linux-kernel - Re: [PATCH 2/2] zram: idle memory tracking

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Message-ID: <20180327022635.GA74514@rodete-desktop-imager.corp.google.com>
Date:   Tue, 27 Mar 2018 11:26:35 +0900
From:   Minchan Kim <minchan@...nel.org>
To:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] zram: idle memory tracking

On Tue, Mar 27, 2018 at 11:21:26AM +0900, Sergey Senozhatsky wrote:
> On (03/26/18 15:49), Minchan Kim wrote:
> [..]
> > +static ssize_t read_access_time(struct file *file, char __user *buf,
> > +				size_t count, loff_t *ppos)
> > +{
> [..]
> > +
> > +	for (index = *ppos; index < nr_pages; index++) {
> > +		zram_slot_lock(zram, index);
> > +		if (zram_test_flag(zram, index, ZRAM_WB))
> > +			goto next;
> 
> I think it'll be better to show ZRAM_WB pages as well. Those pages
> are swapped out pages after all, consuming swap space - a physical
> page. Freeing those should also be beneficial. So tracking "bad"
> incompressible pages is quite handful.
> 
> > +		if (zram_test_flag(zram, index, ZRAM_SAME))
> > +			goto next;
> > +		if (!zram_get_handle(zram, index))
> > +			goto next;
> > +
> > +		ret = snprintf(kbuf + written, remained, "%lu %lu\n", index,
> > +				get_seconds() - zram->table[index].ac_time);
> 
> So here you can add a flag after index and age which will tell if the page
> is in zsmalloc pool or on backing swap device.

Yeb, that's the way I'm approach during our discussion!

Thanks for the review, Sergey!