Re: [PATCH] optimize dmapi event tests w/o dmapi config

[Eric Sandeen <sandeen@sandeen.net>]

Vlad Apostolov wrote:

> Eric Sandeen wrote:
>   
>> Defining XFS_DM_EVENT* macros to 0 in the absence of 
>> CONFIG_XFS_DMAPI allows gcc to optimize away tests that 
>> should never be true. Also wrap one hunk of xfs_unmount 
>> in #ifdef CONFIG_XFS_DMAPI
>>   
>>     
> Good idea Eric. A few remarks and a question below.
>   
>>  
>> +#ifdef CONFIG_XFS_DMAPI
>>   
>>     
> CONFIG_XFS_DMAPI is only defined when the DMAPI is statically linked
> to the kernel. When DMAPI is configured as a module,  
> CONFIG_XFS_DMAPI_MODULE
> is defined. The HAVE_DMAPI is defined for both, static and module DMAPI
> configurations.
>   
Hmm... ok.  kernel.org doesn't have that so you'll need to take care moving this 

patch to the kernel.org tree I guess.

>>  /* Defines for determining if an event message should be sent. */
>>  #define	DM_EVENT_ENABLED(vfsp, ip, event) ( \
>>  	unlikely ((vfsp)->vfs_flag & VFS_DMI) && \
>> @@ -78,6 +79,11 @@ typedef enum {
>>  		( ((io)->io_dmevmask & (1 << event)) || \
>>  		  ((io)->io_mount->m_dmevmask & (1 << event)) ) \
>>  	)
>> +#else
>> +#define DM_EVENT_ENABLED(vfsp, ip, event) (0)
>>   
>>     
> The above should use the new two arguments DM_EVENT_ENABLED macro.
>   
>> +#define DM_EVENT_ENABLED_IO(vfsp, io, event) (0)
>>   
>>     
> What is this DM_EVENT_ENABLE_IO macro for?
>   
Ah, this is just the differernce between kernel.org & CVS I guess.
I'm just re-defining existing macros in 2.6.22.1 to no-ops.

DM_EVENT_ENABLE_IO must have been removed from CVS w/o removing from
kernel.org (yet) - and I guess same goes for the argument count.

Anyway here's a CVS patch, sorry:

------

Defining XFS_DM_EVENT* macros to 0 in the absence of 
CONFIG_XFS_DMAPI allows gcc to optimize away tests that 
should never be true. Also wrap one hunk of xfs_unmount 
in #ifdef CONFIG_XFS_DMAPI

Stack deltas on x86, gcc 4.1:

xfs_create		-16
xfs_free_file_space	-4
xfs_getbmap		+4
xfs_link		-8
xfs_mkidr		-20
xfs_read		-24
xfs_remove		-12
xfs_rename		-8
xfs_rmdir		-16
xfs_setattr		-20
xfs_splice_read		-20
xfs_splice_write	-20
xfs_unmount		-48
xfs_write		-20

Signed-off-by: Eric Sandeen <sandeen@sandeen.net>

Index: linux.orig/fs/xfs/xfs_dmapi.h
===================================================================
--- linux.orig/fs/xfs/xfs_dmapi.h
+++ linux/fs/xfs/xfs_dmapi.h
@@ -67,11 +67,15 @@ typedef enum {
 #define HAVE_DM_RIGHT_T
 
 /* Defines for determining if an event message should be sent. */
+#ifdef HAVE_DMAPI
 #define	DM_EVENT_ENABLED(ip, event) ( \
 	unlikely (XFS_MTOVFS((ip)->i_mount)->vfs_flag & VFS_DMI) && \
 		( ((ip)->i_d.di_dmevmask & (1 << event)) || \
 		  ((ip)->i_mount->m_dmevmask & (1 << event)) ) \
 	)
+#else
+#define DM_EVENT_ENABLED(ip, event)	(0)
+#endif
 
 #define DM_XFS_VALID_FS_EVENTS		( \
 	(1 << DM_EVENT_PREUNMOUNT)	| \
Index: linux.orig/fs/xfs/xfs_vfsops.c
===================================================================
--- linux.orig/fs/xfs/xfs_vfsops.c
+++ linux/fs/xfs/xfs_vfsops.c
@@ -572,6 +572,7 @@ xfs_unmount(
 	rip = mp->m_rootip;
 	rvp = XFS_ITOV(rip);
 
+#ifdef HAVE_DMAPI
 	if (vfsp->vfs_flag & VFS_DMI) {
 		error = XFS_SEND_PREUNMOUNT(mp, vfsp,
 				rvp, DM_RIGHT_NULL, rvp, DM_RIGHT_NULL,
@@ -584,7 +585,7 @@ xfs_unmount(
 		unmount_event_flags = (mp->m_dmevmask & (1<<DM_EVENT_UNMOUNT))?
 					0 : DM_FLAGS_UNWANTED;
 	}
-
+#endif
 	/*
 	 * First blow any referenced inode from this file system
 	 * out of the reference cache, and delete the timer.