From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753703AbdKXQuo convert rfc822-to-8bit (ORCPT ); Fri, 24 Nov 2017 11:50:44 -0500 Received: from mondschein.lichtvoll.de ([194.150.191.11]:52009 "EHLO mail.lichtvoll.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753524AbdKXQun (ORCPT ); Fri, 24 Nov 2017 11:50:43 -0500 From: Martin Steigerwald To: Matthew Wilcox Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Matthew Wilcox Subject: Re: XArray documentation Date: Fri, 24 Nov 2017 17:50:41 +0100 Message-ID: <3543098.x2GeNdvaH7@merkaba> In-Reply-To: <20171124011607.GB3722@bombadil.infradead.org> References: <20171122210739.29916-1-willy@infradead.org> <20171124011607.GB3722@bombadil.infradead.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8BIT Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello Matthew. Matthew Wilcox - 24.11.17, 02:16: > ====== > XArray > ====== > > Overview > ======== > > The XArray is an array of ULONG_MAX entries. Each entry can be either > a pointer, or an encoded value between 0 and LONG_MAX. It is efficient > when the indices used are densely clustered; hashing the object and > using the hash as the index will not perform well. A freshly-initialised > XArray contains a NULL pointer at every index. There is no difference > between an entry which has never been stored to and an entry which has most > recently had NULL stored to it. I am no kernel developer (just provided a tiny bit of documentation a long time ago)… but on reading into this, I missed: What is it about? And what is it used for? "Overview" appears to be already a description of the actual implementation specifics, instead of… well an overview. Of course, I am sure you all know what it is for… but someone who wants to learn about the kernel is likely to be confused by such a start. Thanks, -- Martin From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Martin Steigerwald To: Matthew Wilcox Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Matthew Wilcox Subject: Re: XArray documentation Date: Fri, 24 Nov 2017 17:50:41 +0100 Message-ID: <3543098.x2GeNdvaH7@merkaba> In-Reply-To: <20171124011607.GB3722@bombadil.infradead.org> References: <20171122210739.29916-1-willy@infradead.org> <20171124011607.GB3722@bombadil.infradead.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-mm@kvack.org List-ID: Hello Matthew. Matthew Wilcox - 24.11.17, 02:16: > =3D=3D=3D=3D=3D=3D > XArray > =3D=3D=3D=3D=3D=3D >=20 > Overview > =3D=3D=3D=3D=3D=3D=3D=3D >=20 > The XArray is an array of ULONG_MAX entries. Each entry can be either > a pointer, or an encoded value between 0 and LONG_MAX. It is efficient > when the indices used are densely clustered; hashing the object and > using the hash as the index will not perform well. A freshly-initialised > XArray contains a NULL pointer at every index. There is no difference > between an entry which has never been stored to and an entry which has mo= st > recently had NULL stored to it. I am no kernel developer (just provided a tiny bit of documentation a long= =20 time ago)=E2=80=A6 but on reading into this, I missed: What is it about? And what is it used for? "Overview" appears to be already a description of the actual implementation= =20 specifics, instead of=E2=80=A6 well an overview. Of course, I am sure you all know what it is for=E2=80=A6 but someone who w= ants to=20 learn about the kernel is likely to be confused by such a start. Thanks, =2D-=20 Martin -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org