netdev - Re: [for-next 7/7] IB/mlx5: Implement fragmented completion queue (CQ)

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Message-ID: <223b6be9-4876-d509-492a-dcef92be13de@oracle.com>
Date:   Thu, 22 Feb 2018 16:04:37 -0800
From:   Santosh Shilimkar <santosh.shilimkar@...cle.com>
To:     Saeed Mahameed <saeedm@...lanox.com>,
        "David S. Miller" <davem@...emloft.net>,
        Doug Ledford <dledford@...hat.com>
Cc:     Leon Romanovsky <leonro@...lanox.com>,
        Jason Gunthorpe <jgg@...lanox.com>, netdev@...r.kernel.org,
        linux-rdma@...r.kernel.org, Yonatan Cohen <yonatanc@...lanox.com>,
        Leon Romanovsky <leon@...nel.org>
Subject: Re: [for-next 7/7] IB/mlx5: Implement fragmented completion queue
 (CQ)

Hi Saeed

On 2/21/2018 12:13 PM, Saeed Mahameed wrote:
> From: Yonatan Cohen <yonatanc@...lanox.com>
> 
> The current implementation of create CQ requires contiguous
> memory, such requirement is problematic once the memory is
> fragmented or the system is low in memory, it causes for
> failures in dma_zalloc_coherent().
> 
> This patch implements new scheme of fragmented CQ to overcome
> this issue by introducing new type: 'struct mlx5_frag_buf_ctrl'
> to allocate fragmented buffers, rather than contiguous ones.
> 
> Base the Completion Queues (CQs) on this new fragmented buffer.
> 
> It fixes following crashes:
> kworker/29:0: page allocation failure: order:6, mode:0x80d0
> CPU: 29 PID: 8374 Comm: kworker/29:0 Tainted: G OE 3.10.0
> Workqueue: ib_cm cm_work_handler [ib_cm]
> Call Trace:
> [<>] dump_stack+0x19/0x1b
> [<>] warn_alloc_failed+0x110/0x180
> [<>] __alloc_pages_slowpath+0x6b7/0x725
> [<>] __alloc_pages_nodemask+0x405/0x420
> [<>] dma_generic_alloc_coherent+0x8f/0x140
> [<>] x86_swiotlb_alloc_coherent+0x21/0x50
> [<>] mlx5_dma_zalloc_coherent_node+0xad/0x110 [mlx5_core]
> [<>] ? mlx5_db_alloc_node+0x69/0x1b0 [mlx5_core]
> [<>] mlx5_buf_alloc_node+0x3e/0xa0 [mlx5_core]
> [<>] mlx5_buf_alloc+0x14/0x20 [mlx5_core]
> [<>] create_cq_kernel+0x90/0x1f0 [mlx5_ib]
> [<>] mlx5_ib_create_cq+0x3b0/0x4e0 [mlx5_ib]
> 
> Signed-off-by: Yonatan Cohen <yonatanc@...lanox.com>
> Reviewed-by: Tariq Toukan <tariqt@...lanox.com>
> Signed-off-by: Leon Romanovsky <leon@...nel.org>
> Signed-off-by: Saeed Mahameed <saeedm@...lanox.com>
> ---
Jason mentioned about this patch to me off-list. We were
seeing similar issue with SRQs & QPs. So wondering whether
you have any plans to do similar change for other resouces
too so that they don't rely on higher order page allocation
for icm tables.

Regards,
Santosh