From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 11B013A71AF for ; Wed, 13 May 2026 12:03:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778673790; cv=none; b=K1/5+GjdJqnGEVS5PKOCwozabdO9d4i9yjYgETG2cQsdazXmOvqGUA57JpZz0KP/VLmRdR6Uj4nawpiIYCIA120rQjwHuM0kAXcjUOXvOPEe01zWEFgbVAyNnmmLBKtPW/0lFTINbPHiHxSMPJ/JlrrRgz4eVWme5AlTeTgEvCg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778673790; c=relaxed/simple; bh=n/O1raLQ6SngGUgPEvI+NmfMMgn57+Y/s9CZdXppV1c=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=YjpXO+hN/SHFnAYEIOgpfSKgr4QIYSxvpXoLjqMeyuZfIQ6Pn7zeWpYNEpgFm1mZwSZX3gqQrYWoZ79Srau3O2XbYuQ2uh2aEAkf0NUnv4UIZQQoIT+leuk7Eobf89nNDnhoG+YRTC4YRdJ8tOFABtbgOLPSX/91xw7svOezNUU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=OLNGWdLs; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="OLNGWdLs" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8D846C2BCB7; Wed, 13 May 2026 12:03:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778673789; bh=n/O1raLQ6SngGUgPEvI+NmfMMgn57+Y/s9CZdXppV1c=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=OLNGWdLsl+8daqIqj/gVogNFsR5uV4P2oTh5FBsynOaeJp6gNSbShZEhIKEfhN2Ze 6IBCLP0kw3w7gENyk0qskkXt7KBQ8hmYejH0mOekxT6sUyO6BKPu4FQrgIpC4qSOqi ZOgUKErd5dEtsLOl1PkUtwU6IJncB8QimNGCIZ8Zc5tuEWYiUJ3UQiguykf7eonyI8 B7szlH+WVgLUCqdYXNfL5sZCGDC6gQOvSDkoft4kx6DODMvnHWyqrIReYo/R8o8ak5 BFnG9rl2Mqmzx4u+liykh052aEcJy3WeDHjRwqUrEIfH25wjww49cnbR69pUfH9kkt 2Youvf6gOLRMA== Message-ID: Date: Wed, 13 May 2026 14:03:05 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 1/5] mm/rmap: add tracepoint for rmap_walk To: xu.xin16@zte.com.cn, akpm@linux-foundation.org, ljs@kernel.org Cc: hughd@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, michel@lespinasse.org References: <20260503203911259NKHEr5gDy3PbvnSc077a7@zte.com.cn> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 5/3/26 14:39, xu.xin16@zte.com.cn wrote: > From: xu xin > > Add a new tracepoint rmap_walk in mm/rmap.c to monitor reverse mapping > traversal. The tracepoint records the duration (in nanoseconds), the > type of the folio (KSM, anonymous, or file-backed), and the addresses > of the folio and rmap_walk_control structures. The type determination > is performed inside the tracepoint to keep the function itself > lightweight. > > '# cat /sys/kernel/tracing/trace > '# tracer: nop > '# > '# entries-in-buffer/entries-written: 408/408 #P:4 > '# > '# _-----=> irqs-off/BH-disabled > '# / _----=> need-resched > '# | / _---=> hardirq/softirq > '# || / _--=> preempt-depth > '# ||| / _-=> migrate-disable > '# |||| / delay > '#TASK-PID CPU# ||||| TIMESTAMP FUNCTION > '# | | | ||||| | | > rmap-215 [001] ..... 692.237079: rmap_walk: folio=000000000029ddcb rwc=00000000dac4cda0 duration_ns=828682 page_type=ksm locked=false > rmap-215 [001] ..... 692.239480: rmap_walk: folio=0000000092a21fd3 rwc=00000000986376ff duration_ns=905966 page_type=ksm locked=false > rmap-230 [003] ..... 692.583619: rmap_walk: folio=0000000037a237b6 rwc=0000000080fbbb0a duration_ns=107892 page_type=ksm locked=false > rmap-230 [003] ..... 692.584104: rmap_walk: folio=0000000031bdbf8b rwc=00000000b39c973a duration_ns=330886 page_type=ksm locked=false > rmap-244 [003] ..... 692.708706: rmap_walk: folio=000000009105fa6b rwc=0000000037d46cd7 duration_ns=987826 page_type=file locked=false > rmap-244 [003] ..... 692.709198: rmap_walk: folio=000000009105fa6b rwc=0000000093942e2c duration_ns=161733 page_type=file locked=false > rmap-244 [003] ..... 692.709606: rmap_walk: folio=000000009105fa6b rwc=0000000037d46cd7 duration_ns=54428 page_type=file locked=false > rmap-244 [003] ..... 