| Message ID | 20190206235706.4851-4-namit@vmware.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | vmw_balloon: 64-bit limit support, compaction, shrinker | expand |
On Wed, Feb 06, 2019 at 03:57:03PM -0800, Nadav Amit wrote: > Introduce interfaces for ballooning enqueueing and dequeueing of a list > of pages. These interfaces reduce the overhead of storing and restoring > IRQs by batching the operations. In addition they do not panic if the > list of pages is empty. > > Cc: "Michael S. Tsirkin" <mst@redhat.com> > Cc: Jason Wang <jasowang@redhat.com> > Cc: linux-mm@kvack.org > Cc: virtualization@lists.linux-foundation.org > Reviewed-by: Xavier Deguillard <xdeguillard@vmware.com> > Signed-off-by: Nadav Amit <namit@vmware.com> > --- > include/linux/balloon_compaction.h | 4 + > mm/balloon_compaction.c | 139 +++++++++++++++++++++-------- > 2 files changed, 105 insertions(+), 38 deletions(-) > > diff --git a/include/linux/balloon_compaction.h b/include/linux/balloon_compaction.h > index 53051f3d8f25..2c5a8e09e413 100644 > --- a/include/linux/balloon_compaction.h > +++ b/include/linux/balloon_compaction.h > @@ -72,6 +72,10 @@ extern struct page *balloon_page_alloc(void); > extern void balloon_page_enqueue(struct balloon_dev_info *b_dev_info, > struct page *page); > extern struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info); > +extern void balloon_page_list_enqueue(struct balloon_dev_info *b_dev_info, > + struct list_head *pages); > +extern int balloon_page_list_dequeue(struct balloon_dev_info *b_dev_info, > + struct list_head *pages, int n_req_pages); > > static inline void balloon_devinfo_init(struct balloon_dev_info *balloon) > { > diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c > index ef858d547e2d..b8e82864f82c 100644 > --- a/mm/balloon_compaction.c > +++ b/mm/balloon_compaction.c > @@ -10,6 +10,100 @@ > #include <linux/export.h> > #include <linux/balloon_compaction.h> > > +static int balloon_page_enqueue_one(struct balloon_dev_info *b_dev_info, > + struct page *page) > +{ > + /* > + * Block others from accessing the 'page' when we get around to > + * establishing additional references. We should be the only one > + * holding a reference to the 'page' at this point. > + */ > + if (!trylock_page(page)) { > + WARN_ONCE(1, "balloon inflation failed to enqueue page\n"); > + return -EFAULT; > + } > + list_del(&page->lru); > + balloon_page_insert(b_dev_info, page); > + unlock_page(page); > + __count_vm_event(BALLOON_INFLATE); > + return 0; > +} > + > +/** > + * balloon_page_list_enqueue() - inserts a list of pages into the balloon page > + * list. > + * @b_dev_info: balloon device descriptor where we will insert a new page to > + * @pages: pages to enqueue - allocated using balloon_page_alloc. > + * > + * Driver must call it to properly enqueue a balloon pages before definitively > + * removing it from the guest system. > + */ > +void balloon_page_list_enqueue(struct balloon_dev_info *b_dev_info, > + struct list_head *pages) > +{ > + struct page *page, *tmp; > + unsigned long flags; > + > + spin_lock_irqsave(&b_dev_info->pages_lock, flags); > + list_for_each_entry_safe(page, tmp, pages, lru) > + balloon_page_enqueue_one(b_dev_info, page); > + spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); As this is scanning pages one by one anyway, it will be useful to have this return the # of pages enqueued. > +} > +EXPORT_SYMBOL_GPL(balloon_page_list_enqueue); > + > +/** > + * balloon_page_list_dequeue() - removes pages from balloon's page list and > + * returns a list of the pages. > + * @b_dev_info: balloon device decriptor where we will grab a page from. > + * @pages: pointer to the list of pages that would be returned to the caller. > + * @n_req_pages: number of requested pages. > + * > + * Driver must call it to properly de-allocate a previous enlisted balloon pages > + * before definetively releasing it back to the guest system. This function > + * tries to remove @n_req_pages from the ballooned pages and return it to the > + * caller in the @pages list. > + * > + * Note that this function may fail to dequeue some pages temporarily empty due > + * to compaction isolated pages. > + * > + * Return: number of pages that were added to the @pages list. > + */ > +int balloon_page_list_dequeue(struct balloon_dev_info *b_dev_info, > + struct list_head *pages, int n_req_pages) Are we sure this int never