From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it0-f71.google.com (mail-it0-f71.google.com [209.85.214.71]) by kanga.kvack.org (Postfix) with ESMTP id 8F6CD6B0069 for ; Wed, 14 Sep 2016 05:35:28 -0400 (EDT) Received: by mail-it0-f71.google.com with SMTP id 186so38883284itf.2 for ; Wed, 14 Sep 2016 02:35:28 -0700 (PDT) Received: from szxga03-in.huawei.com (szxga03-in.huawei.com. [119.145.14.66]) by mx.google.com with ESMTP id x78si7457470oia.164.2016.09.14.02.35.15 for ; Wed, 14 Sep 2016 02:35:16 -0700 (PDT) Message-ID: <57D91771.9050108@huawei.com> Date: Wed, 14 Sep 2016 17:25:05 +0800 From: zhong jiang MIME-Version: 1.0 Subject: Re: [PATCH] mm: fix oom work when memory is under pressure References: <1473173226-25463-1-git-send-email-zhongjiang@huawei.com> <20160909114410.GG4844@dhcp22.suse.cz> <57D67A8A.7070500@huawei.com> <20160912111327.GG14524@dhcp22.suse.cz> <57D6B0C4.6040400@huawei.com> <20160912174445.GC14997@dhcp22.suse.cz> <57D7FB71.9090102@huawei.com> <20160913132854.GB6592@dhcp22.suse.cz> <57D8F8AE.1090404@huawei.com> <20160914084219.GA1612@dhcp22.suse.cz> <20160914085227.GB1612@dhcp22.suse.cz> In-Reply-To: <20160914085227.GB1612@dhcp22.suse.cz> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: akpm@linux-foundation.org, vbabka@suse.cz, rientjes@google.com, linux-mm@kvack.org, Xishi Qiu , Hanjun Guo , Hugh Dickins On 2016/9/14 16:52, Michal Hocko wrote: > On Wed 14-09-16 10:42:19, Michal Hocko wrote: >> [Let's CC Hugh] > now for real... > >> On Wed 14-09-16 15:13:50, zhong jiang wrote: >> [...] >>> hi, Michal >>> >>> Recently, I hit the same issue when run a OOM case of the LTP and ksm enable. >>> >>> [ 601.937145] Call trace: >>> [ 601.939600] [] __switch_to+0x74/0x8c >>> [ 601.944760] [] __schedule+0x23c/0x7bc >>> [ 601.950007] [] schedule+0x3c/0x94 >>> [ 601.954907] [] rwsem_down_write_failed+0x214/0x350 >>> [ 601.961289] [] down_write+0x64/0x80 >>> [ 601.966363] [] __ksm_exit+0x90/0x19c >>> [ 601.971523] [] mmput+0x118/0x11c >>> [ 601.976335] [] do_exit+0x2dc/0xa74 >>> [ 601.981321] [] do_group_exit+0x4c/0xe4 >>> [ 601.986656] [] get_signal+0x444/0x5e0 >>> [ 601.991904] [] do_signal+0x1d8/0x450 >>> [ 601.997065] [] do_notify_resume+0x70/0x78 >> So this is a hung task triggering because the exiting task cannot get >> the mmap sem for write because the ksmd holds it for read while >> allocating memory which just takes ages to complete, right? >> >>> The root case is that ksmd hold the read lock. and the lock is not released. >>> scan_get_next_rmap_item >>> down_read >>> get_next_rmap_item >>> alloc_rmap_item #ksmd will loop permanently. >>> >>> How do you see this kind of situation ? or let the issue alone. >> I am not familiar with the ksmd code so it is hard for me to judge but >> one thing to do would be __GFP_NORETRY which would force a bail out from >> the allocation rather than looping for ever. A quick look tells me that >> the allocation failure here is quite easy to handle. There might be >> others... >> >> -- >> Michal Hocko >> SUSE Labs Adding the __GFP_NORETRY, the issue also can fixed. Therefore, we can assure that the case of LTP will leads to the endless looping. index d45a0a1..03fb67b 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -283,7 +283,7 @@ static inline struct rmap_item *alloc_rmap_item(void) { struct rmap_item *rmap_item; - rmap_item = kmem_cache_zalloc(rmap_item_cache, GFP_KERNEL); + rmap_item = kmem_cache_zalloc(rmap_item_cache, GFP_KERNEL | __GFP_NORETRY); if (rmap_item) ksm_rmap_items++; return rmap_item; -- 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: email@kvack.org