linux-kernel - [PATCH v5 6/6] nvme: repack struct nvme_ns

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Date:   Fri,  8 Dec 2023 11:53:37 +0100
From:   Daniel Wagner <dwagner@...e.de>
To:     linux-nvme@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, Keith Busch <kbusch@...nel.org>,
        Christoph Hellwig <hch@....de>,
        Sagi Grimberg <sagi@...mberg.me>,
        Hannes Reinecke <hare@...e.de>, Daniel Wagner <dwagner@...e.de>
Subject: [PATCH v5 6/6] nvme: repack struct nvme_ns_head

ns_id, lba_shift and ms are always accessed for every read/write I/O in
nvme_setup_rw. By grouping these variables into one cacheline we can
safe some cycles.

4k sequential reads:

           baseline   patched
Bandwidth: 1620       1634
IOPs       66345579   66910939

Reviewed-by: Christoph Hellwig <hch@....de>
Signed-off-by: Daniel Wagner <dwagner@...e.de>
---
 drivers/nvme/host/nvme.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 8912292720d4..416794727364 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -445,21 +445,21 @@ struct nvme_ns_head {
 	struct list_head	list;
 	struct srcu_struct      srcu;
 	struct nvme_subsystem	*subsys;
-	unsigned		ns_id;
 	struct nvme_ns_ids	ids;
 	struct list_head	entry;
 	struct kref		ref;
 	bool			shared;
 	int			instance;
 	struct nvme_effects_log *effects;
+	u64			nuse;
+	unsigned		ns_id;
 	int			lba_shift;
 	u16			ms;
 	u16			pi_size;
-	u16			sgs;
-	u32			sws;
-	u64			nuse;
 	u8			pi_type;
 	u8			guard_type;
+	u16			sgs;
+	u32			sws;
 #ifdef CONFIG_BLK_DEV_ZONED
 	u64			zsze;
 #endif
-- 
2.43.0