From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mathieu Desnoyers Subject: Re: RCU consistency guarantees Date: Fri, 6 Dec 2019 10:59:05 -0500 (EST) Message-ID: <512711764.1078.1575647945136.JavaMail.zimbra__23192.7767208376$1575647964$gmane$org@efficios.com> References: <194534011.751.1575629349181.JavaMail.zimbra@efficios.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============7098162895546590200==" Return-path: Received: from mail.efficios.com (mail.efficios.com [167.114.142.138]) by lists.lttng.org (Postfix) with ESMTPS id 47Ty225Ndbz11tS for ; Fri, 6 Dec 2019 10:59:06 -0500 (EST) Received: from localhost (ip6-localhost [IPv6:::1]) by mail.efficios.com (Postfix) with ESMTP id 027D826F8E1 for ; Fri, 6 Dec 2019 10:59:06 -0500 (EST) In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: lttng-dev-bounces@lists.lttng.org Sender: "lttng-dev" To: Yuxin Ren Cc: lttng-dev , paulmck List-Id: lttng-dev@lists.lttng.org --===============7098162895546590200== Content-Type: multipart/alternative; boundary="=_a750b78c-95fb-445c-8c13-4664ffae9078" --=_a750b78c-95fb-445c-8c13-4664ffae9078 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable ----- On Dec 6, 2019, at 3:51 PM, Yuxin Ren wrote:=20 > On Fri, Dec 6, 2019 at 5:49 AM Mathieu Desnoyers < [ > mailto:mathieu.desnoyers@efficios.com | mathieu.desnoyers@efficios.com ] = > > wrote: >> ----- On Dec 5, 2019, at 8:17 PM, Yuxin Ren < [ mailto:ryx@gwmail.gwu.ed= u | >> ryx@gwmail.gwu.edu ] > wrote: >>> Hi, >>> I am a student, and learning RCU now, but still know very little about = it. >>> Are there any documents/papers/materials which (in)formally define and = explain >>> RCU consistency guarantees? >> You may want to have a look at >> User-Level Implementations of Read-Copy Update >> Article in IEEE Transactions on Parallel and Distributed Systems 23(2):3= 75 - 382 >> =C2=B7 March 2012 > Thanks for your info. > However, I do not think URCU talks about any consistency model formally. > From previous communication with Paul, he said RCU is not designed for > linearizability, and it is totally acceptable that RCU is not linearizabl= e. > However, I am curious how to accurately/formally Characterize RCU consist= ency > model/guarantees Adding Paul E. McKenney in CC.=20 I am referring to the section "Overview of RCU semantics" in the paper. Not= sure it has the level of=20 formality you are looking for though. Paul, do you have pointers to additio= nal material ?=20 Thanks,=20 Mathieu=20 >> as a starting point. >> Thanks, >> Mathieu >>> I know there are some consistency models in the database area (such as = PRAM, >>> Read Uncommitted, etc) from [ https://jepsen.io/consistency | >>> https://jepsen.io/consistency ] and [1]. >>> How does RCU related to those consistency models? >>> I also found some comments online (One key distinction is that both MVC= C and RLU >>> provide much stronger consistency guarantees to readers than does RCU .= ..) ( [ >>> https://lwn.net/Articles/777036/ | https://lwn.net/Articles/777036/ ] )= . >>> I do not understand how we reason/dresibe/compare the consistency guara= ntees. ( >>> I even do not know what consistency guarantees provided by RCU formally= ) >>> Could someone explain this to me? >>> [1] Bailis, P., Davidson, A., Fekete, A., Ghodsi, A., Hellerstein, J. M= ., & >>> Stoica, I. (2013). Highly available transactions: Virtues and limitatio= ns. >>> Proceedings of the VLDB Endowment, 7(3), 181-192. >>> Thanks >>> Yuxin >>> _______________________________________________ >>> lttng-dev mailing list >>> [ mailto:lttng-dev@lists.lttng.org | lttng-dev@lists.lttng.org ] >>> [ https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev | >>> https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev ] >> -- >> Mathieu Desnoyers >> EfficiOS Inc. >> [ http://www.efficios.com/ | http://www.efficios.com ] --=20 Mathieu Desnoyers=20 EfficiOS Inc.=20 http://www.efficios.com=20 --=_a750b78c-95fb-445c-8c13-4664ffae9078 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable

----- On Dec 6, 2019, at 3:51 PM, Y= uxin Ren <ryx@gwmail.gwu.edu> wrote:


On Fri, Dec 6, 2019 at 5:49 AM Mathieu Desnoyers <= mathieu.desnoyers@efficios.com> wrote:=

----- On Dec 5, 2019, at 8:17 PM, Yuxin Ren <ryx@gwma= il.gwu.edu> wrote:
Hi,
I am a student, and learning RCU now, but still know very = little about it.
Are there any documents/papers/materials which (= in)formally define and explain RCU consistency guarantees?
=

You may want to have a look at

User-Level Implementations of Read-Copy Update
Article=E2=80=82i= n=E2=80=82IEEE Transactions on Parallel and Distributed Systems 23(2):375 -= 382 =C2=B7 March 2012

T= hanks for your info.
However, I do not think URCU talks about any= consistency model formally. 

From previous co= mmunication with Paul, he said RCU is not designed for linea= rizability, and it is totally acceptable that RCU is not lineariz= able.
However, I am curious how to accurately/formally Chara= cterize RCU consistency model/guarantees
Adding Paul E. McKenney in CC.
I am referring to the section "Overview of= RCU semantics" in the paper. Not sure it has the level of
formality you are looking for though. Paul, do you have = pointers to additional material ?

Thanks,
Mathieu



as a starting point.
Thanks,

Mathieu


I know there are some consist= ency models in the database area (such as PRAM, Read Uncommitted, etc)= from https://jepse= n.io/consistency and [1].
How does RCU related to those = consistency models?

I also found some comments online (One ke= y distinction is that both MVCC and RLU provide much stronger consistency g= uarantees to readers than does RCU ...) (https://lwn.net/Articles/777036/).
I do n= ot understand how we reason/dresibe/compare the consistency guarantees= . ( I even do not know what consistency guarantees provided by RCU formally= )
Could someone explain this to me?
=