diff options
| -rw-r--r-- | include/sys/zfs_debug.h | 18 |
1 files changed, 17 insertions, 1 deletions
diff --git a/include/sys/zfs_debug.h b/include/sys/zfs_debug.h index f60932b5a..7564ae0e4 100644 --- a/include/sys/zfs_debug.h +++ b/include/sys/zfs_debug.h @@ -20,7 +20,7 @@ */ /* * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved. - * Copyright (c) 2012, 2017 by Delphix. All rights reserved. + * Copyright (c) 2012, 2018 by Delphix. All rights reserved. */ #ifndef _SYS_ZFS_DEBUG_H @@ -58,6 +58,22 @@ extern int zfs_dbgmsg_enable; extern void __zfs_dbgmsg(char *buf); extern void __dprintf(boolean_t dprint, const char *file, const char *func, int line, const char *fmt, ...); + +/* + * Some general principles for using zfs_dbgmsg(): + * 1. We don't want to pollute the log with typically-irrelevant messages, + * so don't print too many messages in the "normal" code path - O(1) + * per txg. + * 2. We want to know for sure what happened, so make the message specific + * (e.g. *which* thing am I operating on). + * 3. Do print a message when something unusual or unexpected happens + * (e.g. error cases). + * 4. Print a message when making user-initiated on-disk changes. + * + * Note that besides principle 1, another reason that we don't want to + * use zfs_dbgmsg in high-frequency routines is the potential impact + * that it can have on performance. + */ #define zfs_dbgmsg(...) \ if (zfs_dbgmsg_enable) \ __dprintf(B_FALSE, __FILE__, __func__, __LINE__, __VA_ARGS__) |