692.709658: rmap_walk: folio=000000009105fa6b rwc=0000000093942e2c duration_ns=27192 page_type=file locked=false > > Signed-off-by: xu xin > --- > include/trace/events/rmap.h | 49 +++++++++++++++++++++++++++++++++++++ > mm/rmap.c | 14 +++++++++++ > 2 files changed, 63 insertions(+) > create mode 100644 include/trace/events/rmap.h > > diff --git a/include/trace/events/rmap.h b/include/trace/events/rmap.h > new file mode 100644 > index 000000000000..987fa204d65d > --- /dev/null > +++ b/include/trace/events/rmap.h > @@ -0,0 +1,49 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +#undef TRACE_SYSTEM > +#define TRACE_SYSTEM rmap > + > +#if !defined(_TRACE_RMAP_H) || defined(TRACE_HEADER_MULTI_READ) > +#define _TRACE_RMAP_H > + > +#include > +#include > + > +#define GET_RMAP_PAGE_TYPE(folio) (folio_test_ksm(folio) ? "ksm" : \ > + (folio_test_anon(folio) ? "anon" : "file")) > + > +TRACE_EVENT(rmap_walk, > + > + TP_PROTO(struct folio *folio, struct rmap_walk_control *rwc, u64 duration_ns, bool locked), > + > + TP_ARGS(folio, rwc, duration_ns, locked), > + > + TP_STRUCT__entry( > + __field(unsigned long, folio_addr) > + __field(unsigned long, rwc_addr) > + __field(u64, duration_ns) > + __string(page_type, GET_RMAP_PAGE_TYPE(folio)) > + __field(bool, locked) > + ), > + > + TP_fast_assign( > + __entry->folio_addr = (unsigned long)folio; > + __entry->rwc_addr = (unsigned long)rwc; > + __entry->duration_ns = duration_ns; > + __assign_str(page_type); > + __entry->locked = locked; > + ), > + > + TP_printk("folio=%p rwc=%p duration_ns=%llu page_type=%s locked=%s", > + (void *)(unsigned long)__entry->folio_addr, > + (void *)(unsigned long)__entry->rwc_addr, > + __entry->duration_ns, > + __get_str(page_type), > + __entry->locked ? "true" : "false") > +); > + > + > + > +#endif /* _TRACE_RMAP_H */ > + > +/* This part must be outside protection */ > +#include > diff --git a/mm/rmap.c b/mm/rmap.c > index 78b7fb5f367c..14bf8483f38b 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -75,11 +75,13 @@ > #include > #include > #include > +#include > > #include > > #define CREATE_TRACE_POINTS > #include > +#include > > #include "internal.h" > #include "swap.h" > @@ -3098,23 +3100,35 @@ static void rmap_walk_file(struct folio *folio, > > void rmap_walk(struct folio *folio, struct rmap_walk_control *rwc) > { > + u64 ts_start, delta_ns; > + ts_start = local_clock(); > + > if (unlikely(folio_test_ksm(folio))) > rmap_walk_ksm(folio, rwc); > else if (folio_test_anon(folio)) > rmap_walk_anon(folio, rwc, false); > else > rmap_walk_file(folio, rwc, false); > + > + delta_ns = local_clock() - ts_start; > + trace_rmap_walk(folio, rwc, delta_ns, false); > } > > /* Like rmap_walk, but caller holds relevant rmap lock */ > void rmap_walk_locked(struct folio *folio, struct rmap_walk_control *rwc) > { > + u64 ts_start, delta_ns; > + ts_start = local_clock(); > + > /* no ksm support for now */ > VM_BUG_ON_FOLIO(folio_test_ksm(folio), folio); > if (folio_test_anon(folio)) > rmap_walk_anon(folio, rwc, true); > else > rmap_walk_file(folio, rwc, true); > + > + delta_ns = local_clock() - ts_start; > + trace_rmap_walk(folio, rwc, delta_ns, true); > } > > #ifdef CONFIG_HUGETLB_PAGE Doing the clock stuff manually is nasty. We could have a trace_rmap_walk_start() + trace_rmap_walk_stop(). But I wonder right now, whether we really need that information in the tree? For local debugging (what you did) having this OOT patch is probably fine. -- Cheers, David