linux-kernel - Re: [Patch v2] [PATCH] mm/page_alloc: Fix tracepoint mm_page_alloc_zone

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Date:   Tue, 24 May 2022 21:22:00 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Wonhyuk Yang <vvghjk1234@...il.com>
Cc:     Mel Gorman <mgorman@...e.de>, Ingo Molnar <mingo@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Baik Song An <bsahn@...i.re.kr>,
        Hong Yeon Kim <kimhy@...i.re.kr>,
        Taeung Song <taeung@...llinux.co.kr>, linuxgeek@...uxgeek.io,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [Patch v2] [PATCH] mm/page_alloc: Fix tracepoint
 mm_page_alloc_zone_locked()

Sorry for the late reply, but I finally have time to catchup on my inbox.

On Thu, 12 May 2022 11:53:07 +0900
Wonhyuk Yang <vvghjk1234@...il.com> wrote:

> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -2476,6 +2476,9 @@ struct page *__rmqueue_smallest(struct zone *zone, unsigned int order,
>  		del_page_from_free_list(page, zone, current_order);
>  		expand(zone, page, order, current_order, migratetype);
>  		set_pcppage_migratetype(page, migratetype);
> +		trace_mm_page_alloc_zone_locked(page, order, migratetype, 
> +				pcp_allowed_order(order) &&
> +				migratetype < MIGRATE_PCPTYPES);

It would make more sense to put this logic into the TP_fast_assign() if
possible. This code is added at the location of execution, and even though
it may not run while tracing is disabled, it does affect icache.

Could you pass in the order (you already have migratetype) and then in the
trace event have:


 	TP_fast_assign(
 		__entry->pfn		= page ? page_to_pfn(page) : -1UL;
 		__entry->order		= order;
 		__entry->migratetype	= migratetype;
+		__entry->percpu_refill	= pcp_allowed_order(order) &&
					  migratetype < MIGRATE_PCPTYPES);
 	),

??

-- Steve

>  		return page;
>  	}
>