From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f169.google.com (mail-pf0-f169.google.com [209.85.192.169]) by kanga.kvack.org (Postfix) with ESMTP id 7D15B6B0005 for ; Thu, 24 Mar 2016 08:11:05 -0400 (EDT) Received: by mail-pf0-f169.google.com with SMTP id u190so55778890pfb.3 for ; Thu, 24 Mar 2016 05:11:05 -0700 (PDT) Received: from mga02.intel.com (mga02.intel.com. [134.134.136.20]) by mx.google.com with ESMTP id e72si11911159pfb.126.2016.03.24.05.11.04 for ; Thu, 24 Mar 2016 05:11:04 -0700 (PDT) Message-ID: <1458821494.7860.9.camel@linux.intel.com> Subject: Re: [Intel-gfx] [PATCH 1/2] shmem: Support for registration of Driver/file owner specific ops From: Joonas Lahtinen Date: Thu, 24 Mar 2016 14:11:34 +0200 In-Reply-To: <1458713384-25688-1-git-send-email-akash.goel@intel.com> References: <1458713384-25688-1-git-send-email-akash.goel@intel.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: akash.goel@intel.com, intel-gfx@lists.freedesktop.org Cc: linux-mm@kvack.org, Sourab Gupta , Hugh Dickins On ke, 2016-03-23 at 11:39 +0530, akash.goel@intel.com wrote: > From: Chris Wilson > > This provides support for the Drivers or shmem file owners to register > a set of callbacks, which can be invoked from the address space operations > methods implemented by shmem. > This allow the file owners to hook into the shmem address space operations > to do some extra/custom operations in addition to the default ones. > > The private_data field of address_space struct is used to store the pointer > to driver specific ops. > Currently only one ops field is defined, which is migratepage, but can be > extended on need basis. > > The need for driver specific operations arises since some of the operations > (like migratepage) may not be handled completely within shmem, so as to be > effective, and would need some driver specific handling also. > > Specifically, i915.ko would like to participate in migratepage(). > i915.ko uses shmemfs to provide swappable backing storage for its user > objects, but when those objects are in use by the GPU it must pin the entire > object until the GPU is idle. As a result, large chunks of memory can be > arbitrarily withdrawn from page migration, resulting in premature > out-of-memory due to fragmentation. However, if i915.ko can receive the > migratepage() request, it can then flush the object from the GPU, remove > its pin and thus enable the migration. > > Since Gfx allocations are one of the major consumer of system memory, its > imperative to have such a mechanism to effectively deal with fragmentation. > And therefore the need for such a provision for initiating driver specific > actions during address space operations. > > Cc: Hugh Dickins > Cc: linux-mm@kvack.org > Signed-off-by: Sourab Gupta > Signed-off-by: Akash Goel > --- > A include/linux/shmem_fs.h | 17 +++++++++++++++++ > A mm/shmem.cA A A A A A A A A A A A A A A | 17 ++++++++++++++++- > A 2 files changed, 33 insertions(+), 1 deletion(-) > > diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h > index 4d4780c..6cfa76a 100644 > --- a/include/linux/shmem_fs.h > +++ b/include/linux/shmem_fs.h > @@ -34,11 +34,28 @@ struct shmem_sb_info { > A struct mempolicy *mpol;A A A A A /* default memory policy for mappings */ > A }; > A > +struct shmem_dev_info { > + void *dev_private_data; > + int (*dev_migratepage)(struct address_space *mapping, > + A A A A A A A struct page *newpage, struct page *page, > + A A A A A A A enum migrate_mode mode, void *dev_priv_data); One might want to have a separate shmem_dev_operations struct or similar. > +}; > + > A static inline struct shmem_inode_info *SHMEM_I(struct inode *inode) > A { > A return container_of(inode, struct shmem_inode_info, vfs_inode); > A } > A > +static inline int shmem_set_device_ops(struct address_space *mapping, > + struct shmem_dev_info *info) > +{ > + if (mapping->private_data != NULL) > + return -EEXIST; > + I did a quick random peek and most set functions are just void and override existing data. I'd suggest the same. > + mapping->private_data = info; Also, doesn't this kinda steal the mapping->private_data, might that be unexpected for the user? I notice currently it's not being touched at all. > + return 0; > +} > + > A /* > A * Functions in mm/shmem.c called directly from elsewhere: > A */ > diff --git a/mm/shmem.c b/mm/shmem.c > index 440e2a7..f8625c4 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -952,6 +952,21 @@ redirty: > A return 0; > A } > A > +#ifdef CONFIG_MIGRATION > +static int shmem_migratepage(struct address_space *mapping, > + A A A A A struct page *newpage, struct page *page, > + A A A A A enum migrate_mode mode) > +{ > + struct shmem_dev_info *dev_info = mapping->private_data; > + > + if (dev_info && dev_info->dev_migratepage) > + return dev_info->dev_migratepage(mapping, newpage, page, > + mode, dev_info->dev_private_data); > + > + return migrate_page(mapping, newpage, page, mode); > +} > +#endif > + > A #ifdef CONFIG_NUMA > A #ifdef CONFIG_TMPFS > A static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol) > @@ -3168,7 +3183,7 @@ static const struct address_space_operations shmem_aops = { > A .write_end = shmem_write_end, > A #endif > A #ifdef CONFIG_MIGRATION > - .migratepage = migrate_page, > + .migratepage = shmem_migratepage, > A #endif > A .error_remove_page = generic_error_remove_page, > A }; -- Joonas Lahtinen Open Source Technology Center Intel Corporation -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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