From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pb0-f42.google.com (mail-pb0-f42.google.com [209.85.160.42]) by kanga.kvack.org (Postfix) with ESMTP id B485D6B0031 for ; Thu, 3 Apr 2014 10:08:29 -0400 (EDT) Received: by mail-pb0-f42.google.com with SMTP id rr13so1906039pbb.15 for ; Thu, 03 Apr 2014 07:08:29 -0700 (PDT) Received: from fgwmail6.fujitsu.co.jp (fgwmail6.fujitsu.co.jp. [192.51.44.36]) by mx.google.com with ESMTPS id q5si3126106pbh.444.2014.04.03.07.08.27 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Thu, 03 Apr 2014 07:08:28 -0700 (PDT) Received: from m4.gw.fujitsu.co.jp (unknown [10.0.50.74]) by fgwmail6.fujitsu.co.jp (Postfix) with ESMTP id E2D2C3EE0BC for ; Thu, 3 Apr 2014 23:08:26 +0900 (JST) Received: from smail (m4 [127.0.0.1]) by outgoing.m4.gw.fujitsu.co.jp (Postfix) with ESMTP id D47D745DECC for ; Thu, 3 Apr 2014 23:08:26 +0900 (JST) Received: from s4.gw.fujitsu.co.jp (s4.gw.nic.fujitsu.com [10.0.50.94]) by m4.gw.fujitsu.co.jp (Postfix) with ESMTP id AFC0345DECE for ; Thu, 3 Apr 2014 23:08:26 +0900 (JST) Received: from s4.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s4.gw.fujitsu.co.jp (Postfix) with ESMTP id A213B1DB803E for ; Thu, 3 Apr 2014 23:08:26 +0900 (JST) Received: from m1001.s.css.fujitsu.com (m1001.s.css.fujitsu.com [10.240.81.139]) by s4.gw.fujitsu.co.jp (Postfix) with ESMTP id 3E6B11DB8032 for ; Thu, 3 Apr 2014 23:08:26 +0900 (JST) Message-ID: <533D6B28.6070305@jp.fujitsu.com> Date: Thu, 03 Apr 2014 23:07:36 +0900 From: Kamezawa Hiroyuki MIME-Version: 1.0 Subject: Re: [PATCH] ipc,shm: disable shmmax and shmall by default References: <1396235199.2507.2.camel@buesod1.americas.hpqcorp.net> <20140331170546.3b3e72f0.akpm@linux-foundation.org> <1396371699.25314.11.camel@buesod1.americas.hpqcorp.net> <1396377083.25314.17.camel@buesod1.americas.hpqcorp.net> <1396386062.25314.24.camel@buesod1.americas.hpqcorp.net> <20140401142947.927642a408d84df27d581e36@linux-foundation.org> <20140401144801.603c288674ab8f417b42a043@linux-foundation.org> <1396394931.25314.34.camel@buesod1.americas.hpqcorp.net> <1396484447.2953.1.camel@buesod1.americas.hpqcorp.net> In-Reply-To: <1396484447.2953.1.camel@buesod1.americas.hpqcorp.net> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Davidlohr Bueso , KOSAKI Motohiro Cc: Andrew Morton , Manfred Spraul , aswin@hp.com, LKML , "linux-mm@kvack.org" , Greg Thelen (2014/04/03 9:20), Davidlohr Bueso wrote: > The default size for shmmax is, and always has been, 32Mb. > Today, in the XXI century, it seems that this value is rather small, > making users have to increase it via sysctl, which can cause > unnecessary work and userspace application workarounds[1]. > > Instead of choosing yet another arbitrary value, larger than 32Mb, > this patch disables the use of both shmmax and shmall by default, > allowing users to create segments of unlimited sizes. Users and > applications that already explicitly set these values through sysctl > are left untouched, and thus does not change any of the behavior. > > So a value of 0 bytes or pages, for shmmax and shmall, respectively, > implies unlimited memory, as opposed to disabling sysv shared memory. > This is safe as 0 cannot possibly be used previously as SHMMIN is > hardcoded to 1 and cannot be modified. > > This change allows Linux to treat shm just as regular anonymous memory. > One important difference between them, though, is handling out-of-memory > conditions: as opposed to regular anon memory, the OOM killer will not > kill processes that are hogging memory through shm, allowing users to > potentially abuse this. To overcome this situation, the shm_rmid_forced > option must be enabled. > > Running this patch through LTP, everything passes, except the following, > which, due to the nature of this change, is quite expected: > > shmget02 1 TFAIL : call succeeded unexpectedly > > [1]: http://rhaas.blogspot.com/2012/06/absurd-shared-memory-limits.html > > Signed-off-by: Davidlohr Bueso looks good to me Acked-by: KAMEZAWA Hiroyuki When this goes mainline, updating a man page of ipcs may be required. Thanks, -Kame > --- > include/linux/shm.h | 2 +- > include/uapi/linux/shm.h | 8 ++++---- > ipc/shm.c | 6 ++++-- > 3 files changed, 9 insertions(+), 7 deletions(-) > > diff --git a/include/linux/shm.h b/include/linux/shm.h > index 1e2cd2e..0ca06a3 100644 > --- a/include/linux/shm.h > +++ b/include/linux/shm.h > @@ -4,7 +4,7 @@ > #include > #include > > -#define SHMALL (SHMMAX/PAGE_SIZE*(SHMMNI/16)) /* max shm system wide (pages) */ > +#define SHMALL 0 /* max shm system wide (pages) */ > #include > struct shmid_kernel /* private to the kernel */ > { > diff --git a/include/uapi/linux/shm.h b/include/uapi/linux/shm.h > index 78b6941..5f0ef28 100644 > --- a/include/uapi/linux/shm.h > +++ b/include/uapi/linux/shm.h > @@ -9,14 +9,14 @@ > > /* > * SHMMAX, SHMMNI and SHMALL are upper limits are defaults which can > - * be increased by sysctl > + * be increased by sysctl. By default, disable SHMMAX and SHMALL with > + * 0 bytes, thus allowing processes to have unlimited shared memory. > */ > - > -#define SHMMAX 0x2000000 /* max shared seg size (bytes) */ > +#define SHMMAX 0 /* max shared seg size (bytes) */ > #define SHMMIN 1 /* min shared seg size (bytes) */ > #define SHMMNI 4096 /* max num of segs system wide */ > #ifndef __KERNEL__ > -#define SHMALL (SHMMAX/getpagesize()*(SHMMNI/16)) > +#define SHMALL 0 > #endif > #define SHMSEG SHMMNI /* max shared segs per process */ > > diff --git a/ipc/shm.c b/ipc/shm.c > index 7645961..ae01ffa 100644 > --- a/ipc/shm.c > +++ b/ipc/shm.c > @@ -490,10 +490,12 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params) > int id; > vm_flags_t acctflag = 0; > > - if (size < SHMMIN || size > ns->shm_ctlmax) > + if (ns->shm_ctlmax && > + (size < SHMMIN || size > ns->shm_ctlmax)) > return -EINVAL; > > - if (ns->shm_tot + numpages > ns->shm_ctlall) > + if (ns->shm_ctlall && > + ns->shm_tot + numpages > ns->shm_ctlall) > return -ENOSPC; > > shp = ipc_rcu_alloc(sizeof(*shp)); > -- 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