[lttng-dev] [RFC v2] Add kmalloc failover to vmalloc

[mathieu.desnoyers@efficios.com (Mathieu Desnoyers)]

----- On Sep 21, 2017, at 2:43 PM, Michael Jeanson mjeanson at efficios.com wrote:

> On 2017-09-21 14:39, Mathieu Desnoyers wrote:
>> ----- On Sep 21, 2017, at 2:29 PM, Michael Jeanson mjeanson at efficios.com wrote:
>> 
>>> This patch is based on the kvmalloc helpers introduced in kernel 4.12.
>>>
>>> It will gracefully failover memory allocations of more than one page to
>>> vmalloc for systems under high memory pressure or fragmentation.
>>>
>>> I only used it in lttng-events.c as a POC, most allocations fit into a
>>> single page so I'm not sure how useful this actually is.
>>>
>>> Thoughts?
>> 
>> Just update the changelog to specify why we need this for struct lttng_session
>> (~32kB), and you can submit it for good with a "Fix: " tag.
> 
> I'm not sure it should be a fix, for this to be of any use all the other
> allocations bigger than PAGE_SIZE should also use it. Otherwise, the
> session allocation will succeed but the next sizeable allocation will
> still fail.

What other allocations larger than PAGE_SIZE using kmalloc did you spot ?

Thanks,

Mathieu


> 
>> 
>> Thanks,
>> 
> > Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com