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

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Message-ID: <4f1bc4dc65117a185833555ff8df30a944453499.camel@intel.com>
Date:   Fri, 22 Apr 2022 14:27:45 +0800
From:   "ying.huang@...el.com" <ying.huang@...el.com>
To:     Aaron Lu <aaron.lu@...el.com>
Cc:     Yang Shi <shy828301@...il.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 Fri, 2022-04-22 at 14:24 +0800, Aaron Lu 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.

The test case looks good to me.  And, do you have a way to measure swap
in latency?  Better to compare between enabling and disabling per-node
swap device support too to make sure per-node support has performance
impact on this system.

Best Regards,
Huang, Ying