From: Kefeng Wang <wangkefeng.wang@huawei.com>
To: Vlastimil Babka <vbabka@suse.cz>, Chris Down <chris@chrisdown.name>
Cc: <linux-mm@kvack.org>, Andrew Morton <akpm@linux-foundation.org>,
"Muchun Song" <songmuchun@bytedance.com>,
Michal Hocko <mhocko@kernel.org>,
"Matthew Wilcox" <willy@infradead.org>,
Chunxin Zang <zangchunxin@bytedance.com>
Subject: Re: [PATCH] mm, vmscan: guarantee drop_slab_node() termination
Date: Thu, 19 Aug 2021 17:38:29 +0800 [thread overview]
Message-ID: <76a1baa8-8970-84fb-c4af-f071dfbc88bc@huawei.com> (raw)
In-Reply-To: <47437115-1a84-c1d1-d91e-1d23cf7f4a5d@suse.cz>
On 2021/8/19 15:01, Vlastimil Babka wrote:
> On 8/19/21 4:55 AM, Kefeng Wang wrote:
>> On 2021/8/19 5:48, Chris Down wrote:
>>> Vlastimil Babka writes:
>>>
>>> I think this is a good idea, thanks for bringing it up :-)
>>>
>>> I'm not sure about the bitshift idea, though. It certainly makes sure
>>> that even large, continuous periods of reclaim eventually terminates,
>>> but I find it hard to reason about -- for example, if there's a lot of
>>> parallel activity, that might result in 10 constantly reintroduced
>>> pages, or 1000 pages, and it's not immediately obvious that we should
>>> treat those differently.
>>>
>>> What about using MAX_RECLAIM_RETRIES? There's already precedent for
>>> using it in non-OOM scenarios, like mem_cgroup_handle_over_high.
> It's an option, but then (together with fixed threshold) it ignores how
> large the 'freed' value is, as long it's above threshold? Although the
> end result will probably not be much different.
>
>> Yes, we meet this issue too, and we add a max loop limit in
>> drop_slab_node() in our kernel, which also could be reconfigured by
>> sysctl ;)
> Sysctl sounds like an overkill. How do you tune the limit? Any
> experience with what scenarios need what limit?
This is no clear limit, we do some test, then choose a big limit which
is tolerated
by our user, and the user could change it dynamically by sysctl interface.
The dynamically growing threshold is great, I am very agree with this patch.
Like Chris said, the option is that we could also add a max limit then
let's the
user to make a decision according their scenarios, this is just a option.
>
> .
>
next prev parent reply other threads:[~2021-08-19 9:38 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-18 15:22 [PATCH] mm, vmscan: guarantee drop_slab_node() termination Vlastimil Babka
2021-08-18 21:48 ` Chris Down
2021-08-19 2:55 ` Kefeng Wang
2021-08-19 7:01 ` Vlastimil Babka
2021-08-19 9:38 ` Kefeng Wang [this message]
2021-08-19 13:21 ` Chris Down
2021-08-19 14:16 ` Michal Hocko
2021-08-24 9:33 ` Vlastimil Babka
2021-08-24 10:02 ` Matthew Wilcox
2021-08-24 14:04 ` Vlastimil Babka
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