From: Andrew Morton <akpm@linux-foundation.org> To: balbir@in.ibm.com Cc: vatsa@in.ibm.com, ckrm-tech@lists.sourceforge.net, xemul@sw.ru, linux-kernel@vger.kernel.org, linux-mm@kvack.org, menage@google.com, svaidy@linux.vnet.ibm.com, devel@openvz.org Subject: Re: [ckrm-tech] [RFC][PATCH][2/4] Add RSS accounting and control Date: Mon, 19 Feb 2007 03:01:41 -0800 [thread overview] Message-ID: <20070219030141.42c65bc0.akpm@linux-foundation.org> (raw) In-Reply-To: <45D97DF8.5080000@in.ibm.com> On Mon, 19 Feb 2007 16:07:44 +0530 Balbir Singh <balbir@in.ibm.com> wrote: > >> +void memctlr_mm_free(struct mm_struct *mm) > >> +{ > >> + kfree(mm->counter); > >> +} > >> + > >> +static inline void memctlr_mm_assign_container_direct(struct mm_struct *mm, > >> + struct container *cont) > >> +{ > >> + write_lock(&mm->container_lock); > >> + mm->container = cont; > >> + write_unlock(&mm->container_lock); > >> +} > > > > More weird locking here. > > > > The container field of the mm_struct is protected by a read write spin lock. That doesn't mean anything to me. What would go wrong if the above locking was simply removed? And how does the locking prevent that fault? > >> +void memctlr_mm_assign_container(struct mm_struct *mm, struct task_struct *p) > >> +{ > >> + struct container *cont = task_container(p, &memctlr_subsys); > >> + struct memctlr *mem = memctlr_from_cont(cont); > >> + > >> + BUG_ON(!mem); > >> + write_lock(&mm->container_lock); > >> + mm->container = cont; > >> + write_unlock(&mm->container_lock); > >> +} > > > > And here. > > Ditto. ditto ;) > > > >> +/* > >> + * Update the rss usage counters for the mm_struct and the container it belongs > >> + * to. We do not fail rss for pages shared during fork (see copy_one_pte()). > >> + */ > >> +int memctlr_update_rss(struct mm_struct *mm, int count, bool check) > >> +{ > >> + int ret = 1; > >> + struct container *cont; > >> + long usage, limit; > >> + struct memctlr *mem; > >> + > >> + read_lock(&mm->container_lock); > >> + cont = mm->container; > >> + read_unlock(&mm->container_lock); > >> + > >> + if (!cont) > >> + goto done; > > > > And here. I mean, if there was a reason for taking the lock around that > > read, then testing `cont' outside the lock just invalidated that reason. > > > > We took a consistent snapshot of cont. It cannot change outside the lock, > we check the value outside. I am sure I missed something. If it cannot change outside the lock then we don't need to take the lock! > > MEMCTLR_DONT_CHECK_LIMIT exists for the following reasons > > 1. Pages are shared during fork, fork() is not failed at that point > since the pages are shared anyway, we allow the RSS limit to be > exceeded. > 2. When ZERO_PAGE is added, we don't check for limits (zeromap_pte_range). > 3. On reducing RSS (passing -1 as the value) OK, that might make a nice comment somewhere (if it's not already there).
WARNING: multiple messages have this Message-ID (diff)
From: Andrew Morton <akpm@linux-foundation.org> To: balbir@in.ibm.com Cc: vatsa@in.ibm.com, ckrm-tech@lists.sourceforge.net, xemul@sw.ru, linux-kernel@vger.kernel.org, linux-mm@kvack.org, menage@google.com, svaidy@linux.vnet.ibm.com, devel@openvz.org Subject: Re: [ckrm-tech] [RFC][PATCH][2/4] Add RSS accounting and control Date: Mon, 19 Feb 2007 03:01:41 -0800 [thread overview] Message-ID: <20070219030141.42c65bc0.akpm@linux-foundation.org> (raw) In-Reply-To: <45D97DF8.5080000@in.ibm.com> On Mon, 19 Feb 2007 16:07:44 +0530 Balbir Singh <balbir@in.ibm.com> wrote: > >> +void memctlr_mm_free(struct mm_struct *mm) > >> +{ > >> + kfree(mm->counter); > >> +} > >> + > >> +static inline void memctlr_mm_assign_container_direct(struct mm_struct *mm, > >> + struct container *cont) > >> +{ > >> + write_lock(&mm->container_lock); > >> + mm->container = cont; > >> + write_unlock(&mm->container_lock); > >> +} > > > > More weird locking here. > > > > The container field of the mm_struct is protected by a read write spin lock. That doesn't mean anything to me. What would go wrong if the above locking was simply removed? And how does the locking prevent that fault? > >> +void memctlr_mm_assign_container(struct mm_struct *mm, struct task_struct *p) > >> +{ > >> + struct container *cont = task_container(p, &memctlr_subsys); > >> + struct memctlr *mem = memctlr_from_cont(cont); > >> + > >> + BUG_ON(!mem); > >> + write_lock(&mm->container_lock); > >> + mm->container = cont; > >> + write_unlock(&mm->container_lock); > >> +} > > > > And here. > > Ditto. ditto ;) > > > >> +/* > >> + * Update the rss usage counters for the mm_struct and the container it belongs > >> + * to. We do not fail rss for pages shared during fork (see copy_one_pte()). > >> + */ > >> +int memctlr_update_rss(struct mm_struct *mm, int count, bool check) > >> +{ > >> + int ret = 1; > >> + struct container *cont; > >> + long usage, limit; > >> + struct memctlr *mem; > >> + > >> + read_lock(&mm->container_lock); > >> + cont = mm->container; > >> + read_unlock(&mm->container_lock); > >> + > >> + if (!cont) > >> + goto done; > > > > And here. I mean, if there was a reason for taking the lock around that > > read, then testing `cont' outside the lock just invalidated that reason. > > > > We took a consistent snapshot of cont. It cannot change outside the lock, > we check the value outside. I am sure I missed something. If it cannot change outside the lock then we don't need to take the lock! > > MEMCTLR_DONT_CHECK_LIMIT exists for the following reasons > > 1. Pages are shared during fork, fork() is not failed at that point > since the pages are shared anyway, we allow the RSS limit to be > exceeded. > 2. When ZERO_PAGE is added, we don't check for limits (zeromap_pte_range). > 3. On reducing RSS (passing -1 as the value) OK, that might make a nice comment somewhere (if it's not already there). -- 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>
next prev parent reply other threads:[~2007-02-19 11:24 UTC|newest] Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top 2007-02-19 6:50 [RFC][PATCH][0/4] Memory controller (RSS Control) Balbir Singh 2007-02-19 6:50 ` Balbir Singh 2007-02-19 6:50 ` [RFC][PATCH][1/4] RSS controller setup Balbir Singh 2007-02-19 6:50 ` Balbir Singh 2007-02-19 8:57 ` Andrew Morton 2007-02-19 8:57 ` Andrew Morton 2007-02-19 9:18 ` Paul Menage 2007-02-19 9:18 ` Paul Menage 2007-02-19 11:13 ` Balbir Singh 2007-02-19 11:13 ` Balbir Singh 2007-02-19 19:43 ` Matthew Helsley 2007-02-19 19:43 ` Matthew Helsley 2007-02-19 10:06 ` Balbir Singh 2007-02-19 10:06 ` Balbir Singh 2007-02-19 6:50 ` [RFC][PATCH][2/4] Add RSS accounting and control Balbir Singh 2007-02-19 6:50 ` Balbir Singh 2007-02-19 8:58 ` Andrew Morton 2007-02-19 8:58 ` Andrew Morton 2007-02-19 10:37 ` [ckrm-tech] " Balbir Singh 2007-02-19 10:37 ` Balbir Singh 2007-02-19 11:01 ` Andrew Morton [this message] 2007-02-19 11:01 ` Andrew Morton 2007-02-19 11:09 ` Balbir Singh 2007-02-19 11:09 ` Balbir Singh 2007-02-19 11:23 ` Andrew Morton 2007-02-19 11:23 ` Andrew Morton 2007-02-19 11:56 ` Balbir Singh 2007-02-19 11:56 ` Balbir Singh 2007-02-19 12:09 ` Paul Menage 2007-02-19 12:09 ` Paul Menage 2007-02-19 14:10 ` Balbir Singh 2007-02-19 14:10 ` Balbir Singh 2007-02-19 16:07 ` Vaidyanathan Srinivasan 2007-02-19 16:07 ` Vaidyanathan Srinivasan 2007-02-19 16:17 ` Balbir Singh 2007-02-19 16:17 ` Balbir Singh 2007-02-20 6:40 ` Vaidyanathan Srinivasan 2007-02-20 6:40 ` Vaidyanathan Srinivasan 2007-02-19 6:50 ` [RFC][PATCH][3/4] Add reclaim support Balbir Singh 2007-02-19 6:50 ` Balbir Singh 2007-02-19 8:59 ` Andrew Morton 2007-02-19 8:59 ` Andrew Morton 2007-02-19 10:50 ` Balbir Singh 2007-02-19 10:50 ` Balbir Singh 2007-02-19 11:10 ` Andrew Morton 2007-02-19 11:10 ` Andrew Morton 2007-02-19 11:16 ` Balbir Singh 2007-02-19 11:16 ` Balbir Singh 2007-02-19 9:48 ` KAMEZAWA Hiroyuki 2007-02-19 9:48 ` KAMEZAWA Hiroyuki 2007-02-19 10:52 ` Balbir Singh 2007-02-19 10:52 ` Balbir Singh 2007-02-19 6:50 ` [RFC][PATCH][4/4] RSS controller documentation Balbir Singh 2007-02-19 6:50 ` Balbir Singh 2007-02-19 8:54 ` [RFC][PATCH][0/4] Memory controller (RSS Control) Andrew Morton 2007-02-19 8:54 ` Andrew Morton 2007-02-19 9:06 ` Paul Menage 2007-02-19 9:06 ` Paul Menage 2007-02-19 9:50 ` [ckrm-tech] " Kirill Korotaev 2007-02-19 9:50 ` Kirill Korotaev 2007-02-19 9:50 ` Paul Menage 2007-02-19 9:50 ` Paul Menage 2007-02-19 10:24 ` Balbir Singh 2007-02-19 10:24 ` Balbir Singh 2007-02-19 10:39 ` Balbir Singh 2007-02-19 10:39 ` Balbir Singh 2007-02-19 9:16 ` Magnus Damm 2007-02-19 9:16 ` Magnus Damm 2007-02-19 10:45 ` Balbir Singh 2007-02-19 10:45 ` Balbir Singh 2007-02-19 11:56 ` Magnus Damm 2007-02-19 11:56 ` Magnus Damm 2007-02-19 14:07 ` Balbir Singh 2007-02-19 14:07 ` Balbir Singh 2007-02-19 10:00 ` Balbir Singh 2007-02-19 10:00 ` Balbir Singh
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