linux-kernel - Re: [tip:timers/core] [posix] 1535cb8028: stress-ng.epoll.ops_per

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CANn89i+nAN+p-qRypKxB4ESohXkKVPmHuV_m86j3DPv6_+C=oQ@mail.gmail.com>
Date: Thu, 27 Mar 2025 10:11:47 +0100
From: Eric Dumazet <edumazet@...gle.com>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: Mateusz Guzik <mjguzik@...il.com>, kernel test robot <oliver.sang@...el.com>, oe-lkp@...ts.linux.dev, 
	lkp@...el.com, linux-kernel@...r.kernel.org, x86@...nel.org, 
	Benjamin Segall <bsegall@...gle.com>, Frederic Weisbecker <frederic@...nel.org>
Subject: Re: [tip:timers/core] [posix] 1535cb8028: stress-ng.epoll.ops_per_sec
 36.2% regression

On Thu, Mar 27, 2025 at 9:26 AM Eric Dumazet <edumazet@...gle.com> wrote:

> We could place all these atomic fields in separate cache lines,
> to keep read-only fields shared as much as possible.
>

Following one-liner seems good enough to separate the 4 atomics used
to control/limit

UCOUNT_RLIMIT_NPROC, UCOUNT_RLIMIT_MSGQUEUE, UCOUNT_RLIMIT_SIGPENDING,
UCOUNT_RLIMIT_MEMLOCK,


diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index 7183e5aca282..6cc3fbec3632 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -120,7 +120,7 @@ struct ucounts {
        kuid_t uid;
        atomic_t count;
        atomic_long_t ucount[UCOUNT_COUNTS];
-       atomic_long_t rlimit[UCOUNT_RLIMIT_COUNTS];
+       atomic_long_t ____cacheline_aligned_in_smp rlimit[UCOUNT_RLIMIT_COUNTS];
 };

 extern struct user_namespace init_user_ns;