On 6 November 2017 at 16:25, Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx> wrote: > On Mon, Nov 06, 2017 at 04:15:42PM +0100, Vincent Guittot wrote: >> Hi Pablo, >> >> On 6 November 2017 at 15:56, Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx> wrote: >> > On Mon, Nov 06, 2017 at 03:31:55PM +0100, Pablo Neira Ayuso wrote: >> >> On Thu, 2 Nov 2017 15:16:07 +0100 Vincent Guittot <vincent.guittot@xxxxxxxxxx> wrote: >> >> > conntrack uses the bounded system_long_wq workqueue for its works that >> >> > don't have to run on the cpu they have been queued. Using bounded >> >> > workqueue prevents the scheduler to make smart decision about the best >> >> > place to schedule the work. >> >> > >> >> > This patch replaces system_long_wq with system_power_efficient_wq. >> >> > the work stays bounded to a cpu by default unless the >> >> > CONFIG_WQ_POWER_EFFICIENT is enable. In the latter case, the work can >> >> > be scheduled on the best cpu from a power or a performance point of >> >> > view. >> >> >> >> Applied, thanks. >> > >> > I'm stepping back. According to what I'm reading >> > system_power_efficient_wq becomes system_wq when disabled, which is >> > not semantically the same as system_long_wq that we have now. >> >> When disabled, system_power_efficient_wq behaves like system_wq (and >> system_long_wq) as the worqueue are bounded to a cpu but It stays a >> different workqueue. >> >> > My concern is that the conntrack garbage collector may run for quite a >> > bit of time. Did you test this with a large conntrack table full of >> >> No, I haven't done specific tests with a large conntrack table full of entries. >> >> There is no system_power_efficient_long_wq. I was not convinced that >> we should create one that's why I have used system_power_efficient_wq > > My concern is that this garbage collector may run intensively on busy > conntrack tables to get rid of expired entries, so my question is if > switching from system_long_wq to system_wq is a real issue. system_long_wq and system_wq have the same configuration. They are just named differently so people will use one or the other but they behave exactly the same. Then system_power_efficient_wq is a 3rd workqueue that behaves like system_wq and system_long_wq when CONFIG_WQ_POWER_EFFICIENT is disable but uses ubounded workqueue when enabled I don't think that switching from system_long_wq to system_power_efficient_wq is an issue. I haven't seen any problem so far but i'm haven't done specific tests that stress the system with a large conntrack table full of entries. Furthermore, these workqueue use default max active context (256) which means that other work should be able to run. Regards, Vincent > > Thanks. -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
