Chunyan Zhang <zhang.lyra@xxxxxxxxx> wrote: > From: Prarit Bhargava <prarit@xxxxxxxxxx> > > printk.time=1/CONFIG_PRINTK_TIME=1 adds a unmodified local hardware clock > timestamp to printk messages. The local hardware clock loses time each > day making it difficult to determine exactly when an issue has occurred in > the kernel log, and making it difficult to determine how kernel and > hardware issues relate to each other in real time. > > Make printk output different timestamps by adding options for no > timestamp, the local hardware clock, the monotonic clock, the boottime > clock, and the real clock. Allow a user to pick one of the clocks by > using the printk.time kernel parameter. Output the type of clock in > /sys/module/printk/parameters/time so userspace programs can interpret the > timestamp. > > v13: This patch seems have being forgotten for 3 years. Rebase it on > the latest kernel v5.8, reolve conflicts and fix compiling errors. > Change code to adapt new printk_time usage. > Petr's concern on printk_time is addressed by current version of kernel, too. Lyra, Copying a reply I sent to Orson who sent me this patch privately this morning with some additional information. ISTR the reason that this was dropped was because of the a problem with the way systemd read the kernel's timestamps. It got the attention of Linus, and it was then pulled from the tree. I need to go back and review the entire thread as it's been several years since we had the discussion although ISTR someone mentioning that doing two timestamps would not be a problem for systemd. For example, [48551.015086] would be [48551.015086] m[xxxx.xxxx] for the monotonic clock timestamp, and [48551.015086] b[xxxx.xxxx] for the boottime clock, etc. P.
