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Message-ID: <YGGF4tFogzETutOR@dhcp22.suse.cz>
Date: Mon, 29 Mar 2021 09:46:42 +0200
From: Michal Hocko <mhocko@...e.com>
To: Mike Kravetz <mike.kravetz@...cle.com>
Cc: Roman Gushchin <guro@...com>, Minchan Kim <minchan@...nel.org>,
David Hildenbrand <david@...hat.com>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org, Shakeel Butt <shakeelb@...gle.com>,
Oscar Salvador <osalvador@...e.de>,
Muchun Song <songmuchun@...edance.com>,
David Rientjes <rientjes@...gle.com>,
Miaohe Lin <linmiaohe@...wei.com>,
Peter Zijlstra <peterz@...radead.org>,
Matthew Wilcox <willy@...radead.org>,
HORIGUCHI NAOYA <naoya.horiguchi@....com>,
"Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
Waiman Long <longman@...hat.com>, Peter Xu <peterx@...hat.com>,
Mina Almasry <almasrymina@...gle.com>,
Hillf Danton <hdanton@...a.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: Re: [PATCH 1/8] mm: cma: introduce cma_release_nowait()
On Fri 26-03-21 14:32:01, Mike Kravetz wrote:
[...]
> - Just change the mutex to an irq safe spinlock.
Yes please.
> AFAICT, the potential
> downsides could be:
> - Interrupts disabled during long bitmap scans
How large those bitmaps are in practice?
> - Wasted cpu cycles (spinning) if there is much contention on lock
> Both of these would be more of an issue on small/embedded systems. I
> took a quick look at the callers of cma_alloc/cma_release and nothing
> stood out that could lead to high degrees of contention. However, I
> could have missed something.
If this is really a practical concern then we can try a more complex
solution based on some data.
--
Michal Hocko
SUSE Labs
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