From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751515AbdJCV4Q (ORCPT ); Tue, 3 Oct 2017 17:56:16 -0400 Received: from mail-wr0-f195.google.com ([209.85.128.195]:35223 "EHLO mail-wr0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750865AbdJCV4O (ORCPT ); Tue, 3 Oct 2017 17:56:14 -0400 X-Google-Smtp-Source: AOwi7QC8CYz7ARLd0zDPEOBpcoz1TTdGnNgaYgpdGxpkaLIHd8Le9l5wgnpWmVD6z++7rWomKFtGqg== Date: Wed, 4 Oct 2017 00:56:10 +0300 From: Alexey Dobriyan To: Gargi Sharma Cc: Oleg Nesterov , akpm@linux-foundation.org, "Eric W. Biederman" , keescook@chromium.org, mm-commits@vger.kernel.org, linux-kernel@vger.kernel.org, Rik van Riel Subject: Re: + pid-delete-struct-pidmap-nr_free.patch added to -mm tree Message-ID: <20171003215610.GB7023@avx2> References: <59d2c81b.sN3iiDcgxwFHtFRg%akpm@linux-foundation.org> <20171003161510.GB9929@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.7.2 (2016-11-26) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 03, 2017 at 11:09:08PM +0530, Gargi Sharma wrote: > On Tue, Oct 3, 2017 at 9:45 PM, Oleg Nesterov wrote: > > On 10/02, Andrew Morton wrote: > >> > >> From: Alexey Dobriyan > >> Subject: pid: delete struct pidmap::nr_free > >> > >> There is a check in pid allocation code to skip a full page: > >> > >> if (likely(atomic_read(&map->nr_free))) { > >> ... > >> > >> In practice it doesn't do anything. To skip a pidmap page one has to have > >> 32K consecutive pids allocated at the same time which doesn't happen. > >> > >> Currently the price is _every_ fork/exit on every system being slower than > >> necessary. > > > > Agreed, I too never understood how can this counter help. > > > > Add Gargi and Rik, the next version of "Replace PID bitmap allocation with IDR > > API" can conflict with this and the previous pid-delete-reserved_pids.patch. > > I think this patch will become obsolete as pidmap will be removed. As > for the 1/2 > patch of Alexey's series, I'll incorporate it so that rolled over PIDs ^^^^^^^^^^^ > start from 1 instead of RESERVED_PIDS. I saw IDR pids, lots of code removed indeed. Incorporation is not really necessary as RESERVED_PIDS is an independent change. Just send it as 2/2 or whatever the number or rebase on top of -mm.