linux-kernel - Re: [PATCH 1/3] radix-tree: propagate all tags in idr tree

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Date:   Wed, 15 Jun 2022 21:33:22 +0800
From:   Ian Kent <ikent@...hat.com>
To:     Christoph Hellwig <hch@...radead.org>,
        Brian Foster <bfoster@...hat.com>
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        onestero@...hat.com
Subject: Re: [PATCH 1/3] radix-tree: propagate all tags in idr tree


On 15/6/22 19:12, Christoph Hellwig wrote:
> On Tue, Jun 14, 2022 at 02:09:47PM -0400, Brian Foster wrote:
>> The IDR tree has hardcoded tag propagation logic to handle the
>> internal IDR_FREE tag and ignore all others. Fix up the hardcoded
>> logic to support additional tags.
>>
>> This is specifically to support a new internal IDR_TGID radix tree
>> tag used to improve search efficiency of pids with associated
>> PIDTYPE_TGID tasks within a pid namespace.
> Wouldn't it make sense to switch over to an xarray here rather
> then adding new features to the radix tree?
>
Might be a dumb question but ...


How would the, essentially sparse, pid type PIDTYPE_TGID pids

traversal get benefits from an xarray?


 From what I have seen the searching isn't the real problem, it's the

traversal (that, at the moment, does a search 'and' a traversal over

a lot of pids to get a relatively small number of them).

Ian