linux-kernel - Re: [PATCH] mm: swap: determine swap device by using page nid

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Message-ID: <CAHbLzkriO6xWzyMNpcVFmyxSn=cqbz2qx+2mJ5d0m-beqPRCUg@mail.gmail.com>
Date:   Fri, 22 Apr 2022 10:00:59 -0700
From:   Yang Shi <shy828301@...il.com>
To:     Aaron Lu <aaron.lu@...el.com>
Cc:     "ying.huang@...el.com" <ying.huang@...el.com>,
        Michal Hocko <mhocko@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: swap: determine swap device by using page nid

On Thu, Apr 21, 2022 at 11:24 PM Aaron Lu <aaron.lu@...el.com> wrote:
>
> On Thu, Apr 21, 2022 at 04:34:09PM +0800, ying.huang@...el.com wrote:
> > On Thu, 2022-04-21 at 16:17 +0800, Aaron Lu wrote:
> > > On Thu, Apr 21, 2022 at 03:49:21PM +0800, ying.huang@...el.com wrote:
>
> ... ...
>
> > > > For swap-in latency, we can use pmbench, which can output latency
> > > > information.
> > > >
> > >
> > > OK, I'll give pmbench a run, thanks for the suggestion.
> >
> > Better to construct a senario with more swapin than swapout.  For
> > example, start a memory eater, then kill it later.
>
> What about vm-scalability/case-swapin?
> https://git.kernel.org/pub/scm/linux/kernel/git/wfg/vm-scalability.git/tree/case-swapin
>
> I think you are pretty familiar with it but still:
> 1) it starts $nr_task processes and each mmaps $size/$nr_task area and
>    then consumes the memory, after this, it waits for a signal;
> 2) start another process to consume $size memory to push the memory in
>    step 1) to swap device;
> 3) kick processes in step 1) to start accessing their memory, thus
>    trigger swapins. The metric of this testcase is the swapin throughput.
>
> I plan to restrict the cgroup's limit to $size.
>
> Considering there is only one NVMe drive attached to node 0, I will run
> the test as described before:
> 1) bind processes to run on node 0, allocate on node 1 to test the
>    performance when reclaimer's node id is the same as swap device's.
> 2) bind processes to run on node 1, allocate on node 0 to test the
>    performance when page's node id is the same as swap device's.
>
> Ying and Yang,
>
> Let me know what you think about the case used and the way the test is
> conducted.

Looks fine to me. To measure the latency, you could also try the below
bpftrace script:

#! /usr/bin/bpftrace

kprobe:swap_readpage
{
        @start[tid] = nsecs;
}

kretprobe:swap_readpage
/@...rt[tid]/
{
        @us[comm] = hist((nsecs - @start[tid]) / 1000);
        delete(@start[tid]);
}