linux-kernel - Re: [PATCH 0/2] psi: enhance psi with the help of ebpf

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Date:   Thu, 26 Mar 2020 10:31:02 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Yafang Shao <laoar.shao@...il.com>
Cc:     peterz@...radead.org, akpm@...ux-foundation.org, mhocko@...nel.org,
        axboe@...nel.dk, mgorman@...e.de, rostedt@...dmis.org,
        mingo@...hat.com, linux-mm@...ck.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] psi: enhance psi with the help of ebpf

On Thu, Mar 26, 2020 at 07:12:05AM -0400, Yafang Shao wrote:
> PSI gives us a powerful way to anaylze memory pressure issue, but we can
> make it more powerful with the help of tracepoint, kprobe, ebpf and etc.
> Especially with ebpf we can flexiblely get more details of the memory
> pressure.
> 
> In orderc to achieve this goal, a new parameter is added into
> psi_memstall_{enter, leave}, which indicates the specific type of a
> memstall. There're totally ten memstalls by now,
>         MEMSTALL_KSWAPD
>         MEMSTALL_RECLAIM_DIRECT
>         MEMSTALL_RECLAIM_MEMCG
>         MEMSTALL_RECLAIM_HIGH
>         MEMSTALL_KCOMPACTD
>         MEMSTALL_COMPACT
>         MEMSTALL_WORKINGSET_REFAULT
>         MEMSTALL_WORKINGSET_THRASHING
>         MEMSTALL_MEMDELAY
>         MEMSTALL_SWAPIO

What does this provide over the events tracked in /proc/vmstats?

Can you elaborate a bit how you are using this information? It's not
quite clear to me from the example in patch #2.