Re: [PATCH v6 0/8] Additional kmsg devices

Hello, Kazimierz.

On Wed, Feb 24, 2016 at 12:53:13PM +0100, Kazimierz Krosman wrote:

1. kmsg device does not require maintenance by reader process side.
Multiple writers can write to a device and new records overwrite logs saved earlier.
When system crashes logs can be restored with pstore mechanism.

I'm not sure this is the right layer to implement generic logging
facility.

2. Using kmsg can cause lower CPU utilisation in the real-word use case than 
userspace logging mechanisms.
We created 2 tests: (1) 100 writer processes write to created kmsg buffer and
(2) 100 writers write to socket (stream)- there is one reader to protect
socket buffer against overflow. Tests show that cpu utilisation in case of first
test is about 2.3 times lower (39.1%) than it is in second case (87.7%) (measured
with top program; tests code is attached below). Tested on Odroid XU4.

This sounds like a generic IPC problem than anything else.

Thanks.

-- 
tejun