overflows? Why not just use u64 or size_t straight away? > +{ > + struct page *page, *tmp; > + unsigned long flags; > + int n_pages = 0; > + > + spin_lock_irqsave(&b_dev_info->pages_lock, flags); > + list_for_each_entry_safe(page, tmp, &b_dev_info->pages, lru) { > + /* > + * Block others from accessing the 'page' while we get around > + * establishing additional references and preparing the 'page' > + * to be released by the balloon driver. > + */ > + if (!trylock_page(page)) > + continue; > + > + if (IS_ENABLED(CONFIG_BALLOON_COMPACTION) && > + PageIsolated(page)) { > + /* raced with isolation */ > + unlock_page(page); > + continue; > + } > + balloon_page_delete(page); > + __count_vm_event(BALLOON_DEFLATE); > + unlock_page(page); > + list_add(&page->lru, pages); > + if (++n_pages >= n_req_pages) > + break; > + } > + spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); > + > + return n_pages; > +} > +EXPORT_SYMBOL_GPL(balloon_page_list_dequeue); > + This looks quite reasonable. In fact virtio can be reworked to use this too and then the original one can be dropped. Have the time? > /* > * balloon_page_alloc - allocates a new page for insertion into the balloon > * page list. > @@ -43,17 +137,9 @@ void balloon_page_enqueue(struct balloon_dev_info *b_dev_info, > { > unsigned long flags; > > - /* > - * Block others from accessing the 'page' when we get around to > - * establishing additional references. We should be the only one > - * holding a reference to the 'page' at this point. > - */ > - BUG_ON(!trylock_page(page)); > spin_lock_irqsave(&b_dev_info->pages_lock, flags); > - balloon_page_insert(b_dev_info, page); > - __count_vm_event(BALLOON_INFLATE); > + balloon_page_enqueue_one(b_dev_info, page); > spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); > - unlock_page(page); > } > EXPORT_SYMBOL_GPL(balloon_page_enqueue); > > @@ -70,36 +156,13 @@ EXPORT_SYMBOL_GPL(balloon_page_enqueue); > */ > struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info) > { > - struct page *page, *tmp; > unsigned long flags; > - bool dequeued_page; > + LIST_HEAD(pages); > + int n_pages; > > - dequeued_page = false; > - spin_lock_irqsave(&b_dev_info->pages_lock, flags); > - list_for_each_entry_safe(page, tmp, &b_dev_info->pages, lru) { > - /* > - * Block others from accessing the 'page' while we get around > - * establishing additional references and preparing the 'page' > - * to be released by the balloon driver. > - */ > - if (trylock_page(page)) { > -#ifdef CONFIG_BALLOON_COMPACTION > - if (PageIsolated(page)) { > - /* raced with isolation */ > - unlock_page(page); > - continue; > - } > -#endif > - balloon_page_delete(page); > - __count_vm_event(BALLOON_DEFLATE); > - unlock_page(page); > - dequeued_page = true; > - break; > - } > - } > - spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); > + n_pages = balloon_page_list_dequeue(b_dev_info, &pages, 1); > > - if (!dequeued_page) { > + if (n_pages != 1) { > /* > * If we are unable to dequeue a balloon page because the page > * list is empty and there is no isolated pages, then something > @@ -112,9 +175,9 @@ struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info) > !b_dev_info->isolated_pages)) > BUG(); > spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); > - page = NULL; > + return NULL; > } > - return page; > + return list_first_entry(&pages, struct page, lru); > } > EXPORT_SYMBOL_GPL(balloon_page_dequeue); > > -- > 2.17.1
> On Feb 6, 2019, at 4:32 PM, Michael S. Tsirkin <mst@redhat.com> wrote: > > On Wed, Feb 06, 2019 at 03:57:03PM -0800, Nadav Amit wrote: >> Introduce interfaces for ballooning enqueueing and dequeueing of a list >> of pages. These interfaces reduce the overhead of storing and restoring >> IRQs by batching the operations. In addition they do not panic if the >> list of pages is empty. >> [Snip] First, thanks for the quick feedback. >> + >> +/** >> + * balloon_page_list_enqueue() - inserts a list of pages into the balloon page >> + * list. >> + * @b_dev_info: balloon device descriptor where we will insert a new page to >> + * @pages: pages to enqueue - allocated using balloon_page_alloc. >> + * >> + * Driver must call it to properly enqueue a balloon pages before definitively >> + * removing it from the guest system. >> + */ >> +void balloon_page_list_enqueue(struct balloon_dev_info *b_dev_info, >> + struct list_head *pages) >> +{ >> + struct