[PATCH] Kill PF_SYNCWRITE flag
A process flag to indicate whether we are doing sync io is incredibly
ugly. It also causes performance problems when one does a lot of async
io and then proceeds to sync it. Part of the io will go out as async,
and the other part as sync. This causes a disconnect between the
previously submitted io and the synced io. For io schedulers such as CFQ,
this will cause us lost merges and suboptimal behaviour in scheduling.
Remove PF_SYNCWRITE completely from the fsync/msync paths, and let
the O_DIRECT path just directly indicate that the writes are sync
by using WRITE_SYNC instead.
Signed-off-by: Jens Axboe <axboe@suse.de>
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index c88f161d..4c4e9cc 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -277,8 +277,6 @@
static void cfq_dispatch_insert(request_queue_t *, struct cfq_rq *);
static struct cfq_queue *cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk, gfp_t gfp_mask);
-#define process_sync(tsk) ((tsk)->flags & PF_SYNCWRITE)
-
/*
* lots of deadline iosched dupes, can be abstracted later...
*/
@@ -334,7 +332,7 @@
static inline pid_t cfq_queue_pid(struct task_struct *task, int rw)
{
- if (rw == READ || process_sync(task))
+ if (rw == READ || rw == WRITE_SYNC)
return task->pid;
return CFQ_KEY_ASYNC;