linux-kernel - Re: [PATCH v2 2/2] dmaengine: ioat: Decreasing allocation chunk size 2M -> 512K

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Message-ID: <20200415155359.GT72691@vkoul-mobl>
Date:   Wed, 15 Apr 2020 21:23:59 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     leonid.ravich@...l.com
Cc:     dmaengine@...r.kernel.org, lravich@...il.com,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alexios Zavras <alexios.zavras@...el.com>,
        "Alexander.Barabash@...l.com" <Alexander.Barabash@...l.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Jilayne Lovejoy <opensource@...ayne.com>,
        Logan Gunthorpe <logang@...tatee.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] dmaengine: ioat: Decreasing  allocation chunk
 size 2M -> 512K

On 02-04-20, 19:33, leonid.ravich@...l.com wrote:
> From: Leonid Ravich <Leonid.Ravich@....com>
> 
> current IOAT driver using big (2MB) allocations chunk for its descriptors
> therefore each ioat dma engine need 2 such chunks
> (64k entres in ring  each entry 64B = 4MB)
> requiring 2 * 2M * dmaengine contiguies memory chunk
> might fail due to memory fragmention.

This is quite decent explanation :) pls use upto 72 chars to make it a
better read.

> 
> so we decreasing chunk size and using more chunks.
> 
> Acked-by: Dave Jiang <dave.jiang@...el.com>
> Signed-off-by: Leonid Ravich <Leonid.Ravich@....com>
> ---
>  drivers/dma/ioat/dma.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/dma/ioat/dma.h b/drivers/dma/ioat/dma.h
> index 5216c6b..e6b622e 100644
> --- a/drivers/dma/ioat/dma.h
> +++ b/drivers/dma/ioat/dma.h
> @@ -83,7 +83,7 @@ struct ioatdma_device {
>  
>  #define IOAT_MAX_ORDER 16
>  #define IOAT_MAX_DESCS (1 << IOAT_MAX_ORDER)
> -#define IOAT_CHUNK_SIZE (SZ_2M)
> +#define IOAT_CHUNK_SIZE (SZ_512K)
>  #define IOAT_DESCS_PER_CHUNK (IOAT_CHUNK_SIZE / IOAT_DESC_SZ)
>  
>  struct ioat_descs {
> -- 
> 1.9.3

-- 
~Vinod