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b=OLNGWdLsl+8daqIqj/gVogNFsR5uV4P2oTh5FBsynOaeJp6gNSbShZEhIKEfhN2Ze 6IBCLP0kw3w7gENyk0qskkXt7KBQ8hmYejH0mOekxT6sUyO6BKPu4FQrgIpC4qSOqi ZOgUKErd5dEtsLOl1PkUtwU6IJncB8QimNGCIZ8Zc5tuEWYiUJ3UQiguykf7eonyI8 B7szlH+WVgLUCqdYXNfL5sZCGDC6gQOvSDkoft4kx6DODMvnHWyqrIReYo/R8o8ak5 BFnG9rl2Mqmzx4u+liykh052aEcJy3WeDHjRwqUrEIfH25wjww49cnbR69pUfH9kkt 2Youvf6gOLRMA== Message-ID: Date: Wed, 13 May 2026 14:03:05 +0200 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; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20260503203911259NKHEr5gDy3PbvnSc077a7@zte.com.cn> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: BA82710001E X-Stat-Signature: ejtfbkjixafmzdfzwapp79838z3hdoj1 X-Rspam-User: X-HE-Tag: 1778673790-522613 X-HE-Meta: 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 yynD8omw MvprRkzTHXBNXbH7hGOeD27ur96EaY1XILUAG7z+5i6E8pgJAd3rU6P9He6gTVzNP/7CKBWyDmhNtR0Tzsc8kXF8vWiPjDCHb0C50820cKpbB0Y+cJwz+pWAJ8B0p80X+jFYusV9crNCSyeMCPNhuysUbb0BgKzQ7TeBja0g63daGvZb+IFIqKzzyqSIDMZEUhUNQ5Tk8WM4aoYJfMCiHNSDVbvOzTYm1VVzYpaiUi8LWtykMWK5F5aHThksQIkZ0FqNlowHJAhVue0xFJHFDiOhhuOURqJu3eJN44SpFlL3QsamLLqUjGcCnvdf2htFm36g+b4yn3FakRewHVd4pigr0APsMIwPqF5UvZfT7VSQjCX0= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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