page *page, *tmp; >> + unsigned long flags; >> + >> + spin_lock_irqsave(&b_dev_info->pages_lock, flags); >> + list_for_each_entry_safe(page, tmp, pages, lru) >> + balloon_page_enqueue_one(b_dev_info, page); >> + spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); > > As this is scanning pages one by one anyway, it will be useful > to have this return the # of pages enqueued. Sure. > >> +} >> +EXPORT_SYMBOL_GPL(balloon_page_list_enqueue); >> + >> +/** >> + * balloon_page_list_dequeue() - removes pages from balloon's page list and >> + * returns a list of the pages. >> + * @b_dev_info: balloon device decriptor where we will grab a page from. >> + * @pages: pointer to the list of pages that would be returned to the caller. >> + * @n_req_pages: number of requested pages. >> + * >> + * Driver must call it to properly de-allocate a previous enlisted balloon pages >> + * before definetively releasing it back to the guest system. This function >> + * tries to remove @n_req_pages from the ballooned pages and return it to the >> + * caller in the @pages list. >> + * >> + * Note that this function may fail to dequeue some pages temporarily empty due >> + * to compaction isolated pages. >> + * >> + * Return: number of pages that were added to the @pages list. >> + */ >> +int balloon_page_list_dequeue(struct balloon_dev_info *b_dev_info, >> + struct list_head *pages, int n_req_pages) > > Are we sure this int never overflows? Why not just use u64 > or size_t straight away? size_t it is. > >> +{ >> + struct page *page, *tmp; >> + unsigned long flags; >> + int n_pages = 0; >> + >> + spin_lock_irqsave(&b_dev_info->pages_lock, flags); >> + list_for_each_entry_safe(page, tmp, &b_dev_info->pages, lru) { >> + /* >> + * Block others from accessing the 'page' while we get around >> + * establishing additional references and preparing the 'page' >> + * to be released by the balloon driver. >> + */ >> + if (!trylock_page(page)) >> + continue; >> + >> + if (IS_ENABLED(CONFIG_BALLOON_COMPACTION) && >> + PageIsolated(page)) { >> + /* raced with isolation */ >> + unlock_page(page); >> + continue; >> + } >> + balloon_page_delete(page); >> + __count_vm_event(BALLOON_DEFLATE); >> + unlock_page(page); >> + list_add(&page->lru, pages); >> + if (++n_pages >= n_req_pages) >> + break; >> + } >> + spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); >> + >> + return n_pages; >> +} >> +EXPORT_SYMBOL_GPL(balloon_page_list_dequeue); >> + > > This looks quite reasonable. In fact virtio can be reworked to use > this too and then the original one can be dropped. > > Have the time? Obviously not, but I am willing to make the time. What I cannot “make" is an approval to send patches for other hypervisors. Let me run a quick check with our FOSS people here. Anyhow, I hope it would not prevent the patches from getting to the next release.
On Thu, Feb 07, 2019 at 12:43:51AM +0000, Nadav Amit wrote: > > On Feb 6, 2019, at 4:32 PM, Michael S. Tsirkin <mst@redhat.com> wrote: > > > > On Wed, Feb 06, 2019 at 03:57:03PM -0800, Nadav Amit wrote: > >> Introduce interfaces for ballooning enqueueing and dequeueing of a list > >> of pages. These interfaces reduce the overhead of storing and restoring > >> IRQs by batching the operations. In addition they do not panic if the > >> list of pages is empty. > >> > > [Snip] > > First, thanks for the quick feedback. > > >> + > >> +/** > >> + * balloon_page_list_enqueue() - inserts a list of pages into the balloon page > >> + * list. > >> + * @b_dev_info: balloon device descriptor where we will insert a new page to > >> + * @pages: pages to enqueue - allocated using balloon_page_alloc. > >> + * > >> + * Driver must call it to properly enqueue a balloon pages before definitively > >> + * removing it from the guest system. > >> + */ > >> +void balloon_page_list_enqueue(struct balloon_dev_info *b_dev_info, > >> + struct list_head *pages) > >> +{ > >> + struct page *page, *tmp; > >> + unsigned long flags; > >> + > >> + spin_lock_irqsave(&b_dev_info->pages_lock, flags); > >> + list_for_each_entry_safe(page, tmp, pages, lru) > >> + balloon_page_enqueue_one(b_dev_info, page); > >> + spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); > > > > As this is scanning pages one by one anyway, it will be useful > > to have this return the # of pages enqueued. > > Sure. > > > > >> +} > >> +EXPORT_SYMBOL_GPL(balloon_page_list_enqueue); > >> + > >> +/** > >> + * balloon_page_list_dequeue() - removes