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From: Nicolas Dichtel <nicolas.dichtel@6wind.com>
To: Stephen Hemminger <stephen@networkplumber.org>
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	davem@davemloft.net, ebiederm@xmission.com,
	akpm@linux-foundation.org, adobriyan@gmail.com,
	rui.xiang@huawei.com, viro@zeniv.linux.org.uk, oleg@redhat.com,
	gorcunov@openvz.org, kirill.shutemov@linux.intel.com,
	grant.likely@secretlab.ca, tytso@mit.edu,
	Thierry Herbelot <thierry.herbelot@6wind.com>
Subject: Re: [RFC PATCH linux 2/2] fs/proc: use a hash table for the directory entries
Date: Fri, 03 Oct 2014 15:10:51 +0200	[thread overview]
Message-ID: <542EA05B.4010107@6wind.com> (raw)
In-Reply-To: <20141002094657.1e28e027@urahara>

Le 02/10/2014 18:46, Stephen Hemminger a écrit :
> On Thu,  2 Oct 2014 17:25:01 +0200
> Nicolas Dichtel <nicolas.dichtel@6wind.com> wrote:
>
>> From: Thierry Herbelot <thierry.herbelot@6wind.com>
>>
>> The current implementation for the directories in /proc is using a single
>> linked list. This is slow when handling directories with large numbers of
>> entries (eg netdevice-related entries when lots of tunnels are opened).
>>
>> This patch enables multiple linked lists. A hash based on the entry name is
>> used to select the linked list for one given entry.
>>
>> The speed creation of netdevices is faster as shorter linked lists must be
>> scanned when adding a new netdevice.
>>
>> Here are some numbers:
>>
>> dummy30000.batch contains 30 000 times 'link add type dummy'.
>>
>> Before the patch:
>> time ip -b dummy30000.batch
>> real    2m32.221s
>> user    0m0.380s
>> sys     2m30.610s
>>
>> After the patch:
>> time ip -b dummy30000.batch
>> real    1m57.190s
>> user    0m0.350s
>> sys     1m56.120s
>>
>> The single 'subdir' list head is replaced by a subdir hash table. The subdir
>> hash buckets are only allocated for directories. The number of hash buckets
>> is a compile-time parameter.
>>
>> For all functions which handle directory entries, an additional check on the
>> directory nature of the dir entry ensures that pde_hash_buckets was allocated.
>> This check was not needed as subdir was present for all dir entries, whether
>> actual directories or simple files.
>>
>> Signed-off-by: Thierry Herbelot <thierry.herbelot@6wind.com>
>> Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
>
> I think the speed up is a good idea and makes sense.
> It would be better to use exist hlist macros for hash table rather than
> open coding it.
>
Right, I will rework this after looking at rbtree.

  reply	other threads:[~2014-10-03 13:10 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20131003.150947.2179820478039260398.davem@davemloft.net>
2014-10-02 15:24 ` [RFC PATCH linux 0/2] Optimize network interfaces creation Nicolas Dichtel
2014-10-02 15:25   ` [RFC PATCH linux 1/2] proc_net: declare /proc/net as a directory Nicolas Dichtel
2014-10-02 15:25   ` [RFC PATCH linux 2/2] fs/proc: use a hash table for the directory entries Nicolas Dichtel
2014-10-02 16:46     ` Stephen Hemminger
2014-10-03 13:10       ` Nicolas Dichtel [this message]
2014-10-02 17:28     ` Alexey Dobriyan
2014-10-03 13:07       ` Nicolas Dichtel
2014-10-02 18:01     ` Eric W. Biederman
2014-10-02 20:06       ` Alexey Dobriyan
2014-10-02 21:07         ` Eric W. Biederman
2014-10-02 21:27           ` Stephen Hemminger
2014-10-03  7:28           ` Nicolas Dichtel
2014-10-03 13:09       ` Nicolas Dichtel
2014-10-06 14:30         ` [PATCH linux v2 0/1] Optimize network interfaces creation Nicolas Dichtel
2014-10-06 14:30           ` [PATCH linux v2 1/1] fs/proc: use a rb tree for the directory entries Nicolas Dichtel
2014-10-06 22:14             ` David Miller
2014-10-07  9:02               ` [PATCH linux v3 0/1] Optimize network interfaces creation Nicolas Dichtel
2014-10-07  9:02                 ` [PATCH linux v3 1/1] fs/proc: use a rb tree for the directory entries Nicolas Dichtel
2014-10-13 11:14                   ` Nicolas Dichtel
2014-10-14 19:30                     ` David Miller
2014-10-14 19:56                     ` Eric W. Biederman
2014-10-15  9:02                       ` Nicolas Dichtel
2014-10-15 21:37                   ` Andrew Morton
2014-10-03 10:55     ` [RFC PATCH linux 2/2] fs/proc: use a hash table " Alexey Dobriyan
2014-10-03 13:07       ` Nicolas Dichtel

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