netdev - Re: [PATCH V4] mlx4_core: allocate ICM memory in page size chunks

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Message-ID: <7d8f52e1-aa16-d20c-a9a8-35ad88c0b1ab@oracle.com>
Date:   Thu, 31 May 2018 19:04:46 -0700
From:   Qing Huang <qing.huang@...cle.com>
To:     Michal Hocko <mhocko@...nel.org>,
        Eric Dumazet <eric.dumazet@...il.com>
Cc:     David Miller <davem@...emloft.net>, tariqt@...lanox.com,
        haakon.bugge@...cle.com, yanjun.zhu@...cle.com,
        netdev@...r.kernel.org, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org, gi-oh.kim@...fitbricks.com,
        "santosh.shilimkar@...cle.com" <santosh.shilimkar@...cle.com>
Subject: Re: [PATCH V4] mlx4_core: allocate ICM memory in page size chunks



On 5/31/2018 2:10 AM, Michal Hocko wrote:
> On Thu 31-05-18 10:55:32, Michal Hocko wrote:
>> On Thu 31-05-18 04:35:31, Eric Dumazet wrote:
> [...]
>>> I merely copied/pasted from alloc_skb_with_frags() :/
>> I will have a look at it. Thanks!
> OK, so this is an example of an incremental development ;).
>
> __GFP_NORETRY was added by ed98df3361f0 ("net: use __GFP_NORETRY for
> high order allocations") to prevent from OOM killer. Yet this was
> not enough because fb05e7a89f50 ("net: don't wait for order-3 page
> allocation") didn't want an excessive reclaim for non-costly orders
> so it made it completely NOWAIT while it preserved __GFP_NORETRY in
> place which is now redundant. Should I send a patch?
>

Just curious, how about GFP_ATOMIC flag? Would it work in a similar 
fashion? We experimented
with it a bit in the past but it seemed to cause other issue in our 
tests. :-)

By the way, we didn't encounter any OOM killer events. It seemed that 
the mlx4_alloc_icm() triggered slowpath.
We still had about 2GB free memory while it was highly fragmented.

  #0 [ffff8801f308b380] remove_migration_pte at ffffffff811f0e0b
  #1 [ffff8801f308b3e0] rmap_walk_file at ffffffff811cb890
  #2 [ffff8801f308b440] rmap_walk at ffffffff811cbaf2
  #3 [ffff8801f308b450] remove_migration_ptes at ffffffff811f0db0
  #4 [ffff8801f308b490] __unmap_and_move at ffffffff811f2ea6
  #5 [ffff8801f308b4e0] unmap_and_move at ffffffff811f2fc5
  #6 [ffff8801f308b540] migrate_pages at ffffffff811f3219
  #7 [ffff8801f308b5c0] compact_zone at ffffffff811b707e
  #8 [ffff8801f308b650] compact_zone_order at ffffffff811b735d
  #9 [ffff8801f308b6e0] try_to_compact_pages at ffffffff811b7485
#10 [ffff8801f308b770] __alloc_pages_direct_compact at ffffffff81195f96
#11 [ffff8801f308b7b0] __alloc_pages_slowpath at ffffffff811978a1
#12 [ffff8801f308b890] __alloc_pages_nodemask at ffffffff81197ec1
#13 [ffff8801f308b970] alloc_pages_current at ffffffff811e261f
#14 [ffff8801f308b9e0] mlx4_alloc_icm at ffffffffa01f39b2 [mlx4_core]

Thanks!