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Tsirkin" To: Gavin Shan Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, alexander.duyck@gmail.com, david@redhat.com, akpm@linux-foundation.org, anshuman.khandual@arm.com, catalin.marinas@arm.com, will@kernel.org, shan.gavin@gmail.com Subject: Re: [PATCH v4 2/4] mm/page_reporting: Export reporting order as module parameter Message-ID: <20210625014928-mutt-send-email-mst@kernel.org> References: <20210625014710.42954-1-gshan@redhat.com> <20210625014710.42954-3-gshan@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210625014710.42954-3-gshan@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 25, 2021 at 09:47:08AM +0800, Gavin Shan wrote: > The macro PAGE_REPORTING_MIN_ORDER is defined as the page reporting > threshold. It can't be adjusted at runtime. > > This introduces a variable (@page_reporting_order) to replace the > marcro (PAGE_REPORTING_MIN_ORDER). MAX_ORDER is assigned to it initially, > meaning the page reporting is disabled. It will be specified by driver > if valid one is provided. Otherwise, it will fall back to @pageblock_order. > It's also exported so that the page reporting order can be adjusted at > runtime. > > Suggested-by: David Hildenbrand > Signed-off-by: Gavin Shan > Reviewed-by: Alexander Duyck > --- > Documentation/admin-guide/kernel-parameters.txt | 6 ++++++ > mm/page_reporting.c | 9 +++++++-- > mm/page_reporting.h | 5 ++--- > 3 files changed, 15 insertions(+), 5 deletions(-) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index cb89dbdedc46..566c4b9af3cd 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -3566,6 +3566,12 @@ > off: turn off poisoning (default) > on: turn on poisoning > > + page_reporting.page_reporting_order= > + [KNL] Minimal page reporting order > + Format: > + Adjust the minimal page reporting order. The page > + reporting is disabled when it exceeds (MAX_ORDER-1). Which the admin knows how? Run grep in the kernel source? > + > panic= [KNL] Kernel behaviour on panic: delay > timeout > 0: seconds before rebooting > timeout = 0: wait forever > diff --git a/mm/page_reporting.c b/mm/page_reporting.c > index df9c5054e1b4..34bf4d26c2c4 100644 > --- a/mm/page_reporting.c > +++ b/mm/page_reporting.c > @@ -4,12 +4,17 @@ > #include > #include > #include > +#include > #include > #include > > #include "page_reporting.h" > #include "internal.h" > > +unsigned int page_reporting_order = MAX_ORDER; > +module_param(page_reporting_order, uint, 0644); > +MODULE_PARM_DESC(page_reporting_order, "Set page reporting order"); > + > #define PAGE_REPORTING_DELAY (2 * HZ) > static struct page_reporting_dev_info __rcu *pr_dev_info __read_mostly; > > @@ -229,7 +234,7 @@ page_reporting_process_zone(struct page_reporting_dev_info *prdev, > > /* Generate minimum watermark to be able to guarantee progress */ > watermark = low_wmark_pages(zone) + > - (PAGE_REPORTING_CAPACITY << PAGE_REPORTING_MIN_ORDER); > + (PAGE_REPORTING_CAPACITY << page_reporting_order); Looks like this makes it easy to trigger undefined behaviour. Just use any value > 31. > > /* > * Cancel request if insufficient free memory or if we failed > @@ -239,7 +244,7 @@ page_reporting_process_zone(struct page_reporting_dev_info *prdev, > return err; > > /* Process each free list starting from lowest order/mt */ > - for (order = PAGE_REPORTING_MIN_ORDER; order < MAX_ORDER; order++) { > + for (order = page_reporting_order; order < MAX_ORDER; order++) { > for (mt = 0; mt < MIGRATE_TYPES; mt++) { > /* We do not pull pages from the isolate free list */ > if (is_migrate_isolate(mt)) > diff --git a/mm/page_reporting.h b/mm/page_reporting.h > index 2c385dd4ddbd..c51dbc228b94 100644 > --- a/mm/page_reporting.h > +++ b/mm/page_reporting.h > @@ -10,10 +10,9 @@ > #include > #include > > -#define PAGE_REPORTING_MIN_ORDER pageblock_order > - > #ifdef CONFIG_PAGE_REPORTING > DECLARE_STATIC_KEY_FALSE(page_reporting_enabled); > +extern unsigned int page_reporting_order; > void __page_reporting_notify(void); > > static inline bool page_reported(struct page *page) > @@ -38,7 +37,7 @@ static inline void page_reporting_notify_free(unsigned int order) > return; > > /* Determine if we have crossed reporting threshold */ > - if (order < PAGE_REPORTING_MIN_ORDER) > + if (order < page_reporting_order) > return; > > /* This will add a few cycles, but should be called infrequently */ > -- > 2.23.0