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Subject: Re: [PATCH rdma-next 1/4] lib/scatterlist: Refactor
 sg_alloc_table_from_pages
To:     Christoph Hellwig <hch@lst.de>, Leon Romanovsky <leon@kernel.org>
CC:     Doug Ledford <dledford@redhat.com>,
        Jason Gunthorpe <jgg@nvidia.com>,
        <linux-kernel@vger.kernel.org>, <linux-rdma@vger.kernel.org>
References: <20200903121853.1145976-1-leon@kernel.org>
 <20200903155434.1153934-1-leon@kernel.org> <20200907072912.GA19875@lst.de>
From:   Maor Gottlieb <maorg@nvidia.com>
Message-ID: <2a4b0211-c7a0-2a82-1335-7ed935b92aa2@nvidia.com>
Date:   Mon, 7 Sep 2020 15:32:31 +0300
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On 9/7/2020 10:29 AM, Christoph Hellwig wrote:
> On Thu, Sep 03, 2020 at 06:54:34PM +0300, Leon Romanovsky wrote:
>> From: Maor Gottlieb <maorg@nvidia.com>
>>
>> Currently, sg_alloc_table_from_pages doesn't support dynamic chaining of
>> SG entries. Therefore it requires from user to allocate all the pages in
>> advance and hold them in a large buffer. Such a buffer consumes a lot of
>> temporary memory in HPC systems which do a very large memory registratio=
n.
>>
>> The next patches introduce API for dynamically allocation from pages and
>> it requires us to do the following:
>>   * Extract the code to alloc_from_pages_common.
>>   * Change the build of the table to iterate on the chunks and not on th=
e
>>     SGEs. It will allow dynamic allocation of more SGEs.
>>
>> Since sg_alloc_table_from_pages allocate exactly the number of chunks,
>> therefore chunks are equal to the number of SG entries.
> Given how few users __sg_alloc_table_from_pages has, what about just
> switching it to your desired calling conventions without another helper?

I tried it now. It didn't save a lot.=C2=A0 Please give me your decision an=
d=20
if needed I will update accordingly.