From mboxrd@z Thu Jan 1 00:00:00 1970 From: KOSAKI Motohiro Subject: Re: [PATCH v5] add MAP_UNLOCKED mmap flag Date: Thu, 14 Jan 2010 16:02:42 +0900 (JST) Message-ID: <20100114155229.6735.A69D9226@jp.fujitsu.com> References: <20100114092845.D719.A69D9226@jp.fujitsu.com> <20100114065008.GC18808@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20100114065008.GC18808-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Gleb Natapov Cc: kosaki.motohiro-+CUm20s59erQFUHtdCDX3A@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org List-Id: linux-api@vger.kernel.org > On Thu, Jan 14, 2010 at 09:31:03AM +0900, KOSAKI Motohiro wrote: > > > If application does mlockall(MCL_FUTURE) it is no longer possible to mmap > > > file bigger than main memory or allocate big area of anonymous memory > > > in a thread safe manner. Sometimes it is desirable to lock everything > > > related to program execution into memory, but still be able to mmap > > > big file or allocate huge amount of memory and allow OS to swap them on > > > demand. MAP_UNLOCKED allows to do that. > > > > > > Signed-off-by: Gleb Natapov > > > --- > > > > > > I get reports that people find this useful, so resending. > > > > This description is still wrong. It doesn't describe why this patch is useful. > > > I think the text above describes the feature it adds and its use > case quite well. Can you elaborate what is missing in your opinion, > or suggest alternative text please? My point is, introducing mmap new flags need strong and clearly use-case. All patch should have good benefit/cost balance. the code can describe the cost, but the benefit can be only explained by the patch description. I don't think this poor description explained bit benefit rather than cost. you should explain why this patch is useful and not just pretty toy.