Received-SPF: pass (google.com: domain of linux-kernel+bounces-180733-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:40f1:3f00::1 as permitted sender) client-ip=2604:1380:40f1:3f00::1;
From: Yang Yang <yang.yang@vivo.com>
To: Alasdair Kergon <agk@redhat.com>,
	Mike Snitzer <snitzer@kernel.org>,
	Mikulas Patocka <mpatocka@redhat.com>,
	dm-devel@lists.linux.dev,
	linux-kernel@vger.kernel.org
Cc: Yang Yang <yang.yang@vivo.com>
Subject: [PATCH v4 4/5] dm: Avoid sending redundant empty flush bios to the same block device
Date: Thu, 16 May 2024 16:03:17 +0800
Message-Id: <20240516080318.120231-5-yang.yang@vivo.com>
In-Reply-To: <20240516080318.120231-1-yang.yang@vivo.com>
References: <20240516080318.120231-1-yang.yang@vivo.com>
Content-Transfer-Encoding: 8bit
Content-Type: text/plain
Precedence: bulk
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0:
	=?us-ascii?Q?KI/mL0AeTwWoy0nDbkTVNimcTYlcZCzqAHb/hZcR9/elYENcp5tWyBsGDKfr?=
 =?us-ascii?Q?Hk/ke9z9eqoVCuFh6lyXu9HIplzjYUR5djQO4/PkaKK9XTUd4uKqVf5D/hGA?=
 =?us-ascii?Q?xdy6flGJ7+CfJElNZ5X3VtMTwcz8GXPfpwwXKe+9+u3dsnTHWj5VPbn0/Y+u?=
 =?us-ascii?Q?Dd1LyxJMHQSWifpiG6k7ypG16BNxGV1V293ICLg28ETO73iFHmTin25b1tUa?=
 =?us-ascii?Q?gWBvjkWv8YTa5jyiC6UEVqiu2VujB1WsfpEmMi+ne8OGMw51nHkM3BJ3tUha?=
 =?us-ascii?Q?AJsVdhFZ96EnobwKA5rEq3MkysZlQeZsnIbWwaALaNUYlUAWbvtLNgUo8wDr?=
 =?us-ascii?Q?/xWbvrZdudGCSj6X07hCULhowzV75JMFz/H2xWrOO0kYr5+Qpp1OGmuJMdgs?=
 =?us-ascii?Q?fCV2GKatKng8KQKwA7DImaNW5XPJ+vbq7c1tjubITLO/P5w3nwyXnZ4oDnmr?=
 =?us-ascii?Q?AEkZh51uaPNjXLl7aOStN+YJXkK8ZDfJK09c4uCw5MrcxY4MYoDS+u7diwgG?=
 =?us-ascii?Q?QDXJrBYdp1Sn23xV0FYCSwLTsSDmvTAg6EvsVgN3/dUMgGrtlkN1eKxG/8+9?=
 =?us-ascii?Q?TAUlULawbGmo5DXNkzUHN+kwsU4U7Gtpi2dMXFq0XENPHhZlM8QxzyqvnIok?=
 =?us-ascii?Q?+Omd/91frxctBoSqZvP0Kzeuxvo5jnDPfVIGHen/LFR867NKBf1V0H/lwIzQ?=
 =?us-ascii?Q?7Xdy7f0kOTXdrX/lyh8pLkBmKgMi1cVEJl7qaXfKgjEgEwMR2IPe2ovyeOm+?=
 =?us-ascii?Q?Au4wse9vaUJBOCAK7FZOEm7batqbi2pnsma4gJzZSUz0CUTi+CM9XYra1nGC?=
 =?us-ascii?Q?3xDYdzZu5c0Hi9X+BWOqXiTsUAiXBv5UCVSyxPnDW+LGoKovGd2Vz0124LJc?=
 =?us-ascii?Q?V7uh+QHUgtddQB+Kj5X2U/qTSrHBVfNuL1MYLpnnZnl4ezmtx5XZy+0zvAiA?=
 =?us-ascii?Q?XTAH/q3UXG8beWuqS4aCMNJ9rcr2WGmcbiDeESGKSAml2sr8NULI3Jydjki6?=
 =?us-ascii?Q?WEsNWpQa2SmpqClzWJqesNOIjzprjT0f+br0OrNDjIbx5q56LPzsGfhXPKOO?=
 =?us-ascii?Q?hf4mANZGkEZlWSwvuY0MG+vei/QrzcKPy3kE7q5ISLT+yJpct47/AMB09+4f?=
 =?us-ascii?Q?KmNZqhjvV1LsS/BKk7KWAlqOJGanD+DoM6kNfnDwqraKltpYTc7wTncAxRKG?=
 =?us-ascii?Q?bDGZx23agfOL+l/TleVgNmZn/oWouWWZizwVCHrAL+NQwZte+sDOyogzVG6d?=
 =?us-ascii?Q?H8/xlF2cQyAqNy/werJy+ppKW7gj0TpWcufkrBoSHv5A88wb7Eu0aIMT/oUt?=
 =?us-ascii?Q?UAs2GAIjEXctzj78HYRIcm/s3Ai1O/LNdX5fKU9e2PG4dHy5Ti6Cud/L5wby?=
 =?us-ascii?Q?UgJp1OZKr81ekMRjimJ0l4gClFOHEHCRgHb5yDx0ACMdNQhyuSZxoLKyc4Gf?=
 =?us-ascii?Q?KRH4jyrQlp4q+FDUB1hPPOJHZvHYEFlft7W9sxKhHkVyaJ3X0Qn48ybj0Wzu?=
 =?us-ascii?Q?VgCp7adsC5BZWnBBnS9TOhSrM98nIpsi0wNBcyM0lUeZalU+Cpe96aGRHAGb?=
 =?us-ascii?Q?PH7qMMtqT63K27IpgA4v30WqdyET4hCDD52hPmdb?=
X-OriginatorOrg: vivo.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 6ed83c32-e6bf-4f77-8611-08dc757ec67e
X-MS-Exchange-CrossTenant-AuthSource: TYSPR06MB6411.apcprd06.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 16 May 2024 08:04:13.7946
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 923e42dc-48d5-4cbe-b582-1a797a6412ed
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: BeI8ubqFgMmQgk3sx0uObkAM5DLSuUeWSr6zRd/matPnYRh57OfKCW54NCLxsb3d9I21+5M3wyMqmrwsEi0X+A==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: SEYPR06MB6830

