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SubjectRe: [PATCH] ipc,mqueue: remove limits for the amount of system-wide queues
On Sun, 09 Feb 2014 13:06:03 -0800 Davidlohr Bueso <davidlohr@hp.com> wrote:

> From: Davidlohr Bueso <davidlohr@hp.com>
>
> Commit 93e6f119 (ipc/mqueue: cleanup definition names and locations) added
> global hardcoded limits to the amount of message queues that can be created.
> While these limits are per-namespace, reality is that it ends up breaking
> userspace applications. Historically users have, at least in theory, been able
> to create up to INT_MAX queues, and limiting it to just 1024 is way too low
> and dramatic for some workloads and use cases. For instance, Madars reports:
>
> "This update imposes bad limits on our multi-process application. As our
> app uses approaches that each process opens its own set of queues (usually
> something about 3-5 queues per process). In some scenarios we might run up
> to 3000 processes or more (which of-course for linux is not a problem).
> Thus we might need up to 9000 queues or more. All processes run under one
> user."
>
> Other affected users can be found in launchpad bug #1155695:
> https://bugs.launchpad.net/ubuntu/+source/manpages/+bug/1155695
>
> Instead of increasing this limit, revert it entirely and fallback to the
> original way of dealing queue limits -- where once a user's resource limit
> is reached, and all memory is used, new queues cannot be created.
>
> --- a/ipc/mq_sysctl.c
> +++ b/ipc/mq_sysctl.c
> @@ -22,6 +22,16 @@ static void *get_mq(ctl_table *table)
> return which;
> }
>
> +static int proc_mq_dointvec(ctl_table *table, int write,
> + void __user *buffer, size_t *lenp, loff_t *ppos)
> +{
> + struct ctl_table mq_table;
> + memcpy(&mq_table, table, sizeof(mq_table));
> + mq_table.data = get_mq(table);
> +
> + return proc_dointvec(&mq_table, write, buffer, lenp, ppos);
> +}
> +
> static int proc_mq_dointvec_minmax(ctl_table *table, int write,
> void __user *buffer, size_t *lenp, loff_t *ppos)
> {
>
> ...
>
> @@ -51,9 +59,7 @@ static ctl_table mq_sysctls[] = {
> .data = &init_ipc_ns.mq_queues_max,
> .maxlen = sizeof(int),
> .mode = 0644,
> - .proc_handler = proc_mq_dointvec_minmax,
> - .extra1 = &msg_queues_limit_min,
> - .extra2 = &msg_queues_limit_max,
> + .proc_handler = proc_mq_dointvec,
> },

hm, afaict proc_mq_dointvec() isn't needed - proc_dointvec_minmax()
will do the right thing if ->extra1 and/or ->extra2 are NULL, so we can
still use proc_mq_dointvec_minmax().

Which has absolutely nothing at all to do with your patch, but makes me
think we could take a sharp instrument to the sysctl code...


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