On Tue, 8 Jun 2010 11:10:04 +0530 Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx> wrote: > * KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> [2010-06-08 12:19:01]: > > > Now, I think pre_destroy->force_empty() works very well and we can get rid of > > css_put/get per pages. This has very big effect in some special case. > > > > This is a test result with a multi-thread page fault program > > (I used at rwsem discussion.) > > > > [Before patch] > > 25.72% multi-fault-all [kernel.kallsyms] [k] clear_page_c > > 8.18% multi-fault-all [kernel.kallsyms] [k] try_get_mem_cgroup_from_mm > > 8.17% multi-fault-all [kernel.kallsyms] [k] down_read_trylock > > 8.03% multi-fault-all [kernel.kallsyms] [k] _raw_spin_lock_irqsave > > 5.46% multi-fault-all [kernel.kallsyms] [k] __css_put > > 5.45% multi-fault-all [kernel.kallsyms] [k] __alloc_pages_nodemask > > 4.36% multi-fault-all [kernel.kallsyms] [k] _raw_spin_lock_irq > > 4.35% multi-fault-all [kernel.kallsyms] [k] up_read > > 3.59% multi-fault-all [kernel.kallsyms] [k] css_put > > 2.37% multi-fault-all [kernel.kallsyms] [k] _raw_spin_lock > > 1.80% multi-fault-all [kernel.kallsyms] [k] mem_cgroup_add_lru_list > > 1.78% multi-fault-all [kernel.kallsyms] [k] __rmqueue > > 1.65% multi-fault-all [kernel.kallsyms] [k] handle_mm_fault > > > > try_get_mem_cgroup_from_mm() is a one of heavy ops because of false-sharing in > > css's counter for css_get/put. > > > > I removed that. > > > > [After] > > 26.16% multi-fault-all [kernel.kallsyms] [k] clear_page_c > > 11.73% multi-fault-all [kernel.kallsyms] [k] _raw_spin_lock > > 9.23% multi-fault-all [kernel.kallsyms] [k] _raw_spin_lock_irqsave > > 9.07% multi-fault-all [kernel.kallsyms] [k] down_read_trylock > > 6.09% multi-fault-all [kernel.kallsyms] [k] _raw_spin_lock_irq > > 5.57% multi-fault-all [kernel.kallsyms] [k] __alloc_pages_nodemask > > 4.86% multi-fault-all [kernel.kallsyms] [k] up_read > > 2.54% multi-fault-all [kernel.kallsyms] [k] __mem_cgroup_commit_charge > > 2.29% multi-fault-all [kernel.kallsyms] [k] _cond_resched > > 2.04% multi-fault-all [kernel.kallsyms] [k] mem_cgroup_add_lru_list > > 1.82% multi-fault-all [kernel.kallsyms] [k] handle_mm_fault > > > > Hmm. seems nice. But I don't convince my patch has no race. > > I'll continue test but your help is welcome. > > > > Looks nice, Kamezawa-San could you please confirm the source of > raw_spin_lock_irqsave and trylock from /proc/lock_stat? > Sure. But above result can be got when lockdep etc..are off. (it increase lock overhead) But yes, new _raw_spin_lock seems strange. > > == > > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> > > > > Now, memory cgroup increments css(cgroup subsys state)'s reference > > count per a charged page. And the reference count is kept until > > the page is uncharged. But this has 2 bad effect. > > > > 1. Because css_get/put calls atoimic_inc()/dec, heavy call of them > > on large smp will not scale well. > > 2. Because css's refcnt cannot be in a state as "ready-to-release", > > cgroup's notify_on_release handler can't work with memcg. > > > > This is a trial to remove css's refcnt per a page. Even if we remove > ^^ (per page) > > refcnt, pre_destroy() does enough synchronization. > > Could you also document what the rules for css_get/put now become? I > like the idea, but I am not sure if I understand the new rules > correctly by looking at the code. Hm. I'll try....but this just removes css_get/put per pages.. Thanks, -Kame -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>