From: huang ying <huang.ying.caritas@gmail.com>
To: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>,
Hillf Danton <hdanton@sina.com>, Michal Hocko <mhocko@suse.com>,
Matthew Wilcox <willy@infradead.org>,
Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>,
Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH 2/2] mm/vmalloc: rework the drain logic
Date: Tue, 17 Nov 2020 10:37:34 +0800 [thread overview]
Message-ID: <CAC=cRTN77LAn-9-6rGukc2aUZQzx7oP9eKt_hJeb=wbnhGqObQ@mail.gmail.com> (raw)
In-Reply-To: <20201116220033.1837-2-urezki@gmail.com>
On Tue, Nov 17, 2020 at 6:00 AM Uladzislau Rezki (Sony)
<urezki@gmail.com> wrote:
>
> A current "lazy drain" model suffers from at least two issues.
>
> First one is related to the unsorted list of vmap areas, thus
> in order to identify the [min:max] range of areas to be drained,
> it requires a full list scan. What is a time consuming if the
> list is too long.
>
> Second one and as a next step is about merging all fragments
> with a free space. What is also a time consuming because it
> has to iterate over entire list which holds outstanding lazy
> areas.
>
> See below the "preemptirqsoff" tracer that illustrates a high
> latency. It is ~24 676us. Our workloads like audio and video
> are effected by such long latency:
This seems like a real problem. But I found there's long latency
avoidance mechanism in the loop in __purge_vmap_area_lazy() as
follows,
if (atomic_long_read(&vmap_lazy_nr) < resched_threshold)
cond_resched_lock(&free_vmap_area_lock);
If it works properly, the latency problem can be solved. Can you
check whether this doesn't work for you?
Best Reagrds,
Huang, Ying
<snip>
next prev parent reply other threads:[~2020-11-17 2:37 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-16 22:00 [PATCH 1/2] mm/vmalloc: use free_vm_area() if an allocation fails Uladzislau Rezki (Sony)
2020-11-16 22:00 ` [PATCH 2/2] mm/vmalloc: rework the drain logic Uladzislau Rezki (Sony)
2020-11-17 2:37 ` huang ying [this message]
2020-11-17 13:04 ` Uladzislau Rezki
2020-11-18 2:44 ` huang ying
2020-11-18 16:16 ` Uladzislau Rezki
2020-11-19 1:40 ` Huang, Ying
2020-11-19 17:36 ` Uladzislau Rezki
2020-11-20 2:34 ` Huang, Ying
2020-11-23 13:59 ` Uladzislau Rezki
2020-11-24 2:25 ` Huang, Ying
2020-11-24 16:40 ` Uladzislau Rezki
2020-11-25 0:52 ` Huang, Ying
2020-11-25 20:34 ` Uladzislau Rezki
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