linux-kernel - Re: [RFC PATCH 0/2] Add predictive memory reclamation and compaction

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Message-ID: <20190828131501.GK28313@dhcp22.suse.cz>
Date:   Wed, 28 Aug 2019 15:15:01 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Bharath Vedartham <linux.bhar@...il.com>
Cc:     Khalid Aziz <khalid.aziz@...cle.com>, akpm@...ux-foundation.org,
        vbabka@...e.cz, mgorman@...hsingularity.net,
        dan.j.williams@...el.com, osalvador@...e.de,
        richard.weiyang@...il.com, hannes@...xchg.org,
        arunks@...eaurora.org, rppt@...ux.vnet.ibm.com, jgg@...pe.ca,
        amir73il@...il.com, alexander.h.duyck@...ux.intel.com,
        linux-mm@...ck.org, linux-kernel-mentees@...ts.linuxfoundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 0/2] Add predictive memory reclamation and compaction

On Wed 28-08-19 18:39:22, Bharath Vedartham wrote:
[...]
> > Therefore I would like to shift the discussion towards existing APIs and
> > whether they are suitable for such an advance auto-tuning. I haven't
> > heard any arguments about missing pieces.
> I understand your concern here. Just confirming, by APIs you are
> referring to sysctls, sysfs files and stuff like that right?

Yup

> > > If memory exhaustion
> > > occurs, we reclaim some more memory. kswapd stops reclaim when
> > > hwmark is reached. hwmark is usually set to a fairly low percentage of
> > > total memory, in my system for zone Normal hwmark is 13% of total pages.
> > > So there is scope for reclaiming more pages to make sure system does not
> > > suffer from a lack of pages. 
> > 
> > Yes and we have ways to control those watermarks that your monitoring
> > tool can use to alter the reclaim behavior.
> Just to confirm here, I am aware of one way which is to alter
> min_kfree_bytes values. What other ways are there to alter watermarks
> from user space? 

/proc/sys/vm/watermark_*factor
-- 
Michal Hocko
SUSE Labs