From 1e66413c4f68e2a61a210e4f5ff5df7a2ab86a5b Mon Sep 17 00:00:00 2001 From: Francesco Pollicino Date: Tue, 12 Mar 2019 09:59:33 +0100 Subject: block, bfq: print SHARED instead of pid for shared queues in logs MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The function "bfq_log_bfqq" prints the pid of the process associated with the queue passed as input. Unfortunately, if the queue is shared, then more than one process is associated with the queue. The pid that gets printed in this case is the pid of one of the associated processes. Which process gets printed depends on the exact sequence of merge events the queue underwent. So printing such a pid is rather useless and above all is often rather confusing because it reports a random pid between those of the associated processes. This commit addresses this issue by printing SHARED instead of a pid if the queue is shared. Tested-by: Holger Hoffstätte Tested-by: Oleksandr Natalenko Signed-off-by: Francesco Pollicino Signed-off-by: Paolo Valente Signed-off-by: Jens Axboe --- block/bfq-iosched.h | 23 +++++++++++++++++++---- 1 file changed, 19 insertions(+), 4 deletions(-) (limited to 'block/bfq-iosched.h') diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h index 829730b96fb2..67e63c276c7a 100644 --- a/block/bfq-iosched.h +++ b/block/bfq-iosched.h @@ -32,6 +32,8 @@ #define BFQ_DEFAULT_GRP_IOPRIO 0 #define BFQ_DEFAULT_GRP_CLASS IOPRIO_CLASS_BE +#define MAX_PID_STR_LENGTH 12 + /* * Soft real-time applications are extremely more latency sensitive * than interactive ones. Over-raise the weight of the former to @@ -1016,13 +1018,23 @@ void bfq_add_bfqq_busy(struct bfq_data *bfqd, struct bfq_queue *bfqq); /* --------------- end of interface of B-WF2Q+ ---------------- */ /* Logging facilities. */ +static inline void bfq_pid_to_str(int pid, char *str, int len) +{ + if (pid != -1) + snprintf(str, len, "%d", pid); + else + snprintf(str, len, "SHARED-"); +} + #ifdef CONFIG_BFQ_GROUP_IOSCHED struct bfq_group *bfqq_group(struct bfq_queue *bfqq); #define bfq_log_bfqq(bfqd, bfqq, fmt, args...) do { \ + char pid_str[MAX_PID_STR_LENGTH]; \ + bfq_pid_to_str((bfqq)->pid, pid_str, MAX_PID_STR_LENGTH); \ blk_add_cgroup_trace_msg((bfqd)->queue, \ bfqg_to_blkg(bfqq_group(bfqq))->blkcg, \ - "bfq%d%c " fmt, (bfqq)->pid, \ + "bfq%s%c " fmt, pid_str, \ bfq_bfqq_sync((bfqq)) ? 'S' : 'A', ##args); \ } while (0) @@ -1033,10 +1045,13 @@ struct bfq_group *bfqq_group(struct bfq_queue *bfqq); #else /* CONFIG_BFQ_GROUP_IOSCHED */ -#define bfq_log_bfqq(bfqd, bfqq, fmt, args...) \ - blk_add_trace_msg((bfqd)->queue, "bfq%d%c " fmt, (bfqq)->pid, \ +#define bfq_log_bfqq(bfqd, bfqq, fmt, args...) do { \ + char pid_str[MAX_PID_STR_LENGTH]; \ + bfq_pid_to_str((bfqq)->pid, pid_str, MAX_PID_STR_LENGTH); \ + blk_add_trace_msg((bfqd)->queue, "bfq%s%c " fmt, pid_str, \ bfq_bfqq_sync((bfqq)) ? 'S' : 'A', \ - ##args) + ##args); \ +} while (0) #define bfq_log_bfqg(bfqd, bfqg, fmt, args...) do {} while (0) #endif /* CONFIG_BFQ_GROUP_IOSCHED */ -- cgit