From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qg0-f48.google.com (mail-qg0-f48.google.com [209.85.192.48]) by kanga.kvack.org (Postfix) with ESMTP id 502BD4402FE for ; Fri, 2 Oct 2015 18:37:05 -0400 (EDT) Received: by qgt47 with SMTP id 47so107275717qgt.2 for ; Fri, 02 Oct 2015 15:37:05 -0700 (PDT) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id e13si12287989qhc.3.2015.10.02.15.37.04 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 02 Oct 2015 15:37:04 -0700 (PDT) Date: Fri, 2 Oct 2015 15:37:02 -0700 From: Andrew Morton Subject: Re: [PATCH v4 2/4] mm, proc: account for shmem swap in /proc/pid/smaps Message-Id: <20151002153702.7bdc4c0483cd9b2ee9e0fba3@linux-foundation.org> In-Reply-To: <1443792951-13944-3-git-send-email-vbabka@suse.cz> References: <1443792951-13944-1-git-send-email-vbabka@suse.cz> <1443792951-13944-3-git-send-email-vbabka@suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Vlastimil Babka Cc: linux-mm@kvack.org, Jerome Marchand , Hugh Dickins , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, Michal Hocko , "Kirill A. Shutemov" , Cyrill Gorcunov , Randy Dunlap , linux-s390@vger.kernel.org, Martin Schwidefsky , Heiko Carstens , Peter Zijlstra , Paul Mackerras , Arnaldo Carvalho de Melo , Oleg Nesterov , Linux API , Konstantin Khlebnikov On Fri, 2 Oct 2015 15:35:49 +0200 Vlastimil Babka wrote: > Currently, /proc/pid/smaps will always show "Swap: 0 kB" for shmem-backed > mappings, even if the mapped portion does contain pages that were swapped out. > This is because unlike private anonymous mappings, shmem does not change pte > to swap entry, but pte_none when swapping the page out. In the smaps page > walk, such page thus looks like it was never faulted in. > > This patch changes smaps_pte_entry() to determine the swap status for such > pte_none entries for shmem mappings, similarly to how mincore_page() does it. > Swapped out pages are thus accounted for. > > The accounting is arguably still not as precise as for private anonymous > mappings, since now we will count also pages that the process in question never > accessed, but only another process populated them and then let them become > swapped out. I believe it is still less confusing and subtle than not showing > any swap usage by shmem mappings at all. Also, swapped out pages only becomee a > performance issue for future accesses, and we cannot predict those for neither > kind of mapping. > > ... > > --- a/include/linux/shmem_fs.h > +++ b/include/linux/shmem_fs.h > @@ -60,6 +60,12 @@ extern struct page *shmem_read_mapping_page_gfp(struct address_space *mapping, > extern void shmem_truncate_range(struct inode *inode, loff_t start, loff_t end); > extern int shmem_unuse(swp_entry_t entry, struct page *page); > > +#ifdef CONFIG_SWAP > +extern unsigned long shmem_swap_usage(struct inode *inode); > +extern unsigned long shmem_partial_swap_usage(struct address_space *mapping, > + pgoff_t start, pgoff_t end); > +#endif CONFIG_SWAP is wrong, isn't it? It should be CONFIG_SHMEM if anything. I'd just do --- a/include/linux/shmem_fs.h~mm-proc-account-for-shmem-swap-in-proc-pid-smaps-fix +++ a/include/linux/shmem_fs.h @@ -60,11 +60,9 @@ extern struct page *shmem_read_mapping_p extern void shmem_truncate_range(struct inode *inode, loff_t start, loff_t end); extern int shmem_unuse(swp_entry_t entry, struct page *page); -#ifdef CONFIG_SWAP extern unsigned long shmem_swap_usage(struct inode *inode); extern unsigned long shmem_partial_swap_usage(struct address_space *mapping, pgoff_t start, pgoff_t end); -#endif static inline struct page *shmem_read_mapping_page( struct address_space *mapping, pgoff_t index) We don't need the ifdefs around declarations and they're a pain to maintain and they'd add a *ton* of clutter if we even tried to do this for real. -- 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