From mboxrd@z Thu Jan  1 00:00:00 1970
From: mjeanson@efficios.com (Michael Jeanson)
Date: Thu, 21 Sep 2017 14:43:19 -0400
Subject: [lttng-dev] [RFC v2] Add kmalloc failover to vmalloc
In-Reply-To: <1705207820.15923.1506019177110.JavaMail.zimbra@efficios.com>
References: <1506018582-22403-1-git-send-email-mjeanson@efficios.com>
 <1705207820.15923.1506019177110.JavaMail.zimbra@efficios.com>
Message-ID: <73494ae7-dd98-4069-6b2c-49fad21698ca@efficios.com>

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.

> 
> Thanks,
> 
> Mathieu