Re: [PATCH] ipc: optimize semget/shmget/msgget for lots of keys

From: Davidlohr Bueso <dave@stgolabs.net>
To: Guillaume Knispel <guillaume.knispel@supersonicimagine.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Manfred Spraul <manfred@colorfullife.com>,
	Kees Cook <keescook@chromium.org>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	"Peter Zijlstra (Intel)" <peterz@infradead.org>,
	Ingo Molnar <mingo@kernel.org>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Serge Hallyn <serge@hallyn.com>, Andrey Vagin <avagin@openvz.org>,
	Marc Pardo <marc.pardo@supersonicimagine.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] ipc: optimize semget/shmget/msgget for lots of keys
Date: Mon, 7 Aug 2017 11:21:03 -0700	[thread overview]
Message-ID: <20170807182103.GC25038@linux-80c1.suse> (raw)
In-Reply-To: <20170731084237.GA123231@ubuntu>

On Mon, 31 Jul 2017, Guillaume Knispel wrote:
> struct ipc_ids {
> 	int in_use;
> 	unsigned short seq;
>+	bool tables_initialized;

So this is really ugly to have, but I understand why you added it. I
wonder what folks would think if we just panic() in the rhashtable_init()
ENOMEM case, and convert the EINVALs to WARNs. This way the function
would always be called successfully. This is similar to what futex_init
does, with the underlying hash table allocator panicing. sems and msg
would probably have to be converted to pure_initcall, but hey, we could
at least get the symmetry back.

> static int __init ipc_ns_init(void)
> {
>-	shm_init_ns(&init_ipc_ns);
>-	return 0;
>+	const int err = shm_init_ns(&init_ipc_ns);
>+	WARN(err, "ipc: sysV shm_init_ns failed: %d\n", err);

nit: s/sysV/sysv

>+	return err;
> }

Thanks,
Davidlohr