ioq: introduce mog_ioq_contended hint

This will allow us to detect I/O contention on our queue
and yield the current thread to other clients for fairness.
This can prevent a client from hogging the thread in situations
where the network is much faster than the filesystem/disk.

1 files changed, 2 insertions, 0 deletions

diff --git a/cmogstored.h b/cmogstored.h
index f7fa022..4162931 100644
--- a/cmogstored.h
+++ b/cmogstored.h
@@ -101,6 +101,7 @@ struct mog_ioq {
         size_t max;
         pthread_mutex_t mtx;
         SIMPLEQ_HEAD(ioq_head, mog_fd) ioq_head;
+        bool contended;
         struct mog_svc *svc;
 };
 
@@ -635,6 +636,7 @@ void mog_yield(void);
 extern __thread struct mog_ioq *mog_ioq_current;
 void mog_ioq_init(struct mog_ioq *, struct mog_svc *, size_t val);
 bool mog_ioq_ready(struct mog_ioq *, struct mog_fd *) MOG_CHECK;
+bool mog_ioq_contended(void) MOG_CHECK;
 void mog_ioq_next(struct mog_ioq *);
 void mog_ioq_destroy(struct mog_ioq *);
 bool mog_ioq_unblock(struct mog_fd *);