On Mon 29-02-16 09:27:44, Shi, Yang wrote:

On 2/29/2016 7:06 AM, Michal Hocko wrote:

quoted

On Fri 26-02-16 08:46:25, Yang Shi wrote:

quoted

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.
-- 
Michal Hocko
SUSE Labs

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>