From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A9BB81DE4C2; Thu, 17 Jul 2025 05:27:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752730024; cv=none; b=tnlEnQdOM925rw0a7tBi5STlmdZttY4fk1sjRL7QPRNuoVCyznl4/nchj1L2EuWZTwKR/TCqh6OY2OxWgh6OuLunVK/voSIaxidGtQqhzQt8ljyhHveXkWLnqq4VX2Nx/DSouGRMaLovReUW213aWM5CgEwUcuO9+z9bxiWt6ds= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752730024; c=relaxed/simple; bh=WHynN3RVdKyk3zkts6sRyj9KOWiQ90DdnEukQI8ear4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=RSqEOcIS810HRYCyrwSyrVoTMF97myYIXjNw3FI90ksHbFcdXhTFeRxnam3JWb+ZWp1GGU88gQCHvRpyZhtekLJmEIGrRHS9iB6/AgAjXeX16fmYr4lOOFEEgxDM7MkSCU26GoDX2Y4DYAZSGcUduIq91uQXVcNvIS0NgP1MrS8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=bCOLYyYz; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="bCOLYyYz" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B810FC4CEE3; Thu, 17 Jul 2025 05:27:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1752730024; bh=WHynN3RVdKyk3zkts6sRyj9KOWiQ90DdnEukQI8ear4=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=bCOLYyYzJ0BI5iXBrUIPsBz6zEdv1MW1P2boc7rYfEQl8Kq1mXZnPbvQq9E95QXth iZFCHycWLEA2ptKmdmjXc+eZwLJMjgy+BrDBdCtxbzXMTF6sHzYn+U8CW3URT+kBoq 4M4HB+JjOdr7VTyvTjowTEM1Gb7UkiVE15DsQ2H2geR1+Vr8TqVHRclIUBEbqdQGVl DzNFfgGGePJe8MjqXjN69fDanp+Ebywa4ByfCalpPXVc5xH2tgPJDeRyBh1peqyaw1 6gC9H76ha42V4ztBIepF/6IePHMcfTxOl80DKR8xxY0q+SyV7awljmiDryFAnrk3MH zGEpdv1UQkYCA== Message-ID: <48e6e92d-6b6a-4850-9396-f3afa327ca3a@kernel.org> Date: Thu, 17 Jul 2025 07:26:59 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] kernel/fork: Increase minimum number of allowed threads To: Hauke Mehrtens , sashal@kernel.org, linux-kernel@vger.kernel.org Cc: frederic@kernel.org, david@redhat.com, viro@zeniv.linux.org.uk, paulmck@kernel.org, stable@vger.kernel.org, David Laight , Tejun Heo , Lai Jiangshan , "Luis R . Rodriguez" References: <20250711230829.214773-1-hauke@hauke-m.de> Content-Language: en-US From: Jiri Slaby Autocrypt: addr=jirislaby@kernel.org; keydata= xsFNBE6S54YBEACzzjLwDUbU5elY4GTg/NdotjA0jyyJtYI86wdKraekbNE0bC4zV+ryvH4j rrcDwGs6tFVrAHvdHeIdI07s1iIx5R/ndcHwt4fvI8CL5PzPmn5J+h0WERR5rFprRh6axhOk rSD5CwQl19fm4AJCS6A9GJtOoiLpWn2/IbogPc71jQVrupZYYx51rAaHZ0D2KYK/uhfc6neJ i0WqPlbtIlIrpvWxckucNu6ZwXjFY0f3qIRg3Vqh5QxPkojGsq9tXVFVLEkSVz6FoqCHrUTx wr+aw6qqQVgvT/McQtsI0S66uIkQjzPUrgAEtWUv76rM4ekqL9stHyvTGw0Fjsualwb0Gwdx ReTZzMgheAyoy/umIOKrSEpWouVoBt5FFSZUyjuDdlPPYyPav+hpI6ggmCTld3u2hyiHji2H cDpcLM2LMhlHBipu80s9anNeZhCANDhbC5E+NZmuwgzHBcan8WC7xsPXPaiZSIm7TKaVoOcL 9tE5aN3jQmIlrT7ZUX52Ff/hSdx/JKDP3YMNtt4B0cH6ejIjtqTd+Ge8sSttsnNM0CQUkXps w98jwz+Lxw/bKMr3NSnnFpUZaxwji3BC9vYyxKMAwNelBCHEgS/OAa3EJoTfuYOK6wT6nadm YqYjwYbZE5V/SwzMbpWu7Jwlvuwyfo5mh7w5iMfnZE+vHFwp/wARAQABzSFKaXJpIFNsYWJ5 IDxqaXJpc2xhYnlAa2VybmVsLm9yZz7CwXcEEwEIACEFAlW3RUwCGwMFCwkIBwIGFQgJCgsC BBYCAwECHgECF4AACgkQvSWxBAa0cEnVTg//TQpdIAr8Tn0VAeUjdVIH9XCFw+cPSU+zMSCH eCZoA/N6gitEcnvHoFVVM7b3hK2HgoFUNbmYC0RdcSc80pOF5gCnACSP9XWHGWzeKCARRcQR 4s5YD8I4VV5hqXcKo2DFAtIOVbHDW+0okOzcecdasCakUTr7s2fXz97uuoc2gIBB7bmHUGAH XQXHvdnCLjDjR+eJN+zrtbqZKYSfj89s/ZHn5Slug6w8qOPT1sVNGG+eWPlc5s7XYhT9z66E l5C0rG35JE4PhC+tl7BaE5IwjJlBMHf/cMJxNHAYoQ1hWQCKOfMDQ6bsEr++kGUCbHkrEFwD UVA72iLnnnlZCMevwE4hc0zVhseWhPc/KMYObU1sDGqaCesRLkE3tiE7X2cikmj/qH0CoMWe gjnwnQ2qVJcaPSzJ4QITvchEQ+tbuVAyvn9H+9MkdT7b7b2OaqYsUP8rn/2k1Td5zknUz7iF