RFR (S) 8213587 - Speed up CDS dump time by using resizable hashtables
coleen.phillimore at oracle.com
coleen.phillimore at oracle.com
Fri Nov 16 21:36:19 UTC 2018
Hi Ioi, I really like this new wrapper on the old hashtable to not have
to write the boilerplate code!
http://cr.openjdk.java.net/~iklam/jdk12/8213587-resize-cds-hashtables.v02/src/hotspot/share/utilities/hashtable.hpp.udiff.html
+ MEMFLAGS F = mtInternal,
I think you should require the mt type though and not make it a default
parameter. mtInternal is not very useful to finding memory leaks.
Apart from this (which I don't need to see another version), your change
looks good and nice to get good performance benefits from this.
thanks,
Coleen
On 11/15/18 12:31 AM, Ioi Lam wrote:
> Coleen pointed out to me off-line that the good old (and ugly)
> BasicHashtable already supports resizing. I think that might be a
> better starting point for this RFE:
>
> http://cr.openjdk.java.net/~iklam/jdk12/8213587-resize-cds-hashtables.v02/
>
>
> I wrote a new template class called "KVHashtable" (copying the style
> from ResourceHashtable). That way, you can instantiate different (Key
> -> Value) mappings without writing tons of boilerplate code. The
> performance is similar to my previous version, and the code is much
> cleaner.
>
> I also renamed the RFE title, as well as the subject line of this RFR
> e-mail.
>
> Thanks
>
> - Ioi
>
>
> On 11/14/18 5:14 PM, Jiangli Zhou wrote:
>> Hi Ioi,
>>
>> On 11/14/18 9:09 AM, Ioi Lam wrote:
>>>
>>>
>>> On 11/13/18 4:05 PM, Jiangli Zhou wrote:
>>>> Hi Ioi,
>>>>
>>>> The change looks reasonable to me in general. It would be helpful
>>>> to see the performance difference with the expendable table. Do you
>>>> have any data when large number of classes are loaded (>20000)? How
>>>> much saving does it provide?
>>>>
>>>
>>> Hi Jiangli, thanks for the review. For dumping 30292 classes:
>>>
>>> BEFORE: 93.971 sec
>>> AFTER: 34.761 sec
>>
>> Thanks for the data! That's about 2.6x improvement with large set of
>> classes.
>>
>> Thanks,
>> Jiangli
>>>
>>> Thanks
>>> - Ioi
>>>
>>>> Thanks,
>>>>
>>>> Jiangli
>>>>
>>>>
>>>> On 11/8/18 10:35 PM, Ioi Lam wrote:
>>>>> https://bugs.openjdk.java.net/browse/JDK-8213587
>>>>> http://cr.openjdk.java.net/~iklam/jdk12/8213587-configurable-resource-hash.v01/
>>>>>
>>>>>
>>>>> TL;DR: -- add a subclass to ResourceHashtable to allow the table
>>>>> size to be
>>>>> dynamically specified when the table is constructed.
>>>>>
>>>>>
>>>>> *** C++ template guru alert ***
>>>>>
>>>>>
>>>>> I don't know much about C++ templates, so my attempt on doing this
>>>>> may be
>>>>> ill-advised.
>>>>>
>>>>> I *think* that with my patch, the performance of existing code,
>>>>> which uses
>>>>> a statically-defined SIZE, should not be affected, as the C++
>>>>> compiler
>>>>> should be able to constant-propagate and reduce the new code:
>>>>>
>>>>> ALWAYSINLINE unsigned size() const {
>>>>> if (SIZE != CONFIGURABLE_SIZE) {
>>>>> return SIZE;
>>>>> } else {
>>>>> return _configured_table_size;
>>>>> }
>>>>> }
>>>>>
>>>>> ALWAYSINLINE Node** get_table() const {
>>>>> if (SIZE != CONFIGURABLE_SIZE) {
>>>>> return (Node**)(&_static_table[0]);
>>>>> } else {
>>>>> return _configured_table;
>>>>> }
>>>>> }
>>>>>
>>>>> Node** lookup_node(unsigned hash, K const& key) {
>>>>> unsigned index = hash % size(); <-----
>>>>> Node** table = get_table();
>>>>> Node** ptr = &table[index]; <-----
>>>>>
>>>>> back to the old code:
>>>>>
>>>>> Node** lookup_node(unsigned hash, K const& key) {
>>>>> unsigned index = hash % SIZE; <-----
>>>>> Node** ptr = &_table[index]; <-----
>>>>>
>>>>>
>>>>> If anyone has a better way of doing this, I'd love to hear it!
>>>>>
>>>>> Thanks!
>>>>> - Ioi
>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>
>>
>
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