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Date: Thu, 27 Oct 2011 12:44:30 -0400
From: Joe Korty <joe.korty@...r.com>
To: KOSAKI Motohiro <kosaki.motohiro@...il.com>
Cc: "dledford@...hat.com" <dledford@...hat.com>,
"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
"torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"amwang@...hat.com" <amwang@...hat.com>
Subject: Re: [PATCH 7/4] ipc/mqueue: separate mqueue default value from maximum value
On Wed, Oct 26, 2011 at 11:38:35AM -0400, KOSAKI Motohiro wrote:
> commit b231cca438 (message queues: increase range limits)
> changed mqueue default value when attr parameter is specified NULL
> from hard coded value to fs.mqueue.{msg,msgsize}_max sysctl value.
>
> This made large side effect. When user need to use two mqueue
> applications 1) using !NULL attr parameter and it require big
> message size and 2) using NULL attr parameter and only need small
> size message, app (1) require to raise fs.mqueue.msgsize_max and
> app (2) consume large memory size even though it doesn't need.
>
> Doug Ledford propsed to switch back it to static hard coded value.
> However it also has a compatibility problem. Some applications might
> started depend on the default value is tunable.
>
> The solution is to separate default value from maximum value.
>
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...il.com>
> Cc: Doug Ledford <dledford@...hat.com>
> Cc: Amerigo Wang <amwang@...hat.com>
> Cc: Serge E. Hallyn <serue@...ibm.com>
> Cc: Jiri Slaby <jslaby@...e.cz>
> Cc: Joe Korty <joe.korty@...r.com>
> ---
> Documentation/sysctl/fs.txt | 7 +++++++
> include/linux/ipc_namespace.h | 3 +++
> ipc/mq_sysctl.c | 18 ++++++++++++++++++
> ipc/mqueue.c | 9 ++++++---
> ipc/msgutil.c | 2 ++
> 5 files changed, 36 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/sysctl/fs.txt b/Documentation/sysctl/fs.txt
> index 88fd7f5..13d6166 100644
> --- a/Documentation/sysctl/fs.txt
> +++ b/Documentation/sysctl/fs.txt
> @@ -225,6 +225,13 @@ a queue must be less or equal then msg_max.
> maximum message size value (it is every message queue's attribute set during
> its creation).
>
> +/proc/sys/fs/mqueue/msg_default is a read/write file for setting/getting the
> +default number of messages in a queue value if attr parameter of mq_open(2) is
> +NULL. If it exceed msg_max, the default value is initialized msg_max.
> +
> +/proc/sys/fs/mqueue/msgsize_default is a read/write file for setting/getting
> +the default message size value if attr parameter of mq_open(2) is NULL. If it
> +exceed msgsize_max, the default value is initialized msgsize_max.
>
> 4. /proc/sys/fs/epoll - Configuration options for the epoll interface
> --------------------------------------------------------
Very much needed; maximums applied as defaults was a
bad idea.
Acked-by: Joe Korty <joe.korty@...r.com>
> diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h
> index 2d7c5e0..9e25a33 100644
> --- a/include/linux/ipc_namespace.h
> +++ b/include/linux/ipc_namespace.h
> @@ -63,6 +63,9 @@ struct ipc_namespace {
> unsigned int mq_msg_max; /* initialized to DFLT_MSGMAX */
> unsigned int mq_msgsize_max; /* initialized to DFLT_MSGSIZEMAX */
>
> + unsigned int mq_msg_default;
> + unsigned int mq_msgsize_default;
> +
> /* user_ns which owns the ipc ns */
> struct user_namespace *user_ns;
> };
> diff --git a/ipc/mq_sysctl.c b/ipc/mq_sysctl.c
> index e22336a..383d638 100644
> --- a/ipc/mq_sysctl.c
> +++ b/ipc/mq_sysctl.c
> @@ -73,6 +73,24 @@ static ctl_table mq_sysctls[] = {
> .extra1 = &msg_maxsize_limit_min,
> .extra2 = &msg_maxsize_limit_max,
> },
> + {
> + .procname = "msg_default",
> + .data = &init_ipc_ns.mq_msg_default,
> + .maxlen = sizeof(int),
> + .mode = 0644,
> + .proc_handler = proc_mq_dointvec_minmax,
> + .extra1 = &msg_max_limit_min,
> + .extra2 = &msg_max_limit_max,
> + },
> + {
> + .procname = "msgsize_default",
> + .data = &init_ipc_ns.mq_msgsize_default,
> + .maxlen = sizeof(int),
> + .mode = 0644,
> + .proc_handler = proc_mq_dointvec_minmax,
> + .extra1 = &msg_maxsize_limit_min,
> + .extra2 = &msg_maxsize_limit_max,
> + },
> {}
> };
>
> diff --git a/ipc/mqueue.c b/ipc/mqueue.c
> index 91ca145..f762fe6 100644
> --- a/ipc/mqueue.c
> +++ b/ipc/mqueue.c
> @@ -143,9 +143,10 @@ static struct inode *mqueue_get_inode(struct super_block *sb,
> info->qsize = 0;
> info->user = NULL; /* set when all is ok */
> memset(&info->attr, 0, sizeof(info->attr));
> - info->attr.mq_maxmsg = min(ipc_ns->mq_msg_max, DFLT_MSG);
> - info->attr.mq_msgsize =
> - min(ipc_ns->mq_msgsize_max, DFLT_MSGSIZE);
> + info->attr.mq_maxmsg = min(ipc_ns->mq_msg_max,
> + ipc_ns->mq_msg_default);
> + info->attr.mq_msgsize = min(ipc_ns->mq_msgsize_max,
> + ipc_ns->mq_msgsize_default);
> if (attr) {
> info->attr.mq_maxmsg = attr->mq_maxmsg;
> info->attr.mq_msgsize = attr->mq_msgsize;
> @@ -1262,6 +1263,8 @@ int mq_init_ns(struct ipc_namespace *ns)
> ns->mq_queues_max = DFLT_QUEUESMAX;
> ns->mq_msg_max = DFLT_MSGMAX;
> ns->mq_msgsize_max = DFLT_MSGSIZEMAX;
> + ns->mq_msg_default = DFLT_MSG;
> + ns->mq_msgsize_default = DFLT_MSGSIZE;
>
> ns->mq_mnt = kern_mount_data(&mqueue_fs_type, ns);
> if (IS_ERR(ns->mq_mnt)) {
> diff --git a/ipc/msgutil.c b/ipc/msgutil.c
> index 8b5ce5d3..a344216 100644
> --- a/ipc/msgutil.c
> +++ b/ipc/msgutil.c
> @@ -31,6 +31,8 @@ struct ipc_namespace init_ipc_ns = {
> .mq_queues_max = DFLT_QUEUESMAX,
> .mq_msg_max = DFLT_MSGMAX,
> .mq_msgsize_max = DFLT_MSGSIZEMAX,
> + .mq_msg_default = DFLT_MSG,
> + .mq_msgsize_default = DFLT_MSGSIZE,
> #endif
> .user_ns = &init_user_ns,
> };
> --
> 1.7.5.2
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