Re: [PATCH V2] scsi: put hot fields of scsi_host_template into one cacheline

[Ming Lei <ming.lei@redhat.com>]

On Fri, May 01, 2020 at 06:27:07PM -0400, Douglas Gilbert wrote:
> On 2020-04-22 5:54 a.m., Ming Lei wrote:
> > The following three fields of scsi_host_template are referenced in
> > scsi IO submission path, so put them together into one cacheline:
> > 
> > - cmd_size
> > - queuecommand
> > - commit_rqs
> > 
> > Cc: Bart Van Assche <bvanassche@acm.org>
> > Cc: Christoph Hellwig <hch@lst.de>
> > Cc: John Garry <john.garry@huawei.com>
> > Signed-off-by: Ming Lei <ming.lei@redhat.com>
> > ---
> > V2:
> > 	- move the 3 fields at the beginning of scsi_host_template
> > 	- comment why we do this way
> > 
> >   include/scsi/scsi_host.h | 72 ++++++++++++++++++++++------------------
> >   1 file changed, 39 insertions(+), 33 deletions(-)
> 
> Hi,
> I would like to test this patch. However it doesn't apply on Martin's
> tree (all 3 chunks fail). Could you post a clean version?
> 
> Doug Gilbert
> 

Hi Doug,

Please try the following one:

From 356220ede9f06a20d90fa387cc84eb63eea2335d Mon Sep 17 00:00:00 2001
From: Ming Lei <ming.lei@redhat.com>
Date: Tue, 21 Apr 2020 17:27:30 +0800
Subject: [PATCH] scsi: put hot fields of scsi_host_template into one cacheline

The following three fields of scsi_host_template are referenced in
scsi IO submission path, so put them together into one cacheline:

- cmd_size
- queuecommand
- commit_rqs

Cc: Bart Van Assche <bvanassche@acm.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: John Garry <john.garry@huawei.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 include/scsi/scsi_host.h | 72 ++++++++++++++++++++++------------------
 1 file changed, 39 insertions(+), 33 deletions(-)

diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index 46ef8cccc982..6fa2697638b4 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -30,40 +30,15 @@ struct scsi_transport_template;
 #define MODE_TARGET 0x02
 
 struct scsi_host_template {
-	struct module *module;
-	const char *name;
-
 	/*
-	 * The info function will return whatever useful information the
-	 * developer sees fit.  If not provided, then the name field will
-	 * be used instead.
-	 *
-	 * Status: OPTIONAL
+	 * Put fields referenced in IO submission path together in
+	 * same cacheline
 	 */
-	const char *(* info)(struct Scsi_Host *);
 
 	/*
-	 * Ioctl interface
-	 *
-	 * Status: OPTIONAL
-	 */
-	int (*ioctl)(struct scsi_device *dev, unsigned int cmd,
-		     void __user *arg);
-
-
-#ifdef CONFIG_COMPAT
-	/* 
-	 * Compat handler. Handle 32bit ABI.
-	 * When unknown ioctl is passed return -ENOIOCTLCMD.
-	 *
-	 * Status: OPTIONAL
+	 * Additional per-command data allocated for the driver.
 	 */
-	int (*compat_ioctl)(struct scsi_device *dev, unsigned int cmd,
-			    void __user *arg);
-#endif
-
-	int (*init_cmd_priv)(struct Scsi_Host *shost, struct scsi_cmnd *cmd);
-	int (*exit_cmd_priv)(struct Scsi_Host *shost, struct scsi_cmnd *cmd);
+	unsigned int cmd_size;
 
 	/*
 	 * The queuecommand function is used to queue up a scsi
@@ -111,6 +86,41 @@ struct scsi_host_template {
 	 */
 	void (*commit_rqs)(struct Scsi_Host *, u16);
 
+	struct module *module;
+	const char *name;
+
+	/*
+	 * The info function will return whatever useful information the
+	 * developer sees fit.  If not provided, then the name field will
+	 * be used instead.
+	 *
+	 * Status: OPTIONAL
+	 */
+	const char *(*info)(struct Scsi_Host *);
+
+	/*
+	 * Ioctl interface
+	 *
+	 * Status: OPTIONAL
+	 */
+	int (*ioctl)(struct scsi_device *dev, unsigned int cmd,
+		     void __user *arg);
+
+
+#ifdef CONFIG_COMPAT
+	/*
+	 * Compat handler. Handle 32bit ABI.
+	 * When unknown ioctl is passed return -ENOIOCTLCMD.
+	 *
+	 * Status: OPTIONAL
+	 */
+	int (*compat_ioctl)(struct scsi_device *dev, unsigned int cmd,
+			    void __user *arg);
+#endif
+
+	int (*init_cmd_priv)(struct Scsi_Host *shost, struct scsi_cmnd *cmd);
+	int (*exit_cmd_priv)(struct Scsi_Host *shost, struct scsi_cmnd *cmd);
+
 	/*
 	 * This is an error handling strategy routine.  You don't need to
 	 * define one of these if you don't want to - there is a default
@@ -475,10 +485,6 @@ struct scsi_host_template {
 	 */
 	u64 vendor_id;
 
-	/*
-	 * Additional per-command data allocated for the driver.
-	 */
-	unsigned int cmd_size;
 	struct scsi_host_cmd_pool *cmd_pool;
 
 	/* Delay for runtime autosuspend */
-- 
2.25.2



-- 
Ming