linux-kernel - Re: [PATCH v3] memcg: Add memory.pressure

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Date:	Tue, 2 Apr 2013 21:00:40 -0700
From:	Anton Vorontsov <anton@...msg.org>
To:	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	cgroups@...r.kernel.org, Tejun Heo <tj@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Pekka Enberg <penberg@...nel.org>,
	Mel Gorman <mgorman@...e.de>,
	Glauber Costa <glommer@...allels.com>,
	Michal Hocko <mhocko@...e.cz>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	Luiz Capitulino <lcapitulino@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Thelen <gthelen@...gle.com>,
	Leonid Moiseichuk <leonid.moiseichuk@...ia.com>,
	KOSAKI Motohiro <kosaki.motohiro@...il.com>,
	Minchan Kim <minchan@...nel.org>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	John Stultz <john.stultz@...aro.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, linaro-kernel@...ts.linaro.org,
	patches@...aro.org, kernel-team@...roid.com
Subject: Re: [PATCH v3] memcg: Add memory.pressure_level events

On Wed, Mar 27, 2013 at 10:53:30AM +0900, Kamezawa Hiroyuki wrote:
[...]
> >+++ b/mm/memcontrol.c
> >@@ -49,6 +49,7 @@
> >  #include <linux/fs.h>
> >  #include <linux/seq_file.h>
> >  #include <linux/vmalloc.h>
> >+#include <linux/vmpressure.h>
> >  #include <linux/mm_inline.h>
> >  #include <linux/page_cgroup.h>
> >  #include <linux/cpu.h>
> >@@ -376,6 +377,9 @@ struct mem_cgroup {
> >  	atomic_t	numainfo_events;
> >  	atomic_t	numainfo_updating;
> >  #endif
> >+
> >+	struct vmpressure vmpr;
> >+
> 
> How about placing this just below "memsw_threshold" ?
> memory objects around there is not performance critical.

Yup, done.

[...]
> >+static const unsigned int vmpressure_win = SWAP_CLUSTER_MAX * 16;
> >+static const unsigned int vmpressure_level_med = 60;
> >+static const unsigned int vmpressure_level_critical = 95;
> >+static const unsigned int vmpressure_level_critical_prio = 3;
> >+
> more comments are welcomed...
> 
> I'm not against the numbers themselves but I'm not sure how these numbers are
> selected...I'm glad if you show some reasons in changelog or somewhere.

Sure, in v4 the numbers are described in the comments.

[...]
> >+static enum vmpressure_levels vmpressure_calc_level(unsigned int scanned,
> >+						    unsigned int reclaimed)
> >+{
> >+	unsigned long scale = scanned + reclaimed;
> >+	unsigned long pressure;
> >+
> >+	if (!scanned)
> >+		return VMPRESSURE_LOW;
> 
> Can you add comment here ? When !scanned happens ?

Yeah, the comment is needed. in v4 I added explanation for this case.

[...]
> >+	mutex_lock(&vmpr->sr_lock);
> >+	vmpr->scanned += scanned;
> >+	vmpr->reclaimed += reclaimed;
> >+	mutex_unlock(&vmpr->sr_lock);
> >+
> >+	if (scanned < vmpressure_win || work_pending(&vmpr->work))
> >+		return;
> >+	schedule_work(&vmpr->work);
> >+}
> 
> I'm not sure how other guys thinks but....could you place the definition
> of work_fn above calling it ? you call vmpressure_wk_fn(), right ?

Yup. OK, I rearranged the code a bit.

[...]
> >  	do {
> >+		vmpressure_prio(sc->gfp_mask, sc->target_mem_cgroup,
> >+				sc->priority);
> >  		sc->nr_scanned = 0;
> >  		aborted_reclaim = shrink_zones(zonelist, sc);
> >
> >
> 
> When you answers Andrew's comment and fix problems, feel free to add
> 
> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>

Thanks a lot for the reviews, Kamezawa!

Anton
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