linux-kernel - Re: [virtio-dev] Re: [PATCH v13 4/5] mm: support reporting free page blocks

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Message-ID: <20170810070517.GB23863@dhcp22.suse.cz>
Date:   Thu, 10 Aug 2017 09:05:18 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Wei Wang <wei.w.wang@...el.com>
Cc:     linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, kvm@...r.kernel.org,
        linux-mm@...ck.org, mst@...hat.com, mawilcox@...rosoft.com,
        akpm@...ux-foundation.org, virtio-dev@...ts.oasis-open.org,
        david@...hat.com, cornelia.huck@...ibm.com,
        mgorman@...hsingularity.net, aarcange@...hat.com,
        amit.shah@...hat.com, pbonzini@...hat.com,
        liliang.opensource@...il.com, yang.zhang.wz@...il.com,
        quan.xu@...yun.com
Subject: Re: [virtio-dev] Re: [PATCH v13 4/5] mm: support reporting free page
 blocks

On Tue 08-08-17 14:34:25, Wei Wang wrote:
> On 08/08/2017 02:12 PM, Wei Wang wrote:
> >On 08/03/2017 05:11 PM, Michal Hocko wrote:
> >>On Thu 03-08-17 14:38:18, Wei Wang wrote:
> >>This is just too ugly and wrong actually. Never provide struct page
> >>pointers outside of the zone->lock. What I've had in mind was to simply
> >>walk free lists of the suitable order and call the callback for each
> >>one.
> >>Something as simple as
> >>
> >>    for (i = 0; i < MAX_NR_ZONES; i++) {
> >>        struct zone *zone = &pgdat->node_zones[i];
> >>
> >>        if (!populated_zone(zone))
> >>            continue;
> >
> >Can we directly use for_each_populated_zone(zone) here?

yes, my example couldn't because I was still assuming per-node API

> >>spin_lock_irqsave(&zone->lock, flags);
> >>        for (order = min_order; order < MAX_ORDER; ++order) {
> >
> >
> >This appears to be covered by for_each_migratetype_order(order, mt) below.

yes but
#define for_each_migratetype_order(order, type) \
	for (order = 0; order < MAX_ORDER; order++) \
		for (type = 0; type < MIGRATE_TYPES; type++)

so you would have to skip orders < min_order
-- 
Michal Hocko
SUSE Labs