From: David Hildenbrand <david@redhat.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Scott Cheloha <cheloha@linux.vnet.ibm.com>,
linux-kernel@vger.kernel.org,
"Rafael J. Wysocki" <rafael@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
David Hildenbrand <david@redhat.com>,
nathanl@linux.ibm.com, ricklind@linux.vnet.ibm.com,
mhocko@suse.com, Scott Cheloha <cheloha@linux.ibm.com>
Subject: Re: [PATCH v4] drivers/base/memory.c: cache blocks in radix tree to accelerate lookup
Date: Thu, 9 Jan 2020 23:17:09 +0100 [thread overview]
Message-ID: <A7C7E3ED-3A02-43C7-B739-53A7756822D4@redhat.com> (raw)
In-Reply-To: <20200109140004.d5e6dc581b62d6e078dcca4c@linux-foundation.org>
> Am 09.01.2020 um 23:00 schrieb Andrew Morton <akpm@linux-foundation.org>:
>
> On Thu, 9 Jan 2020 15:25:16 -0600 Scott Cheloha <cheloha@linux.vnet.ibm.com> wrote:
>
>> Searching for a particular memory block by id is an O(n) operation
>> because each memory block's underlying device is kept in an unsorted
>> linked list on the subsystem bus.
>>
>> We can cut the lookup cost to O(log n) if we cache the memory blocks in
>> a radix tree. With a radix tree cache in place both memory subsystem
>> initialization and memory hotplug run palpably faster on systems with a
>> large number of memory blocks.
>>
>> ...
>>
>> @@ -56,6 +57,13 @@ static struct bus_type memory_subsys = {
>> .offline = memory_subsys_offline,
>> };
>>
>> +/*
>> + * Memory blocks are cached in a local radix tree to avoid
>> + * a costly linear search for the corresponding device on
>> + * the subsystem bus.
>> + */
>> +static RADIX_TREE(memory_blocks, GFP_KERNEL);
>
> What protects this tree from racy accesses?
I think the device hotplug lock currently (except during boot where no races can happen).
next prev parent reply other threads:[~2020-01-09 22:17 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20191217193238-1-cheloha@linux.vnet.ibm.com>
2020-01-09 21:19 ` [PATCH] drivers/base/memory.c: cache blocks in radix tree to accelerate lookup Scott Cheloha
2020-01-09 21:30 ` Michal Hocko
2020-01-09 21:25 ` [PATCH v4] " Scott Cheloha
2020-01-09 22:00 ` Andrew Morton
2020-01-09 22:17 ` David Hildenbrand [this message]
2020-01-09 22:27 ` Andrew Morton
2020-01-09 22:35 ` David Hildenbrand
2020-01-10 9:32 ` David Hildenbrand
2020-01-10 11:31 ` Michal Hocko
2020-01-15 19:09 ` David Hildenbrand
2020-01-16 15:22 ` Michal Hocko
2020-01-16 15:28 ` David Hildenbrand
2020-01-16 16:17 ` David Hildenbrand
2020-01-17 9:35 ` Michal Hocko
2020-01-20 9:15 ` David Hildenbrand
2020-01-21 12:30 ` Michal Hocko
2020-01-16 17:17 ` Don Dutile
2020-01-21 23:10 ` [PATCH v5] drivers/base/memory.c: cache memory blocks in xarray " Scott Cheloha
2020-01-22 10:43 ` David Hildenbrand
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