From mboxrd@z Thu Jan  1 00:00:00 1970
From: mathieu.desnoyers@efficios.com (Mathieu Desnoyers)
Date: Thu, 21 Sep 2017 18:52:13 +0000 (UTC)
Subject: [lttng-dev] [RFC v2] Add kmalloc failover to vmalloc
In-Reply-To: <73494ae7-dd98-4069-6b2c-49fad21698ca@efficios.com>
References: <1506018582-22403-1-git-send-email-mjeanson@efficios.com>
 <1705207820.15923.1506019177110.JavaMail.zimbra@efficios.com>
 <73494ae7-dd98-4069-6b2c-49fad21698ca@efficios.com>
Message-ID: <779758199.15975.1506019933645.JavaMail.zimbra@efficios.com>

----- 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