If the num_targets is greater than the number of dm_devs in the
dm_table's devices list, __send_empty_flush() might invoke
__send_duplicate_bios() multiple times for the same block device.
This could lead to a substantial decrease in performance when
num_targets significantly exceeds the number of dm_devs.
This patch ensure that __send_duplicate_bios() is only called once
for each dm_dev.

Signed-off-by: Yang Yang <yang.yang@vivo.com>
---
 drivers/md/dm.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 25215b93c3cf..9dd0f5c97028 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1561,6 +1561,7 @@ static void __send_empty_flush(struct clone_info *ci)
 {
 	struct dm_table *t = ci->map;
 	struct bio flush_bio;
+	struct dm_dev_internal *dd;
 
 	/*
 	 * Use an on-stack bio for this, it's safe since we don't
@@ -1574,10 +1575,18 @@ static void __send_empty_flush(struct clone_info *ci)
 	ci->sector_count = 0;
 	ci->io->tio.clone.bi_iter.bi_size = 0;
 
-	for (unsigned int i = 0; i < t->num_targets; i++) {
-		struct dm_target *ti = dm_table_get_target(t, i);
+	if (!t->flush_pass_around) {
+		for (unsigned int i = 0; i < t->num_targets; i++) {
+			struct dm_target *ti = dm_table_get_target(t, i);
+			__send_empty_flush_bios(t, ti, ci);
+		}
+	} else {
+		down_read(&t->devices_lock);
+
+		list_for_each_entry(dd, dm_table_get_devices(t), list)
+			__send_empty_flush_bios(t, dd->dm_dev->ti, ci);
 
-		__send_empty_flush_bios(t, ti, ci);
+		up_read(&t->devices_lock);
 	}
 
 	/*
-- 
2.34.1