diff mbox series

[RESEND,v10,08/25] dept: Apply sdt_might_sleep_{start,end}() to PG_{locked,writeback} wait

Message ID 20230821034637.34630-9-byungchul@sk.com
State Not Applicable
Headers show
Series DEPT(Dependency Tracker) | expand

Commit Message

Byungchul Park Aug. 21, 2023, 3:46 a.m. UTC 
Makes Dept able to track dependencies by PG_{locked,writeback} waits.

Signed-off-by: Byungchul Park <byungchul@sk.com>
---
 mm/filemap.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

Comments

Matthew Wilcox Aug. 21, 2023, 4:09 a.m. UTC | #1 
On Mon, Aug 21, 2023 at 12:46:20PM +0900, Byungchul Park wrote:
> @@ -1219,6 +1220,9 @@ static inline bool folio_trylock_flag(struct folio *folio, int bit_nr,
>  /* How many times do we accept lock stealing from under a waiter? */
>  int sysctl_page_lock_unfairness = 5;
>  
> +static struct dept_map __maybe_unused PG_locked_map = DEPT_MAP_INITIALIZER(PG_locked_map, NULL);
> +static struct dept_map __maybe_unused PG_writeback_map = DEPT_MAP_INITIALIZER(PG_writeback_map, NULL);

Hmm, why are these "maybe unused"?  *digs*.  Ah.  Because
sdt_might_sleep_start() becomes a no-op macro if DEPT is disabled.

OK, the right way to handle this is

#ifdef CONFIG_DEPT
#define DEPT_MAP(name)	static struct dept_map name = \
		DEPT_MAP_INITIALIZER(name, NULL)
#else
#define DEPT_MAP(name)	/* */
#endif

And now DEPT takes up no space if disabled.

/* */; is a somewhat unusual thing to see, but since this must work at
top level, we can't use "do { } while (0)" like we usually do.  Given
where else this is likely to be used, i don't think it's going to be
a problem ...
Byungchul Park Aug. 21, 2023, 4:37 a.m. UTC | #2 
On Mon, Aug 21, 2023 at 05:09:44AM +0100, Matthew Wilcox wrote:
> On Mon, Aug 21, 2023 at 12:46:20PM +0900, Byungchul Park wrote:
> > @@ -1219,6 +1220,9 @@ static inline bool folio_trylock_flag(struct folio *folio, int bit_nr,
> >  /* How many times do we accept lock stealing from under a waiter? */
> >  int sysctl_page_lock_unfairness = 5;
> >  
> > +static struct dept_map __maybe_unused PG_locked_map = DEPT_MAP_INITIALIZER(PG_locked_map, NULL);
> > +static struct dept_map __maybe_unused PG_writeback_map = DEPT_MAP_INITIALIZER(PG_writeback_map, NULL);
> 
> Hmm, why are these "maybe unused"?  *digs*.  Ah.  Because
> sdt_might_sleep_start() becomes a no-op macro if DEPT is disabled.
> 
> OK, the right way to handle this is
> 
> #ifdef CONFIG_DEPT
> #define DEPT_MAP(name)	static struct dept_map name = \
> 		DEPT_MAP_INITIALIZER(name, NULL)
> #else
> #define DEPT_MAP(name)	/* */
> #endif
> 
> And now DEPT takes up no space if disabled.

Currently:

   #if !defined(CONFIG_DEPT)
   struct dept_map { }; 
   #endif

So I think it doesn't take space at all. Do you think I still need to
introduce e.g. DEPT_MAP()? Then I will. Thank you!

	Byungchul

> /* */; is a somewhat unusual thing to see, but since this must work at
> top level, we can't use "do { } while (0)" like we usually do.  Given
> where else this is likely to be used, i don't think it's going to be
> a problem ...
diff mbox series

Patch

diff --git a/mm/filemap.c b/mm/filemap.c
index 83dda76d1fc3..eed64dc88e43 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -44,6 +44,7 @@ 
 #include <linux/migrate.h>
 #include <linux/pipe_fs_i.h>
 #include <linux/splice.h>
+#include <linux/dept_sdt.h>
 #include <asm/pgalloc.h>
 #include <asm/tlbflush.h>
 #include "internal.h"
@@ -1219,6 +1220,9 @@  static inline bool folio_trylock_flag(struct folio *folio, int bit_nr,
 /* How many times do we accept lock stealing from under a waiter? */
 int sysctl_page_lock_unfairness = 5;
 
+static struct dept_map __maybe_unused PG_locked_map = DEPT_MAP_INITIALIZER(PG_locked_map, NULL);
+static struct dept_map __maybe_unused PG_writeback_map = DEPT_MAP_INITIALIZER(PG_writeback_map, NULL);
+
 static inline int folio_wait_bit_common(struct folio *folio, int bit_nr,
 		int state, enum behavior behavior)
 {
@@ -1230,6 +1234,11 @@  static inline int folio_wait_bit_common(struct folio *folio, int bit_nr,
 	unsigned long pflags;
 	bool in_thrashing;
 
+	if (bit_nr == PG_locked)
+		sdt_might_sleep_start(&PG_locked_map);
+	else if (bit_nr == PG_writeback)
+		sdt_might_sleep_start(&PG_writeback_map);
+
 	if (bit_nr == PG_locked &&
 	    !folio_test_uptodate(folio) && folio_test_workingset(folio)) {
 		delayacct_thrashing_start(&in_thrashing);
@@ -1331,6 +1340,8 @@  static inline int folio_wait_bit_common(struct folio *folio, int bit_nr,
 	 */
 	finish_wait(q, wait);
 
+	sdt_might_sleep_end();
+
 	if (thrashing) {
 		delayacct_thrashing_end(&in_thrashing);
 		psi_memstall_leave(&pflags);