oJ0Z9wPTl6tDfF8phaMIPISYrhceVOIoL+rWfaikhBulZTIT5ihieY9nQOw6vhOfWkYvv0Dl o4GRnb2ybPQpfEs7WtetOsUgiUbfljTgILFw3CsPW8JESOGQc0Pv8ieznIighqPPFz9g+zSu Ss/rpcsqag5n9rQp/H3WW5zKUpeYcKGaPDp/vSUovMcjp8USIhzBBrmI7UWAtuedG9prjqfO wU0ETpLnhgEQAM+cDWLL+Wvc9cLhA2OXZ/gMmu7NbYKjfth1UyOuBd5emIO+d4RfFM02XFTI t4MxwhAryhsKQQcA4iQNldkbyeviYrPKWjLTjRXT5cD2lpWzr+Jx7mX7InV5JOz1Qq+P+nJW YIBjUKhI03ux89p58CYil24Zpyn2F5cX7U+inY8lJIBwLPBnc9Z0An/DVnUOD+0wIcYVnZAK DiIXODkGqTg3fhZwbbi+KAhtHPFM2fGw2VTUf62IHzV+eBSnamzPOBc1XsJYKRo3FHNeLuS8 f4wUe7bWb9O66PPFK/RkeqNX6akkFBf9VfrZ1rTEKAyJ2uqf1EI1olYnENk4+00IBa+BavGQ 8UW9dGW3nbPrfuOV5UUvbnsSQwj67pSdrBQqilr5N/5H9z7VCDQ0dhuJNtvDSlTf2iUFBqgk 3smln31PUYiVPrMP0V4ja0i9qtO/TB01rTfTyXTRtqz53qO5dGsYiliJO5aUmh8swVpotgK4 /57h3zGsaXO9PGgnnAdqeKVITaFTLY1ISg+Ptb4KoliiOjrBMmQUSJVtkUXMrCMCeuPDGHo7 39Xc75lcHlGuM3yEB//htKjyprbLeLf1y4xPyTeeF5zg/0ztRZNKZicgEmxyUNBHHnBKHQxz 1j+mzH0HjZZtXjGu2KLJ18G07q0fpz2ZPk2D53Ww39VNI/J9ABEBAAHCwV8EGAECAAkFAk6S 54YCGwwACgkQvSWxBAa0cEk3tRAAgO+DFpbyIa4RlnfpcW17AfnpZi9VR5+zr496n2jH/1ld wRO/S+QNSA8qdABqMb9WI4BNaoANgcg0AS429Mq0taaWKkAjkkGAT7mD1Q5PiLr06Y/+Kzdr 90eUVneqM2TUQQbK+Kh7JwmGVrRGNqQrDk+gRNvKnGwFNeTkTKtJ0P8jYd7P1gZb9Fwj9YLx jhn/sVIhNmEBLBoI7PL+9fbILqJPHgAwW35rpnq4f/EYTykbk1sa13Tav6btJ+4QOgbcezWI wZ5w/JVfEJW9JXp3BFAVzRQ5nVrrLDAJZ8Y5ioWcm99JtSIIxXxt9FJaGc1Bgsi5K/+dyTKL wLMJgiBzbVx8G+fCJJ9YtlNOPWhbKPlrQ8+AY52Aagi9WNhe6XfJdh5g6ptiOILm330mkR4g W6nEgZVyIyTq3ekOuruftWL99qpP5zi+eNrMmLRQx9iecDNgFr342R9bTDlb1TLuRb+/tJ98 f/bIWIr0cqQmqQ33FgRhrG1+Xml6UXyJ2jExmlO8JljuOGeXYh6ZkIEyzqzffzBLXZCujlYQ DFXpyMNVJ2ZwPmX2mWEoYuaBU0JN7wM+/zWgOf2zRwhEuD3A2cO2PxoiIfyUEfB9SSmffaK/ S4xXoB6wvGENZ85Hg37C7WDNdaAt6Xh2uQIly5grkgvWppkNy4ZHxE+jeNsU7tg= In-Reply-To: <20250711230829.214773-1-hauke@hauke-m.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc wqueue & umode helper folks On 12. 07. 25, 1:08, Hauke Mehrtens wrote: > A modern Linux system creates much more than 20 threads at bootup. > When I booted up OpenWrt in qemu the system sometimes failed to boot up > when it wanted to create the 419th thread. The VM had 128MB RAM and the > calculation in set_max_threads() calculated that max_threads should be > set to 419. When the system booted up it tried to notify the user space > about every device it created because CONFIG_UEVENT_HELPER was set and > used. I counted 1299 calls to call_usermodehelper_setup(), all of > them try to create a new thread and call the userspace hotplug script in > it. > > This fixes bootup of Linux on systems with low memory. > > I saw the problem with qemu 10.0.2 using these commands: > qemu-system-aarch64 -machine virt -cpu cortex-a57 -nographic > > Cc: stable@vger.kernel.org > Signed-off-by: Hauke Mehrtens > --- > kernel/fork.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/fork.c b/kernel/fork.c > index 7966c9a1c163..388299525f3c 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -115,7 +115,7 @@ > /* > * Minimum number of threads to boot the kernel > */ > -#define MIN_THREADS 20 > +#define MIN_THREADS 600 As David noted, this is not the proper fix. It appears that usermode helper should use limited thread pool. I.e. instead of system_unbound_wq, alloc_workqueue("", WQ_UNBOUND, max_active) with max_active set to max_threads divided by some arbitrary constant (3? 4?)? regards, -- js suse labs