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[144.49.247.118]) by smtp-relay.gmail.com with ESMTPS id 6a1803df08f44-8a596ff78c8sm2029486d6.23.2026.04.02.00.17.37 for (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Thu, 02 Apr 2026 00:17:37 -0700 (PDT) X-Relaying-Domain: broadcom.com X-CFilter-Loop: Reflected Received: by mail-pl1-f197.google.com with SMTP id d9443c01a7336-2b2471321dcso16580795ad.1 for ; Thu, 02 Apr 2026 00:17:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=broadcom.com; s=google; t=1775114256; x=1775719056; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=iANOw+j+FFixYv8CP4Q0aUKUIdpvufgAkkTBaFaBfMM=; b=f9qvXdtzvQVlY0SP5FBqiswyZ7ffWHFiAJNw0lKwK1NBVfmfgTR/LB+5jlwsZ5/oqP kaicCgBGDKcEjAiOQLsHz7nrHe+cFAjXhZaoKcpe8syaS4m3Y2VfD5fC2kTjX7u9ulB9 jNsPKk7mqkhB5WVRRZW9ZpFE2WK2nxiUUvde0= X-Forwarded-Encrypted: i=1; AJvYcCX9pRs9/GpLzufP8HeUeQOaQd3bL/eQN0HpElI+tplgM+wudX2Frgvw8ASFx+y6VDLZIE9wkrWqxeFQSg==@vger.kernel.org X-Received: by 2002:a17:903:1a2f:b0:2b2:4e5a:9471 with SMTP id d9443c01a7336-2b2758c365cmr20897085ad.22.1775114256632; Thu, 02 Apr 2026 00:17:36 -0700 (PDT) X-Received: by 2002:a17:903:1a2f:b0:2b2:4e5a:9471 with SMTP id d9443c01a7336-2b2758c365cmr20896855ad.22.1775114256232; Thu, 02 Apr 2026 00:17:36 -0700 (PDT) Received: from sumit_ws.dhcp.broadcom.net ([192.19.234.250]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2b27477c54bsm24612825ad.27.2026.04.02.00.17.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 02 Apr 2026 00:17:35 -0700 (PDT) From: Sumit Saxena To: martin.petersen@oracle.com, axboe@kernel.dk Cc: linux-scsi@vger.kernel.org, linux-block@vger.kernel.org, mpi3mr-linuxdrv.pdl@broadcom.com, James Rizzo , Sumit Saxena Subject: [PATCH 3/3] scsi: align scsi_device iodone_cnt to avoid cache line contention Date: Thu, 2 Apr 2026 13:16:37 +0530 Message-ID: <20260402074637.92417-4-sumit.saxena@broadcom.com> X-Mailer: git-send-email 2.43.7 In-Reply-To: <20260402074637.92417-1-sumit.saxena@broadcom.com> References: <20260402074637.92417-1-sumit.saxena@broadcom.com> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-DetectorID-Processed: b00c1d49-9d2e-4205-b15f-d015386d3d5e From: James Rizzo Place iodone_cnt on its own cache line so it does not share a cache line with iorequest_cnt, avoiding significant performance hits from false sharing when request and completion paths update these counters on some CPU architectures. Signed-off-by: James Rizzo Signed-off-by: Sumit Saxena --- include/scsi/scsi_device.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h index 9c2a7bbe5891..86c2a3a6b206 100644 --- a/include/scsi/scsi_device.h +++ b/include/scsi/scsi_device.h @@ -272,7 +272,9 @@ struct scsi_device { #define SCSI_DEFAULT_DEVICE_BLOCKED 3 atomic_t iorequest_cnt; - atomic_t iodone_cnt; + /* ensure iorequest_cnt and iodone_cnt are on different cache lines to avoid significant + performance hits on cache line contention on some CPU architectures */ + atomic_t iodone_cnt ____cacheline_aligned_in_smp; atomic_t ioerr_cnt; atomic_t iotmo_cnt; -- 2.43.7