pages from balloon's page list and > >> + * returns a list of the pages. > >> + * @b_dev_info: balloon device decriptor where we will grab a page from. > >> + * @pages: pointer to the list of pages that would be returned to the caller. > >> + * @n_req_pages: number of requested pages. > >> + * > >> + * Driver must call it to properly de-allocate a previous enlisted balloon pages > >> + * before definetively releasing it back to the guest system. This function > >> + * tries to remove @n_req_pages from the ballooned pages and return it to the > >> + * caller in the @pages list. > >> + * > >> + * Note that this function may fail to dequeue some pages temporarily empty due > >> + * to compaction isolated pages. > >> + * > >> + * Return: number of pages that were added to the @pages list. > >> + */ > >> +int balloon_page_list_dequeue(struct balloon_dev_info *b_dev_info, > >> + struct list_head *pages, int n_req_pages) > > > > Are we sure this int never overflows? Why not just use u64 > > or size_t straight away? > > size_t it is. > > > > >> +{ > >> + struct page *page, *tmp; > >> + unsigned long flags; > >> + int n_pages = 0; > >> + > >> + spin_lock_irqsave(&b_dev_info->pages_lock, flags); > >> + list_for_each_entry_safe(page, tmp, &b_dev_info->pages, lru) { > >> + /* > >> + * Block others from accessing the 'page' while we get around > >> + * establishing additional references and preparing the 'page' > >> + * to be released by the balloon driver. > >> + */ > >> + if (!trylock_page(page)) > >> + continue; > >> + > >> + if (IS_ENABLED(CONFIG_BALLOON_COMPACTION) && > >> + PageIsolated(page)) { > >> + /* raced with isolation */ > >> + unlock_page(page); > >> + continue; > >> + } > >> + balloon_page_delete(page); > >> + __count_vm_event(BALLOON_DEFLATE); > >> + unlock_page(page); > >> + list_add(&page->lru, pages); > >> + if (++n_pages >= n_req_pages) > >> + break; > >> + } > >> + spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); > >> + > >> + return n_pages; > >> +} > >> +EXPORT_SYMBOL_GPL(balloon_page_list_dequeue); > >> + > > > > This looks quite reasonable. In fact virtio can be reworked to use > > this too and then the original one can be dropped. > > > > Have the time? > > Obviously not, but I am willing to make the time. What I cannot “make" is an > approval to send patches for other hypervisors. Let me run a quick check > with our FOSS people here. > > Anyhow, I hope it would not prevent the patches from getting to the next > release. > No, that's not a blocker.
diff --git a/include/linux/balloon_compaction.h b/include/linux/balloon_compaction.h index 53051f3d8f25..2c5a8e09e413 100644 --- a/include/linux/balloon_compaction.h +++ b/include/linux/balloon_compaction.h @@ -72,6 +72,10 @@ extern struct page *balloon_page_alloc(void); extern void balloon_page_enqueue(struct balloon_dev_info *b_dev_info, struct page *page); extern struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info); +extern void balloon_page_list_enqueue(struct balloon_dev_info *b_dev_info, + struct list_head *pages); +extern int balloon_page_list_dequeue(struct balloon_dev_info *b_dev_info, + struct list_head *pages, int n_req_pages); static inline void balloon_devinfo_init(struct balloon_dev_info *balloon) { diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c index ef858d547e2d..b8e82864f82c 100644 --- a/mm/balloon_compaction.c +++ b/mm/balloon_compaction.c @@ -10,6 +10,100 @@ #include <linux/export.h> #include <linux/balloon_compaction.h> +static int balloon_page_enqueue_one(struct balloon_dev_info *b_dev_info, + struct page *page) +{ + /* + * Block others from accessing the 'page' when we get around to + * establishing additional references. We should be the only one + * holding a reference to the 'page' at this point. + */ + if (!trylock_page(page)) { + WARN_ONCE(1, "balloon inflation failed to enqueue page\n"); + return -EFAULT; + } + list_del(&page->lru); + balloon_page_insert(b_dev_info, page); + unlock_page(page); + __count_vm_event(BALLOON_INFLATE); + return 0; +} + +/** + * balloon_page_list_enqueue() - inserts a list of pages into the balloon page + * list. + * @b_dev_info: balloon device descriptor where we will insert a new page to + * @pages: pages to enqueue - allocated using balloon_page_alloc. + * + * Driver must call it to properly enqueue a balloon