linux-kernel - Re: [patch 113/131] mm: balance LRU lists based on relative thrashing

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Date:   Tue, 9 Jun 2020 10:45:51 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Alex Shi <alex.shi@...ux.alibaba.com>
Cc:     linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
        iamjoonsoo.kim@....com, linux-mm@...ck.org, mhocko@...e.com,
        minchan@...nel.org, mm-commits@...r.kernel.org, riel@...riel.com,
        torvalds@...ux-foundation.org
Subject: Re: [patch 113/131] mm: balance LRU lists based on relative thrashing

On Tue, Jun 09, 2020 at 05:15:33PM +0800, Alex Shi wrote:
> 
> 
> 在 2020/6/4 上午7:03, Andrew Morton 写道:
> >  
> > +	/* XXX: Move to lru_cache_add() when it supports new vs putback */
> 
> Hi Hannes,
> 
> Sorry for a bit lost, would you like to explain a bit more of your idea here?
> 
> > +	spin_lock_irq(&page_pgdat(page)->lru_lock);
> > +	lru_note_cost(page);
> > +	spin_unlock_irq(&page_pgdat(page)->lru_lock);
> > +
> 
> 
> What could we see here w/o the lru_lock?

It'll just be part of the existing LRU locking in
pagevec_lru_move_fn(), when the new pages are added to the LRU in
batch. See this older patch for example:

https://lore.kernel.org/linux-mm/20160606194836.3624-6-hannes@cmpxchg.org/

I didn't include it in this series to reduce conflict with Joonsoo's
WIP series that also operates in this area and does something similar:

https://lkml.org/lkml/2020/4/3/63