linux-kernel - Re: [PATCH] drivers/base/memory.c: memory subsys init: skip search for missing blocks

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Message-ID: <20191102194316.bnglsf5lltc4cztg@rascal.austin.ibm.com>
Date:   Sat, 2 Nov 2019 14:43:16 -0500
From:   Scott Cheloha <cheloha@...ux.vnet.ibm.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     Rick Lindsley <ricklind@...ux.vnet.ibm.com>,
        linux-kernel@...r.kernel.org,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        nathanl@...ux.ibm.com
Subject: Re: [PATCH] drivers/base/memory.c: memory subsys init: skip search
 for missing blocks

On Fri, Nov 01, 2019 at 11:47:49PM +0100, David Hildenbrand wrote:
> 
> > Am 01.11.2019 um 23:32 schrieb Rick Lindsley <ricklind@...ux.vnet.ibm.com>:
> > 
> > On 11/1/19 12:00 PM, David Hildenbrand wrote:
> >> No, I don't really like that. Can we please speed up the lookup via a radix tree as noted in the comment of "find_memory_block()".
> > 
> > I agree with the general sentiment that a redesign is the correct long term action - it has been for some time now - but implementing a new storage and retrieval method and verifying that it introduces no new problems itself is non-trivial.  There's a reason it remains a comment.
> > 
> > I don't see any issues with the patch itself.   Do we really want to forego the short term, low-hanging, low risk fruit in favor of waiting indefinitely for that well-tested long-term solution?
> 
> The low hanging fruit for me is to convert it to a simple VM_BUG_ON(). As I said, this should never really happen with current code.
> 
> Also, I don‘t think adding a radix tree here is rocket science and takes indefinitely ;) feel free to prove me wrong.

To clarify the goal here, "adding a radix tree" means changing
subsys_private's klist_devices member from a klist to a radix
tree or xarray, right?

-Scott