From: Rik van Riel <riel@redhat.com>
To: rajman mekaco <rajman.mekaco@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Paul Gortmaker <paul.gortmaker@windriver.com>,
Andrew Morton <akpm@linux-foundation.org>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
Minchan Kim <minchan.kim@gmail.com>,
Christoph Lameter <cl@gentwo.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 1/1] mlock: split the shmlock_user_lock spinlock into per user_struct spinlock
Date: Thu, 10 May 2012 18:30:38 -0400 [thread overview]
Message-ID: <4FAC418E.6060500@redhat.com> (raw)
In-Reply-To: <CAMYGaxqxb=XR8R26h4e2URA2hG2M3j9V4u0DLJ9ifmkZKJa+eg@mail.gmail.com>
On 05/10/2012 11:39 AM, rajman mekaco wrote:
> On Thu, May 10, 2012 at 8:24 PM, Rik van Riel<riel@redhat.com> wrote:
>> On 05/10/2012 09:34 AM, rajman mekaco wrote:
>>
>>> Any updates on this ?
>>
>>
>> There is still no usecase to demonstrate a problem, so no real
>> justification to merge the patch. Coming up with such a usecase
>> is up to the submitter of the patch.
>
> Maybe you didn't read my last email:
> If 2 different user-mode processes executing on 2 CPUs under 2 different
> users want to access the same shared memory through the
> shmctl(SHM_LOCK) / shmget(SHM_HUGETLB) / usr_shm_lock
> primitives, they could compete/spin even though their user_structs
> are different.
>
> Can you please correct me if I am missing some crucial point of understanding ?
Mlock is a very very expensive operation.
Updating the mlock statistics is a very cheap operation.
Does this spinlock ever show up contention wise?
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WARNING: multiple messages have this Message-ID (diff)
From: Rik van Riel <riel@redhat.com>
To: rajman mekaco <rajman.mekaco@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Paul Gortmaker <paul.gortmaker@windriver.com>,
Andrew Morton <akpm@linux-foundation.org>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
Minchan Kim <minchan.kim@gmail.com>,
Christoph Lameter <cl@gentwo.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 1/1] mlock: split the shmlock_user_lock spinlock into per user_struct spinlock
Date: Thu, 10 May 2012 18:30:38 -0400 [thread overview]
Message-ID: <4FAC418E.6060500@redhat.com> (raw)
In-Reply-To: <CAMYGaxqxb=XR8R26h4e2URA2hG2M3j9V4u0DLJ9ifmkZKJa+eg@mail.gmail.com>
On 05/10/2012 11:39 AM, rajman mekaco wrote:
> On Thu, May 10, 2012 at 8:24 PM, Rik van Riel<riel@redhat.com> wrote:
>> On 05/10/2012 09:34 AM, rajman mekaco wrote:
>>
>>> Any updates on this ?
>>
>>
>> There is still no usecase to demonstrate a problem, so no real
>> justification to merge the patch. Coming up with such a usecase
>> is up to the submitter of the patch.
>
> Maybe you didn't read my last email:
> If 2 different user-mode processes executing on 2 CPUs under 2 different
> users want to access the same shared memory through the
> shmctl(SHM_LOCK) / shmget(SHM_HUGETLB) / usr_shm_lock
> primitives, they could compete/spin even though their user_structs
> are different.
>
> Can you please correct me if I am missing some crucial point of understanding ?
Mlock is a very very expensive operation.
Updating the mlock statistics is a very cheap operation.
Does this spinlock ever show up contention wise?
--
All rights reversed
next prev parent reply other threads:[~2012-05-10 22:30 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-03 17:34 [PATCH 1/1] mlock: split the shmlock_user_lock spinlock into per user_struct spinlock rajman mekaco
2012-05-03 17:34 ` rajman mekaco
2012-05-03 18:07 ` Rik van Riel
2012-05-03 18:07 ` Rik van Riel
2012-05-03 20:27 ` Rik van Riel
2012-05-03 20:27 ` Rik van Riel
2012-05-04 1:12 ` rajman mekaco
2012-05-04 1:12 ` rajman mekaco
2012-05-10 13:34 ` rajman mekaco
2012-05-10 13:34 ` rajman mekaco
2012-05-10 14:54 ` Rik van Riel
2012-05-10 14:54 ` Rik van Riel
2012-05-10 15:39 ` rajman mekaco
2012-05-10 15:39 ` rajman mekaco
2012-05-10 16:48 ` rajman mekaco
2012-05-10 16:48 ` rajman mekaco
2012-05-10 22:30 ` Rik van Riel [this message]
2012-05-10 22:30 ` Rik van Riel
2012-05-12 3:10 ` rajman mekaco
2012-05-12 3:10 ` rajman mekaco
2012-05-03 19:31 ` Peter Zijlstra
2012-05-03 19:31 ` Peter Zijlstra
2012-05-03 20:26 ` Rik van Riel
2012-05-03 20:26 ` Rik van Riel
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