 [PATCH v24 00/20] nvme-tcp receive offloads Aurelien Aptel
2024-04-04 12:36 ` [PATCH v24 01/20] net: Introduce direct data placement tcp offload Aurelien Aptel
2024-04-21 11:47   ` Sagi Grimberg
2024-04-26  7:21     ` Aurelien Aptel
2024-04-28  8:15       ` Sagi Grimberg
2024-04-29 11:35         ` Aurelien Aptel
2024-04-30 11:54           ` Sagi Grimberg
2024-05-02  7:04             ` Aurelien Aptel
2024-05-03  7:31               ` Sagi Grimberg
2024-05-06 12:28                 ` Aurelien Aptel
2024-04-04 12:36 ` [PATCH v24 02/20] netlink: add new family to manage ULP_DDP enablement and stats Aurelien Aptel
2024-04-04 12:37 ` [PATCH v24 03/20] iov_iter: skip copy if src == dst for direct data placement Aurelien Aptel
2024-04-15 14:28   ` Max Gurtovoy
2024-04-16 20:30   ` David Laight
2024-04-18  8:22     ` Aurelien Aptel [this message]
2024-04-04 12:37 ` [PATCH v24 04/20] net/tls,core: export get_netdev_for_sock Aurelien Aptel
2024-04-21 11:45   ` Sagi Grimberg
2024-04-04 12:37 ` [PATCH v24 05/20] nvme-tcp: Add DDP offload control path Aurelien Aptel
2024-04-07 22:08   ` Sagi Grimberg
2024-04-10  6:31     ` Aurelien Aptel
2024-04-04 12:37 ` [PATCH v24 06/20] nvme-tcp: Add DDP data-path Aurelien Aptel
2024-04-07 22:08   ` Sagi Grimberg
2024-04-10  6:31     ` Aurelien Aptel
2024-04-04 12:37 ` [PATCH v24 07/20] nvme-tcp: RX DDGST offload Aurelien Aptel
2024-04-04 12:37 ` [PATCH v24 08/20] nvme-tcp: Deal with netdevice DOWN events Aurelien Aptel
2024-04-04 12:37 ` [PATCH v24 09/20] Documentation: add ULP DDP offload documentation Aurelien Aptel
2024-04-09  8:49   ` Bagas Sanjaya
2024-04-04 12:37 ` [PATCH v24 10/20] net/mlx5e: Rename from tls to transport static params Aurelien Aptel
2024-04-04 12:37 ` [PATCH v24 11/20] net/mlx5e: Refactor ico sq polling to get budget Aurelien Aptel
2024-04-04 12:37 ` [PATCH v24 12/20] net/mlx5: Add NVMEoTCP caps, HW bits, 128B CQE and enumerations Aurelien Aptel
2024-04-04 12:37 ` [PATCH v24 13/20] net/mlx5e: NVMEoTCP, offload initialization Aurelien Aptel
2024-04-04 12:37 ` [PATCH v24 14/20] net/mlx5e: TCP flow steering for nvme-tcp acceleration Aurelien Aptel
2024-04-04 12:37 ` [PATCH v24 15/20] net/mlx5e: NVMEoTCP, use KLM UMRs for buffer registration Aurelien Aptel
2024-04-04 12:37 ` [PATCH v24 16/20] net/mlx5e: NVMEoTCP, queue init/teardown Aurelien Aptel
2024-04-04 12:37 ` [PATCH v24 17/20] net/mlx5e: NVMEoTCP, ddp setup and resync Aurelien Aptel
2024-04-04 12:37 ` [PATCH v24 18/20] net/mlx5e: NVMEoTCP, async ddp invalidation Aurelien Aptel
2024-04-04 12:37 ` [PATCH v24 19/20] net/mlx5e: NVMEoTCP, data-path for DDP+DDGST offload Aurelien Aptel
2024-04-04 12:37 ` [PATCH v24 20/20] net/mlx5e: NVMEoTCP, statistics Aurelien Aptel
2024-04-06  5:45 ` [PATCH v24 00/20] nvme-tcp receive offloads Jakub Kicinski
2024-04-07 22:21   ` Sagi Grimberg
2024-04-09 22:35     ` Chaitanya Kulkarni
2024-04-09 22:59       ` Jakub Kicinski
2024-04-18  8:29         ` Chaitanya Kulkarni
2024-04-18 15:28           ` Jakub Kicinski

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