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Tue, 3 Apr 2018 17:52:51 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:42400 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753340AbeDCVwu (ORCPT ); Tue, 3 Apr 2018 17:52:50 -0400 Date: Tue, 3 Apr 2018 14:52:48 -0700 From: Andrew Morton To: Nagarathnam Muthusamy Cc: linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, ebiederm@xmission.com, khlebnikov@yandex-team.ru, serge.hallyn@ubuntu.com, oleg@redhat.com, luto@amacapital.net, jannh@google.com, prakash.sangappa@oracle.com Subject: Re: [RESEND PATCH V4] pidns: introduce syscall translate_pid Message-Id: <20180403145248.fb4cd8c5ccd270ca77fd18f3@linux-foundation.org> In-Reply-To: <678f275b-8d78-9b0f-177f-5ff5c9c55657@oracle.com> References: <1522706249-11578-1-git-send-email-nagarathnam.muthusamy@oracle.com> <20180403143838.614ecc083835d07d409a699c@linux-foundation.org> <678f275b-8d78-9b0f-177f-5ff5c9c55657@oracle.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-api-owner@vger.kernel.org X-Mailing-List: linux-api@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Tue, 3 Apr 2018 14:45:28 -0700 Nagarathnam Muthusamy wrote: > > This changelog doesn't explain what the value is to our users. I > > assume it is a performance optimization because "backward translation > > requires scanning all tasks"? If so, please show us real-world > > examples of the performance benefit from this patch, and please go to > > great lengths to explain to us why this optimisation is needed by our > > users. > > One of the usecase by Oracle database involves multiple levels of > nested pid namespaces and we require pid translation between the > levels. Discussions on the particular usecase, why any of the existing > methods was not usable happened in the following thread. > > https://patchwork.kernel.org/patch/10276785/ > > At the end, it was agreed that this patch along with flocks will solve the > issue. Nobody who reads this patch's changelog will know any of this. Please let's get all this information into the proper place.