Hello
shrink_page_list() returns , number of pages reclaimed, when pages is unevictable it returns VM_BUG_ON_PAGE(PageLRU(page) || PageUnevicatble(page),page); We can add the unevictable pages in reclaim list in shrink_page_list(), return total number of reclaim pages including unevictable pages, let the caller handle unevictable pages. I think the problem is shrink_page_list is awkard. If page is unevictable it goto activate_locked->keep_locked->keep lables, keep lable list_add the unevictable pages and throw the VM_BUG instead of passing it to caller while it relies on caller for non-reclaimed-non-unevictable page's putback. I think we can make it consistent so that shrink_page_list could return non-reclaimed pages via page_list and caller can handle it. As an advance, it could try to migrate mlocked pages without retrial. Below is the issue of CMA_ALLOC of large size buffer : (Kernel version - 4.14.65 (On Android pie [ARM])). [ 24.718792] page dumped because: VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page)) [ 24.726949] page->mem_cgroup:bd008c00 [ 24.730693] ------------[ cut here ]------------ [ 24.735304] kernel BUG at mm/vmscan.c:1350! [ 24.739478] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM Below is the patch which solved this issue : diff --git a/mm/vmscan.c b/mm/vmscan.c index be56e2e..12ac353 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -998,7 +998,7 @@ static unsigned long shrink_page_list(struct list_head *page_list, sc->nr_scanned++; if (unlikely(!page_evictable(page))) - goto activate_locked; + goto cull_mlocked; if (!sc->may_unmap && page_mapped(page)) goto keep_locked; @@ -1331,7 +1331,12 @@ static unsigned long shrink_page_list(struct list_head *page_list, } else list_add(&page->lru, &free_pages); continue; - +cull_mlocked: + if (PageSwapCache(page)) + try_to_free_swap(page); + unlock_page(page); + list_add(&page->lru, &ret_pages); + continue; activate_locked: /* Not a candidate for swapping, so reclaim swap space. */ if (PageSwapCache(page) && (mem_cgroup_swap_full(page) || It fixes the below issue. 1. Large size buffer allocation using cma_alloc successful with unevictable pages. cma_alloc of current kernel will fail due to unevictable page Please let me know if anything i am missing. Regards, Pankaj From: Vlastimil Babka <vba...@suse.cz> Sent: 18 March 2019 14:12:50 To: Pankaj Suryawanshi; Kirill Tkhai; Michal Hocko; aneesh.ku...@linux.ibm.com Cc: linux-kernel@vger.kernel.org; minc...@kernel.org; linux...@kvack.org; khand...@linux.vnet.ibm.com; hillf...@alibaba-inc.com Subject: Re: [External] Re: vmscan: Reclaim unevictable pages On 3/15/19 11:11 AM, Pankaj Suryawanshi wrote: > > [ cc Aneesh kumar, Anshuman, Hillf, Vlastimil] Can you send a proper patch with changelog explaining the change? I don't know the context of this thread. > From: Pankaj Suryawanshi > Sent: 15 March 2019 11:35:05 > To: Kirill Tkhai; Michal Hocko > Cc: linux-kernel@vger.kernel.org; minc...@kernel.org; linux...@kvack.org > Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages > > > > [ cc linux-mm ] > > > From: Pankaj Suryawanshi > Sent: 14 March 2019 19:14:40 > To: Kirill Tkhai; Michal Hocko > Cc: linux-kernel@vger.kernel.org; minc...@kernel.org > Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages > > > > Hello , > > Please ignore the curly braces, they are just for debugging. > > Below is the updated patch. > > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index be56e2e..12ac353 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -998,7 +998,7 @@ static unsigned long shrink_page_list(struct list_head > *page_list, > sc->nr_scanned++; > > if (unlikely(!page_evictable(page))) > - goto activate_locked; > + goto cull_mlocked; > > if (!sc->may_unmap && page_mapped(page)) > goto keep_locked; > @@ -1331,7 +1331,12 @@ static unsigned long shrink_page_list(struct list_head > *page_list, > } else > list_add(&page->lru, &free_pages); > continue; > - > +cull_mlocked: > + if (PageSwapCache(page)) > + try_to_free_swap(page); > + unlock_page(page); > + list_add(&page->lru, &ret_pages); > + continue; > activate_locked: > /* Not a candidate for swapping, so reclaim swap space. */ > if (PageSwapCache(page) && (mem_cgroup_swap_full(page) || > > > > Regards, > Pankaj > > > From: Kirill Tkhai <ktk...@virtuozzo.com> > Sent: 14 March 2019 14:55:34 > To: Pankaj Suryawanshi; Michal Hocko > Cc: linux-kernel@vger.kernel.org; minc...@kernel.org > Subject: Re: Re: [External] Re: vmscan: Reclaim unevictable pages > > > On 14.03.2019 11:52, Pankaj Suryawanshi wrote: >> >> I am using kernel version 4.14.65 (on Android pie [ARM]). >> >> No additional patches applied on top of vanilla.(Core MM). >> >> If I change in the vmscan.c as below patch, it will work. > > Sorry, but 4.14.65 does not have braces around trylock_page(), > like in your patch below. > > See > https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/mm/vmscan.c?h=v4.14.65 > > [...] > >>> diff --git a/mm/vmscan.c b/mm/vmscan.c >>> index be56e2e..2e51edc 100644 >>> --- a/mm/vmscan.c >>> +++ b/mm/vmscan.c >>> @@ -990,15 +990,17 @@ static unsigned long shrink_page_list(struct >>> list_head *page_list, >>> page = lru_to_page(page_list); >>> list_del(&page->lru); >>> >>> if (!trylock_page(page)) { >>> goto keep; >>> } > > ************************************************************************************************************************************************************* > eInfochips Business Disclaimer: This e-mail message and all attachments > transmitted with it are intended solely for the use of the addressee and may > contain legally privileged and confidential information. If the reader of > this message is not the intended recipient, or an employee or agent > responsible for delivering this message to the intended recipient, you are > hereby notified that any dissemination, distribution, copying, or other use > of this message or its attachments is strictly prohibited. If you have > received this message in error, please notify the sender immediately by > replying to this message and please delete it from your computer. Any views > expressed in this message are those of the individual sender unless otherwise > stated. Company has taken enough precautions to prevent the spread of > viruses. However the company accepts no liability for any damage caused by > any virus transmitted by this email. > ************************************************************************************************************************************************************* >
