kernel: reuse a single allocation for all vfs_requests of a process

$ iostress 32 512 0 > /vtty # before
512 calls, 0 bytes. avg 121133
$ iostress 32 512 0 > /vtty # after
512 calls, 0 bytes. avg 103540

103540/121133 = ~85%

I think the tiny bit of added complexity is worth it here.

1 files changed, 3 insertions, 3 deletions

diff --git a/src/kernel/proc.h b/src/kernel/proc.h
index c7e885a..d6f84bd 100644
--- a/src/kernel/proc.h
+++ b/src/kernel/proc.h
@@ -36,9 +36,6 @@ struct process {
 	union {
 		int death_msg; // PS_DEAD
 		struct {
-			struct vfs_request *req;
-		} waits4fs; // PS_WAITS4FS
-		struct {
 			char __user *buf;
 			size_t max_len;
 			struct fs_wait_response __user *res;
@@ -52,6 +49,9 @@ struct process {
 	};
 	struct vfs_request *handled_req;
 
+	/* allocated once, the requests from WAITS4FS get stored here */
+	struct vfs_request *reqslot;
+
 	/* vfs_backend controlled (not exclusively) by this process */
 	struct vfs_backend *controlled;