From mboxrd@z Thu Jan 1 00:00:00 1970 From: Balbir Singh Subject: Re: [RFC] [-mm PATCH] Memory controller fix swap charging context in unuse_pte() Date: Wed, 24 Oct 2007 17:44:42 +0530 Message-ID: <471F3732.5050407@linux.vnet.ibm.com> References: <20071005041406.21236.88707.sendpatchset@balbir-laptop> <4713A2F2.1010408@linux.vnet.ibm.com> Reply-To: balbir-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: 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: Hugh Dickins Cc: Linux Containers , Linux MM Mailing List List-Id: containers.vger.kernel.org Hugh Dickins wrote: > On Mon, 15 Oct 2007, Balbir Singh wrote: >> Hugh Dickins wrote: >>> --- 2.6.23-rc8-mm2/mm/swapfile.c 2007-09-27 12:03:36.000000000 +0100 >>> +++ linux/mm/swapfile.c 2007-10-07 14:33:05.000000000 +0100 >>> @@ -507,11 +507,23 @@ unsigned int count_swap_pages(int type, >>> * just let do_wp_page work it out if a write is requested later - to >>> * force COW, vm_page_prot omits write permission from any private vma. >>> */ >>> -static int unuse_pte(struct vm_area_struct *vma, pte_t *pte, >>> +static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd, >>> unsigned long addr, swp_entry_t entry, struct page *page) > ... >> I tested this patch and it seems to be working fine. I tried swapoff -a >> in the middle of tests consuming swap. Not 100% rigorous, but a good >> test nevertheless. >> >> Tested-by: Balbir Singh > > Thanks, Balbir. Sorry for the delay. I've not forgotten our > agreement that I should be splitting it into before-and-after > mem cgroup patches. But it's low priority for me until we're > genuinely assigning to a cgroup there. Hope to get back to > looking into that tomorrow, but no promises. > No Problem. We have some time with this one. > I think you still see no problem, where I claim that simply > omitting the mem charge mods from mm/swap_state.c leads to OOMs? > Maybe our difference is because my memhog in the cgroup is using > more memory than RAM, not just more memory than allowed to the > cgroup. I suspect that arrives at a state (when the swapcache > pages are not charged) where it cannot locate the pages it needs > to reclaim to stay within its limit. > Yes, in my case there I use memory less than RAM and more than that is allowed by the cgroup. It's quite possible that in your case the swapcache has grown significantly without any limit/control on it. The memhog program is using memory at a rate much higher than the rate of reclaim. Could you share your memhog program, please? In the use case you've mentioned/tested, having these mods to control swapcache is actually useful, right? Could you share your major objections at this point with the memory controller at this point. I hope to be able to look into/resolve them as my first priority in my list of items to work on. > Hugh -- Warm Regards, Balbir Singh Linux Technology Center IBM, ISTL