linux-kernel - Re: [RFC PATCH 1/4] mm, hugetlb: unclutter hugetlb allocation layers

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Message-ID: <20170614152813.GR6045@dhcp22.suse.cz>
Date:   Wed, 14 Jun 2017 17:28:14 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     linux-mm@...ck.org, Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Mel Gorman <mgorman@...e.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 1/4] mm, hugetlb: unclutter hugetlb allocation layers

On Wed 14-06-17 17:06:47, Vlastimil Babka wrote:
> On 06/14/2017 03:42 PM, Michal Hocko wrote:
> > On Wed 14-06-17 15:18:26, Vlastimil Babka wrote:
> >> On 06/13/2017 11:00 AM, Michal Hocko wrote:
> > [...]
> >>> @@ -1717,13 +1640,22 @@ struct page *alloc_huge_page_node(struct hstate *h, int nid)
> >>>  		page = dequeue_huge_page_node(h, nid);
> >>>  	spin_unlock(&hugetlb_lock);
> >>>  
> >>> -	if (!page)
> >>> -		page = __alloc_buddy_huge_page_no_mpol(h, nid);
> >>> +	if (!page) {
> >>> +		nodemask_t nmask;
> >>> +
> >>> +		if (nid != NUMA_NO_NODE) {
> >>> +			nmask = NODE_MASK_NONE;
> >>> +			node_set(nid, nmask);
> >>
> >> TBH I don't like this hack too much, and would rather see __GFP_THISNODE
> >> involved, which picks a different (short) zonelist. Also it's allocating
> >> nodemask on stack, which we generally avoid? Although the callers
> >> currently seem to be shallow.
> > 
> > Fair enough. That would require pulling gfp mask handling up the call
> > chain. This on top of this patch + refreshes for other patches later in
> > the series as they will conflict now?
> 
> For the orig patch + fold (squashed locally from your mmotm/... branch)
> 
> Acked-by: Vlastimil Babka <vbabka@...e.cz>

Thanks!

> Please update the commit description which still mentions the nodemask
> emulation of __GFP_THISNODE.

yes I will do that when squashing them.

> Also I noticed that the goal of patch 2 is already partially achieved
> here, because alloc_huge_page_nodemask() will now allocate using
> zonelist. It won't dequeue that way yet, though.

well, the primary point if the later is to allow for the preferred node.
I didn't find a proper way to split the two things and still have a
reasonably comprehensible diff. So I've focused on the real allocation
here and pools in the other patch. Hope that makes some sense.
-- 
Michal Hocko
SUSE Labs