On Mon 29-02-16 09:27:44, Shi, Yang wrote:
On 2/29/2016 7:06 AM, Michal Hocko wrote:
On Fri 26-02-16 08:46:25, Yang Shi wrote:
The list_lock was moved outside the for loop by commit e8dfc30582995ae12454cda517b17d6294175b07 ("writeback: elevate queue_io() into wb_writeback())", however, the commit log says "No behavior change", so it sounds safe to have the list_lock acquired inside the for loop as it did before. Leave tracepoints outside the critical area since tracepoints already have preempt disabled.
The patch says what but it completely misses the why part.
I'm just wondering the finer grained lock may reach a little better performance, i.e. more likely for preempt, lower latency.
If this is supposed to be a performance enhancement then some numbers would definitely make it easier to get in. Or even an arguments to back your theory. Basing your argument on 4+ years commit doesn't really seem sound... Just to make it clear, I am not opposing the patch I just stumbled over it and the changelog was just too terrible which made me response.