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(cst-prg-14-82.cust.vodafone.cz. [46.135.14.82]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b76f4d533f2sm1753948866b.0.2025.12.03.02.01.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 03 Dec 2025 02:01:26 -0800 (PST) From: Mateusz Guzik To: kuniyu@google.com Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org, kuba@kernel.org, oliver.sang@intel.com, Mateusz Guzik Subject: [PATCH] af_unix: annotate unix_gc_lock with __cacheline_aligned_in_smp Date: Wed, 3 Dec 2025 11:01:22 +0100 Message-ID: <20251203100122.291550-1-mjguzik@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Otherwise the lock is susceptible to ever-changing false-sharing due to unrelated changes. This in particular popped up here where an unrelated change improved performance: https://lore.kernel.org/oe-lkp/202511281306.51105b46-lkp@intel.com/ Stabilize it with an explicit annotation which also has a side effect of furher improving scalability: > in our oiginal report, 284922f4c5 has a 6.1% performance improvement comp= aring > to parent 17d85f33a8. > we applied your patch directly upon 284922f4c5. as below, now by > "284922f4c5 + your patch" > we observe a 12.8% performance improvements (still comparing to 17d85f33a= 8). Note nothing was done for the other fields, so some fluctuation is still possible. Tested-by: kernel test robot Signed-off-by: Mateusz Guzik Reviewed-by: Kuniyuki Iwashima --- net/unix/garbage.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/unix/garbage.c b/net/unix/garbage.c index 78323d43e63e..25f65817faab 100644 --- a/net/unix/garbage.c +++ b/net/unix/garbage.c @@ -199,7 +199,7 @@ static void unix_free_vertices(struct scm_fp_list *fpl) } } =20 -static DEFINE_SPINLOCK(unix_gc_lock); +static __cacheline_aligned_in_smp DEFINE_SPINLOCK(unix_gc_lock); =20 void unix_add_edges(struct scm_fp_list *fpl, struct unix_sock *receiver) { --=20 2.48.1