linux-kernel - Re: [PATCH V5 12/12] net: netvsc: Add Isolation VM support for netvsc driver

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Message-ID: <31da994f-a032-dd40-a90e-bfdaf313d45d@gmail.com>
Date:   Thu, 16 Sep 2021 21:56:11 +0800
From:   Tianyu Lan <ltykernel@...il.com>
To:     Haiyang Zhang <haiyangz@...rosoft.com>,
        Michael Kelley <mikelley@...rosoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
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        Dexuan Cui <decui@...rosoft.com>,
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Cc:     "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
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Subject: Re: [PATCH V5 12/12] net: netvsc: Add Isolation VM support for netvsc
 driver

On 9/16/2021 12:46 AM, Haiyang Zhang wrote:
>>> +				memset(vmap_pages, 0,
>>> +				       sizeof(*vmap_pages) * vmap_page_index);
>>> +				vmap_page_index = 0;
>>> +
>>> +				for (j = 0; j < i; j++)
>>> +					__free_pages(pages[j], alloc_unit);
>>> +
>>> +				kfree(pages);
>>> +				alloc_unit = 1;
>> This is the case where a large enough contiguous physical memory chunk
>> could not be found.  But rather than dropping all the way down to single
>> pages, would it make sense to try something smaller, but not 1?  For
>> example, cut the alloc_unit in half and try again.  But I'm not sure of
>> all the implications.
> I had the same question. But probably gradually decrementing uses too much
> time?
> 

This version is to propose the solution. We may optimize this to try
smaller size until to single page if this is right direction.