pages before definitively + * removing it from the guest system. + */ +void balloon_page_list_enqueue(struct balloon_dev_info *b_dev_info, + struct list_head *pages) +{ + struct page *page, *tmp; + unsigned long flags; + + spin_lock_irqsave(&b_dev_info->pages_lock, flags); + list_for_each_entry_safe(page, tmp, pages, lru) + balloon_page_enqueue_one(b_dev_info, page); + spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); +} +EXPORT_SYMBOL_GPL(balloon_page_list_enqueue); + +/** + * balloon_page_list_dequeue() - removes pages from balloon's page list and + * returns a list of the pages. + * @b_dev_info: balloon device decriptor where we will grab a page from. + * @pages: pointer to the list of pages that would be returned to the caller. + * @n_req_pages: number of requested pages. + * + * Driver must call it to properly de-allocate a previous enlisted balloon pages + * before definetively releasing it back to the guest system. This function + * tries to remove @n_req_pages from the ballooned pages and return it to the + * caller in the @pages list. + * + * Note that this function may fail to dequeue some pages temporarily empty due + * to compaction isolated pages. + * + * Return: number of pages that were added to the @pages list. + */ +int balloon_page_list_dequeue(struct balloon_dev_info *b_dev_info, + struct list_head *pages, int n_req_pages) +{ + struct page *page, *tmp; + unsigned long flags; + int n_pages = 0; + + spin_lock_irqsave(&b_dev_info->pages_lock, flags); + list_for_each_entry_safe(page, tmp, &b_dev_info->pages, lru) { + /* + * Block others from accessing the 'page' while we get around + * establishing additional references and preparing the 'page' + * to be released by the balloon driver. + */ + if (!trylock_page(page)) + continue; + + if (IS_ENABLED(CONFIG_BALLOON_COMPACTION) && + PageIsolated(page)) { + /* raced with isolation */ + unlock_page(page); + continue; + } + balloon_page_delete(page); + __count_vm_event(BALLOON_DEFLATE); + unlock_page(page); + list_add(&page->lru, pages); + if (++n_pages >= n_req_pages) + break; + } + spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); + + return n_pages; +} +EXPORT_SYMBOL_GPL(balloon_page_list_dequeue); + /* * balloon_page_alloc - allocates a new page for insertion into the balloon * page list. @@ -43,17 +137,9 @@ void balloon_page_enqueue(struct balloon_dev_info *b_dev_info, { unsigned long flags; - /* - * Block others from accessing the 'page' when we get around to - * establishing additional references. We should be the only one - * holding a reference to the 'page' at this point. - */ - BUG_ON(!trylock_page(page)); spin_lock_irqsave(&b_dev_info->pages_lock, flags); - balloon_page_insert(b_dev_info, page); - __count_vm_event(BALLOON_INFLATE); + balloon_page_enqueue_one(b_dev_info, page); spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); - unlock_page(page); } EXPORT_SYMBOL_GPL(balloon_page_enqueue); @@ -70,36 +156,13 @@ EXPORT_SYMBOL_GPL(balloon_page_enqueue); */ struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info) { - struct page *page, *tmp; unsigned long flags; - bool dequeued_page; + LIST_HEAD(pages); + int n_pages; - dequeued_page = false; - spin_lock_irqsave(&b_dev_info->pages_lock, flags); - list_for_each_entry_safe(page, tmp, &b_dev_info->pages, lru) { - /* - * Block others from accessing the 'page' while we get around - * establishing additional references and preparing the 'page' - * to be released by the balloon driver. - */ - if (trylock_page(page)) { -#ifdef CONFIG_BALLOON_COMPACTION - if (PageIsolated(page)) { - /* raced with isolation */ - unlock_page(page); - continue; - } -#endif - balloon_page_delete(page); - __count_vm_event(BALLOON_DEFLATE); - unlock_page(page); - dequeued_page = true; - break; - } - } - spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); + n_pages = balloon_page_list_dequeue(b_dev_info, &pages, 1); - if (!dequeued_page) { + if (n_pages != 1) { /* * If we are unable to dequeue a balloon page because the page * list is empty and there is no isolated pages, then something @@ -112,9 +175,9 @@ struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info) !b_dev_info->isolated_pages)) BUG(); spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); - page = NULL; + return NULL; } - return page; + return list_first_entry(&pages, struct page, lru); } EXPORT_SYMBOL_GPL(balloon_page_dequeue);