From: "Kasatkin, Dmitry" <dmitry.kasatkin@intel.com>
To: Eric Paris <eparis@parisplace.org>
Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>,
linux-security-module@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
David Safford <safford@watson.ibm.com>,
Mimi Zohar <zohar@us.ibm.com>
Subject: Re: [RFC][PATCH v1 5/9] ima: allocating iint improvements
Date: Thu, 9 Feb 2012 11:40:22 +0200 [thread overview]
Message-ID: <CALLzPKYnpAjgQ+LWJpKVkPkcwR5zs-uiLX2DMwiARNW8DtX0Ow@mail.gmail.com> (raw)
In-Reply-To: <CALLzPKZcr8fZ9-VXqLHN=H69+GOnp48CjZX+xxmBBksbmJsLxw@mail.gmail.com>
On Wed, Feb 1, 2012 at 8:46 PM, Kasatkin, Dmitry
<dmitry.kasatkin@intel.com> wrote:
> On Wed, Feb 1, 2012 at 6:58 PM, Eric Paris <eparis@parisplace.org> wrote:
>> On Mon, Jan 30, 2012 at 5:14 PM, Mimi Zohar <zohar@linux.vnet.ibm.com> wrote:
>>> From: Dmitry Kasatkin <dmitry.kasatkin@intel.com>
>>>
>>
>>> static struct rb_root integrity_iint_tree = RB_ROOT;
>>> -static DEFINE_SPINLOCK(integrity_iint_lock);
>>> +static DEFINE_RWLOCK(integrity_iint_lock);
>>> static struct kmem_cache *iint_cache __read_mostly;
>>
>> Has any profiling been done here? rwlocks have been shown to
>> actually be slower on multi processor systems in a number of cases due
>> to the cache line bouncing required. I believe the current kernel
>> logic is that if you have a short critical section and you can't show
>> profile data the rwlocks are better, just stick with a spinlock.
>
> No, I have not done any profiling.
> My assumption was that rwlocks are better when there many readers.
> If what you say is true then rwlocks are useless...
> With big sections it is necessary to use rw semaphores.
>
Hello,
I and Mimi made performance measurements with rwlocks and spinlocks.
We used kernel compilation with multiple jobs as a test,
because it reads and creates lots of files..
In all cases rwlocks implementation performed better than spinlocks,
but very insignificantly. For example with total compilation time
around 6 minutes, with rwlocks time was 1 - 3 seconds shorter... But
always like that.
So as conclusion I can make, that usage of rwlocks is justified...
Thanks for bringing this up...
> - Dmitry
next prev parent reply other threads:[~2012-02-09 9:40 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-30 22:13 [RFC][PATCH v1 0/9] ima: appraisal extension Mimi Zohar
2012-01-30 22:13 ` [RFC][PATCH v1 1/9] vfs: extend vfs_removexattr locking Mimi Zohar
2012-01-30 22:13 ` [RFC][PATCH v1 2/9] vfs: move ima_file_free before releasing the file Mimi Zohar
2012-01-30 22:13 ` [RFC][PATCH v1 3/9] ima: integrity appraisal extension Mimi Zohar
2012-01-30 22:13 ` [RFC][PATCH v1 4/9] ima: add appraise action keywords and default rules Mimi Zohar
2012-01-30 22:14 ` [RFC][PATCH v1 5/9] ima: allocating iint improvements Mimi Zohar
2012-02-01 16:58 ` Eric Paris
2012-02-01 18:46 ` Kasatkin, Dmitry
2012-02-09 9:40 ` Kasatkin, Dmitry [this message]
2012-01-30 22:14 ` [RFC][PATCH v1 6/9] ima: add inode_post_setattr call Mimi Zohar
2012-01-30 22:14 ` [RFC][PATCH v1 7/9] ima: add ima_inode_setxattr/removexattr function and calls Mimi Zohar
2012-01-30 22:14 ` [RFC][PATCH v1 8/9] ima: add support for different security.ima data types Mimi Zohar
2012-01-30 22:14 ` [RFC][PATCH v1 9/9] ima: digital signature verification support Mimi Zohar
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