Messages in this thread | | | Subject | Re: [PATCH v4 3/4] mm/page_reporting: Allow driver to specify reporting order | From | Gavin Shan <> | Date | Fri, 25 Jun 2021 14:24:06 +1000 |
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On 6/25/21 2:00 PM, Gavin Shan wrote: > On 6/25/21 11:19 AM, Alexander Duyck wrote: >> On Thu, Jun 24, 2021 at 4:46 PM Gavin Shan <gshan@redhat.com> wrote: >>> >>> The page reporting order (threshold) is sticky to @pageblock_order >>> by default. The page reporting can never be triggered because the >>> freeing page can't come up with a free area like that huge. The >>> situation becomes worse when the system memory becomes heavily >>> fragmented. >>> >>> For example, the following configurations are used on ARM64 when 64KB >>> base page size is enabled. In this specific case, the page reporting >>> won't be triggered until the freeing page comes up with a 512MB free >>> area. That's hard to be met, especially when the system memory becomes >>> heavily fragmented. >>> >>> PAGE_SIZE: 64KB >>> HPAGE_SIZE: 512MB >>> pageblock_order: 13 (512MB) >>> MAX_ORDER: 14 >>> >>> This allows the drivers to specify the page reporting order when the >>> page reporting device is registered. It falls back to @pageblock_order >>> if it's not specified by the driver. The existing users (hv_balloon >>> and virtio_balloon) don't specify it and @pageblock_order is still >>> taken as their page reporting order. So this shouldn't introduce any >>> functional changes. >>> >>> Signed-off-by: Gavin Shan <gshan@redhat.com> >>> Reviewed-by: Alexander Duyck <alexanderduyck@fb.com> >>> --- >>> include/linux/page_reporting.h | 3 +++ >>> mm/page_reporting.c | 6 ++++++ >>> 2 files changed, 9 insertions(+) >>> >>> diff --git a/include/linux/page_reporting.h b/include/linux/page_reporting.h >>> index 3b99e0ec24f2..fe648dfa3a7c 100644 >>> --- a/include/linux/page_reporting.h >>> +++ b/include/linux/page_reporting.h >>> @@ -18,6 +18,9 @@ struct page_reporting_dev_info { >>> >>> /* Current state of page reporting */ >>> atomic_t state; >>> + >>> + /* Minimal order of page reporting */ >>> + unsigned int order; >>> }; >>> >>> /* Tear-down and bring-up for page reporting devices */ >>> diff --git a/mm/page_reporting.c b/mm/page_reporting.c >>> index 34bf4d26c2c4..382958eef8a9 100644 >>> --- a/mm/page_reporting.c >>> +++ b/mm/page_reporting.c >>> @@ -329,6 +329,12 @@ int page_reporting_register(struct page_reporting_dev_info *prdev) >>> goto err_out; >>> } >>> >>> + /* >>> + * Update the page reporting order if it's specified by driver. >>> + * Otherwise, it falls back to @pageblock_order. >>> + */ >>> + page_reporting_order = prdev->order ? : pageblock_order; >>> + >> >> An alternative to this would be to look at setting up some >> comparisons. I might add another variable and do something like: >> order = prdev->order ? : pageblock_order; >> if (order < page_reporting_order) >> page_reporting_order = order; >> >> You could essentially do something similar in the previous patch but >> just use pageblock_order directly rather than having to add a local >> variable. >> >> That way if you need to still pull down the page reporting order you >> can do so without prdev->order or pageblock_order overwriting the >> value and pushing it back up. >> > > Thanks, Alex. Lets do both in v5, which will be posted shortly. >
Alex, I just posted v5 to have the checks you suggested. Could you help to have a quick scan. It's pointless to let Andrew drop the patches and apply the last one again :)
Thanks, Gavin
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