On Jul 17, 2014, at 1:27 PM, D'Alessandro, Luke K <[email protected]> wrote:
> On Jul 17, 2014, at 3:52 PM, Jason Evans <[email protected]> wrote:
>> On Jul 17, 2014, at 11:13 AM, D'Alessandro, Luke K <[email protected]>
>> wrote:
>>> It would be nice to have allocx() dallocx() take a “cache” reference
>>> instead of an arena reference, with the cache configured with arenas to
>>> handle cache misses or something to deal with multithreaded-accesses. Other
>>> than that we really like using the library and as long as our network
>>> memory doesn’t move between cores frequently, this works well.
>>
>> Are you suggesting a system in which each cache is uniquely identified, or
>> one in which every thread potentially has indexable caches [0, 1, 2, ...]?
>> I've given some thought to something similar to the latter: each thread
>> invisibly has a cache layered on top of any arena which is explicitly used
>> for allocation. I'm still in the idea phase on this, so I'm really
>> interested to hear any insights you have.
>
> I haven’t thought it through very hard. :-)
>
> The problem I’m trying to deal with is that we have arenas associated with
> different memories—call them address spaces for now. I want to be able to
> allocate and free from address spaces independently (with the extended
> interface), and have caching work. There may be more than one arena per
> address space, in fact, I’d guess that each thread would have at least one
> arena for each address space. Having to bypass the cache right now is bad for
> us because we start to thrash the allocator with allocx/dallocx from
> different places, so I’d like to be able to cache based on address space.
>
> I think that corresponds to your indexable cache?
It has taken some time, but I think I understand the pain points and use cases
surrounding thread caches well enough now to have a solid plan of action.
Tracking issue:
https://github.com/jemalloc/jemalloc/issues/145
Thanks,
Jason
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