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From: Eric Dumazet <eric.dumazet@gmail.com>
To: SeongJae Park <sjpark@amazon.com>, Eric Dumazet <edumazet@google.com>
Cc: David Miller <davem@davemloft.net>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Jakub Kicinski <kuba@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	sj38.park@gmail.com, netdev <netdev@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	SeongJae Park <sjpark@amazon.de>,
	snu@amazon.com, amit@kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH net v2 0/2] Revert the 'socket_alloc' life cycle change
Date: Tue, 5 May 2020 08:20:50 -0700	[thread overview]
Message-ID: <a8510327-d4f0-1207-1342-d688e9d5b8c3@gmail.com> (raw)
In-Reply-To: <20200505150717.5688-1-sjpark@amazon.com>



On 5/5/20 8:07 AM, SeongJae Park wrote:
> On Tue, 5 May 2020 07:53:39 -0700 Eric Dumazet <edumazet@google.com> wrote:
> 

>> Why do we have 10,000,000 objects around ? Could this be because of
>> some RCU problem ?
> 
> Mainly because of a long RCU grace period, as you guess.  I have no idea how
> the grace period became so long in this case.
> 
> As my test machine was a virtual machine instance, I guess RCU readers
> preemption[1] like problem might affected this.
> 
> [1] https://www.usenix.org/system/files/conference/atc17/atc17-prasad.pdf
> 
>>
>> Once Al patches reverted, do you have 10,000,000 sock_alloc around ?
> 
> Yes, both the old kernel that prior to Al's patches and the recent kernel
> reverting the Al's patches didn't reproduce the problem.
>

I repeat my question : Do you have 10,000,000 (smaller) objects kept in slab caches ?

TCP sockets use the (very complex, error prone) SLAB_TYPESAFE_BY_RCU, but not the struct socket_wq
object that was allocated in sock_alloc_inode() before Al patches.

These objects should be visible in kmalloc-64 kmem cache.


  reply	other threads:[~2020-05-05 15:20 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-05  8:10 [PATCH net v2 0/2] Revert the 'socket_alloc' life cycle change SeongJae Park
2020-05-05  8:10 ` [PATCH net v2 1/2] Revert "coallocate socket_wq with socket itself" SeongJae Park
2020-05-06  4:55   ` kbuild test robot
2020-05-06  4:55     ` kbuild test robot
2020-05-05  8:10 ` [PATCH net v2 2/2] Revert "sockfs: switch to ->free_inode()" SeongJae Park
2020-05-05 11:54 ` [PATCH net v2 0/2] Revert the 'socket_alloc' life cycle change SeongJae Park
2020-05-05 12:31   ` Nuernberger, Stefan
2020-05-05 14:53   ` Eric Dumazet
2020-05-05 15:07     ` SeongJae Park
2020-05-05 15:20       ` Eric Dumazet [this message]
2020-05-05 15:46         ` SeongJae Park
2020-05-05 16:00           ` Eric Dumazet
2020-05-05 16:13             ` SeongJae Park
2020-05-05 16:25               ` Eric Dumazet
2020-05-05 16:31                 ` Eric Dumazet
2020-05-05 16:37                   ` Eric Dumazet
2020-05-05 17:05                     ` SeongJae Park
2020-05-05 17:30                       ` Paul E. McKenney
2020-05-05 17:56                         ` SeongJae Park
2020-05-05 18:17                           ` Paul E. McKenney
2020-05-05 18:34                             ` SeongJae Park
2020-05-05 18:49                               ` Paul E. McKenney
2020-05-06 12:59                                 ` SeongJae Park
2020-05-06 14:33                                   ` Eric Dumazet
2020-05-06 14:41                                   ` Paul E. McKenney
2020-05-06 15:20                                     ` SeongJae Park
2020-05-05 17:28                     ` Paul E. McKenney
2020-05-05 18:11                       ` SeongJae Park
2020-05-05 17:23                 ` Paul E. McKenney
2020-05-05 17:49                   ` SeongJae Park
2020-05-05 18:27                     ` Paul E. McKenney
2020-05-05 18:40                       ` SeongJae Park
2020-05-05 18:48                         ` Paul E. McKenney
2020-05-05 16:26             ` Al Viro
2020-05-05 18:48 ` David Miller
2020-05-05 19:00   ` David Miller
2020-05-06  6:24     ` SeongJae Park

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