linux-kernel - Re: [PATCH 3/3] hugetlbfs: don't retry when pool page allocations start to fail

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Date:   Mon, 5 Aug 2019 11:28:04 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Mike Kravetz <mike.kravetz@...cle.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Cc:     Hillf Danton <hdanton@...a.com>, Michal Hocko <mhocko@...nel.org>,
        Mel Gorman <mgorman@...e.de>,
        Johannes Weiner <hannes@...xchg.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        David Rientjes <rientjes@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 3/3] hugetlbfs: don't retry when pool page allocations
 start to fail

On 8/3/19 12:39 AM, Mike Kravetz wrote:
> When allocating hugetlbfs pool pages via /proc/sys/vm/nr_hugepages,
> the pages will be interleaved between all nodes of the system.  If
> nodes are not equal, it is quite possible for one node to fill up
> before the others.  When this happens, the code still attempts to
> allocate pages from the full node.  This results in calls to direct
> reclaim and compaction which slow things down considerably.
> 
> When allocating pool pages, note the state of the previous allocation
> for each node.  If previous allocation failed, do not use the
> aggressive retry algorithm on successive attempts.  The allocation
> will still succeed if there is memory available, but it will not try
> as hard to free up memory.
> 
> Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>

Looks like only part of the (agreed with) suggestions were implemented?
- set_max_huge_pages() returns -ENOMEM if nodemask can't be allocated,
but hugetlb_hstate_alloc_pages() doesn't.
- there's still __GFP_NORETRY in nodemask allocations
- (cosmetics) Mel pointed out that NODEMASK_FREE() works fine with NULL
pointers

Thanks,
Vlastimil