linux-kernel - Re: [PATCH] mm: add MM_SWAPENTS and page table when calculate tasksize in lowmem

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Message-ID: <alpine.DEB.2.10.1602221647520.4688@chino.kir.corp.google.com>
Date:	Mon, 22 Feb 2016 16:50:09 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Xishi Qiu <qiuxishi@...wei.com>
cc:	"Figo.zhang" <figo1802@...il.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	arve@...roid.com, riandrews@...roid.com,
	devel@...verdev.osuosl.org, zhong jiang <zhongjiang@...wei.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux MM <linux-mm@...ck.org>
Subject: Re: [PATCH] mm: add MM_SWAPENTS and page table when calculate tasksize
 in lowmem_scan()

On Thu, 18 Feb 2016, Xishi Qiu wrote:

> How about kill more processes at one time?
> 
> Usually loading camera will alloc 300-500M memory immediately, so call lmk
> repeatedly is a waste of time.
> 
> And can we reclaim memory at one time instead of reclaim-alloc-reclaim-alloc...
> in this situation? e.g. use try_to_free_pages(), set nr_to_reclaim=300M
> 

I don't use the lmk myself and it's never been used on my phone, so I 
can't speak for the usecase.  However, killing more than one process at a 
time is generally a bad idea because it can allow processes to deplete 
memory reserves which may be small on these systems.  The lmk cannot be 
considered a hotpath, so waiting for a process to exit and free its memory 
for a small amount of time is generally not a bad trade-off when the 
alternative is to kill many processes (perhaps unnecessarily), open 
yourself up to livelock, and free memory that is potentially unneeded.