Hi, I agree that hooking alloc_pages is ugly way. So alternatives I see: - shrinkers (as e.g. Android OOM used) but shrink_slab called only from try_to_free_pages only if we are on slow reclaim path on memory allocation, so it cannot be used for e.g. 75% memory tracking or when pages released to notify user space that we are OK. But according to easy to use it will be the best approach. - memcg-kind of changes like mem_cgroup_newpage_charge/uncharge_page but without blocking decision making logic. Seems to me more changes. Threshold currently in memcg set 128 pages per CPU, that is quite often for level tracking needs. - tracking situation using timer? Maybe not due to will impact battery. With Best Wishes, Leonid -----Original Message----- From: ext KAMEZAWA Hiroyuki [mailto:kamezawa.hiroyu@xxxxxxxxxxxxxx] Sent: 05 January, 2012 09:00 To: Moiseichuk Leonid (Nokia-MP/Helsinki) Cc: linux-mm@xxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; cesarb@xxxxxxxxxx; emunson@xxxxxxxxx; penberg@xxxxxxxxxx; aarcange@xxxxxxxxxx; riel@xxxxxxxxxx; mel@xxxxxxxxx; rientjes@xxxxxxxxxx; dima@xxxxxxxxxxx; gregkh@xxxxxxx; rebecca@xxxxxxxxxxx; san@xxxxxxxxxx; akpm@xxxxxxxxxxxxxxxxxxxx; Jaaskelainen Vesa (Nokia-MP/Helsinki) Subject: Re: [PATCH 3.2.0-rc1 2/3] MM hook for page allocation and release On Wed, 4 Jan 2012 19:21:55 +0200 Leonid Moiseichuk <leonid.moiseichuk@xxxxxxxxx> wrote: > That is required by Used Memory Meter (UMM) pseudo-device to track > memory utilization in system. It is expected that hook MUST be very > light to prevent performance impact on the hot allocation path. > Accuracy of number managed pages does not expected to be absolute but > fact of allocation or deallocation must be registered. > > Signed-off-by: Leonid Moiseichuk <leonid.moiseichuk@xxxxxxxxx> I never like arbitrary hooks to alloc_pages(). Could you find another way ? Hmm. memcg uses per-cpu counters for counting event of alloc/free and trigger threashold check per 128 event on a cpu. Thanks, -Kame > --- > include/linux/mm.h | 15 +++++++++++++++ > mm/Kconfig | 8 ++++++++ > mm/page_alloc.c | 31 +++++++++++++++++++++++++++++++ > 3 files changed, 54 insertions(+), 0 deletions(-) > > diff --git a/include/linux/mm.h b/include/linux/mm.h index > 3dc3a8c..d133f73 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -1618,6 +1618,21 @@ extern int soft_offline_page(struct page *page, > int flags); > > extern void dump_page(struct page *page); > > +#ifdef CONFIG_MM_ALLOC_FREE_HOOK > +/* > + * Hook function type which called when some pages allocated or released. > + * Value of nr_pages is positive for post-allocation calls and > +negative > + * after free. > + */ > +typedef void (*mm_alloc_free_hook_t)(int nr_pages); > + > +/* > + * Setups specified hook function for tracking pages allocation. > + * Returns value of old hook to organize chains of calls if necessary. > + */ > +mm_alloc_free_hook_t set_mm_alloc_free_hook(mm_alloc_free_hook_t > +hook); #endif > + > #if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_HUGETLBFS) > extern void clear_huge_page(struct page *page, > unsigned long addr, > diff --git a/mm/Kconfig b/mm/Kconfig > index 011b110..2aaa1e9 100644 > --- a/mm/Kconfig > +++ b/mm/Kconfig > @@ -373,3 +373,11 @@ config CLEANCACHE > in a negligible performance hit. > > If unsure, say Y to enable cleancache > + > +config MM_ALLOC_FREE_HOOK > + bool "Enable callback support for pages allocation and releasing" > + default n > + help > + Required for some features like used memory meter. > + If unsure, say N to disable alloc/free hook. > + > diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 9dd443d..9307800 > 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -236,6 +236,30 @@ static void set_pageblock_migratetype(struct page > *page, int migratetype) > > bool oom_killer_disabled __read_mostly; > > +#ifdef CONFIG_MM_ALLOC_FREE_HOOK > +static atomic_long_t alloc_free_hook __read_mostly = > +ATOMIC_LONG_INIT(0); > + > +mm_alloc_free_hook_t set_mm_alloc_free_hook(mm_alloc_free_hook_t > +hook) { > + const mm_alloc_free_hook_t old_hook = > + (mm_alloc_free_hook_t)atomic_long_read(&alloc_free_hook); > + > + atomic_long_set(&alloc_free_hook, (long)hook); > + pr_info("MM alloc/free hook set to 0x%p (was 0x%p)\n", hook, > +old_hook); > + > + return old_hook; > +} > +EXPORT_SYMBOL(set_mm_alloc_free_hook); > + > +static inline void call_alloc_free_hook(int pages) { > + const mm_alloc_free_hook_t hook = > + (mm_alloc_free_hook_t)atomic_long_read(&alloc_free_hook); > + if (hook) > + hook(pages); > +} > +#endif > + > #ifdef CONFIG_DEBUG_VM > static int page_outside_zone_boundaries(struct zone *zone, struct > page *page) { @@ -2298,6 +2322,10 @@ __alloc_pages_nodemask(gfp_t > gfp_mask, unsigned int order, > put_mems_allowed(); > > trace_mm_page_alloc(page, order, gfp_mask, migratetype); > +#ifdef CONFIG_MM_ALLOC_FREE_HOOK > + call_alloc_free_hook(1 << order); > +#endif > + > return page; > } > EXPORT_SYMBOL(__alloc_pages_nodemask); > @@ -2345,6 +2373,9 @@ void __free_pages(struct page *page, unsigned int order) > free_hot_cold_page(page, 0); > else > __free_pages_ok(page, order); > +#ifdef CONFIG_MM_ALLOC_FREE_HOOK > + call_alloc_free_hook(-(1 << order)); #endif > } > } > > -- > 1.7.7.3 > > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href