From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vivek Goyal Subject: Re: [PATCH 1/2] memcg: dirty pages accounting and limiting infrastructure Date: Mon, 22 Feb 2010 13:07:32 -0500 Message-ID: <20100222180732.GC3096__12651.8909041353$1266862113$gmane$org@redhat.com> References: <1266765525-30890-1-git-send-email-arighi@develer.com> <1266765525-30890-2-git-send-email-arighi@develer.com> <20100221221700.GA5233@linux> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20100221221700.GA5233@linux> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Andrea Righi Cc: containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, David Rientjes , Suleiman Souhlal , Andrew Morton , Balbir Singh List-Id: containers.vger.kernel.org On Sun, Feb 21, 2010 at 11:17:01PM +0100, Andrea Righi wrote: > On Sun, Feb 21, 2010 at 01:28:35PM -0800, David Rientjes wrote: > > [snip] > > > > +static struct mem_cgroup *get_mem_cgroup_from_page(struct page *page) > > > +{ > > > + struct page_cgroup *pc; > > > + struct mem_cgroup *mem = NULL; > > > + > > > + pc = lookup_page_cgroup(page); > > > + if (unlikely(!pc)) > > > + return NULL; > > > + lock_page_cgroup(pc); > > > + if (PageCgroupUsed(pc)) { > > > + mem = pc->mem_cgroup; > > > + if (mem) > > > + css_get(&mem->css); > > > + } > > > + unlock_page_cgroup(pc); > > > + return mem; > > > +} > > > > Is it possible to merge this with try_get_mem_cgroup_from_page()? > > Agreed. > > > > > > + > > > +void mem_cgroup_charge_dirty(struct page *page, > > > + enum zone_stat_item idx, int charge) > > > +{ > > > + struct mem_cgroup *mem; > > > + struct mem_cgroup_stat_cpu *cpustat; > > > + unsigned long flags; > > > + int cpu; > > > + > > > + if (mem_cgroup_disabled()) > > > + return; > > > + /* Translate the zone_stat_item into a mem_cgroup_stat_index */ > > > + switch (idx) { > > > + case NR_FILE_DIRTY: > > > + idx = MEM_CGROUP_STAT_FILE_DIRTY; > > > + break; > > > + case NR_WRITEBACK: > > > + idx = MEM_CGROUP_STAT_WRITEBACK; > > > + break; > > > + case NR_WRITEBACK_TEMP: > > > + idx = MEM_CGROUP_STAT_WRITEBACK_TEMP; > > > + break; > > > + case NR_UNSTABLE_NFS: > > > + idx = MEM_CGROUP_STAT_UNSTABLE_NFS; > > > + break; > > > + default: > > > + return; > > > > WARN()? We don't want to silently leak counters. > > Agreed. > > > > > > + } > > > + /* Charge the memory cgroup statistics */ > > > + mem = get_mem_cgroup_from_page(page); > > > + if (!mem) { > > > + mem = root_mem_cgroup; > > > + css_get(&mem->css); > > > + } > > > > get_mem_cgroup_from_page() should probably handle the root_mem_cgroup case > > and return a reference from it. > > Right. But I'd prefer to use try_get_mem_cgroup_from_page() without > changing the behaviour of this function. > > > > > > + > > > + local_irq_save(flags); > > > + cpu = get_cpu(); > > > + cpustat = &mem->stat.cpustat[cpu]; > > > + __mem_cgroup_stat_add_safe(cpustat, idx, charge); > > > > get_cpu()? Preemption is already disabled, just use smp_processor_id(). > > mmmh... actually, we can just copy the code from > mem_cgroup_charge_statistics(), so local_irq_save/restore are not > necessarily needed and we can just use get_cpu()/put_cpu(). > > > > + put_cpu(); > > > + local_irq_restore(flags); > > > + css_put(&mem->css); > > > +} > > > + > > > static unsigned long mem_cgroup_get_local_zonestat(struct mem_cgroup *mem, > > > enum lru_list idx) > > > { > > > @@ -992,6 +1061,97 @@ static unsigned int get_swappiness(struct mem_cgroup *memcg) > > > return swappiness; > > > } > > > > > > +static unsigned long get_dirty_bytes(struct mem_cgroup *memcg) > > > +{ > > > + struct cgroup *cgrp = memcg->css.cgroup; > > > + unsigned long dirty_bytes; > > > + > > > + /* root ? */ > > > + if (cgrp->parent == NULL) > > > + return vm_dirty_bytes; > > > + > > > + spin_lock(&memcg->reclaim_param_lock); > > > + dirty_bytes = memcg->dirty_bytes; > > > + spin_unlock(&memcg->reclaim_param_lock); > > > + > > > + return dirty_bytes; > > > +} > > > + > > > +unsigned long mem_cgroup_dirty_bytes(void) > > > +{ > > > + struct mem_cgroup *memcg; > > > + unsigned long dirty_bytes; > > > + > > > + if (mem_cgroup_disabled()) > > > + return vm_dirty_bytes; > > > + > > > + rcu_read_lock(); > > > + memcg = mem_cgroup_from_task(current); > > > + if (memcg == NULL) > > > + dirty_bytes = vm_dirty_bytes; > > > + else > > > + dirty_bytes = get_dirty_bytes(memcg); > > > + rcu_read_unlock(); > > > > The rcu_read_lock() isn't protecting anything here. > > Right! Are we not protecting "memcg" pointer using rcu here? Thanks Vivek