From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta0.migadu.com (out-217.mta0.migadu.com [91.218.175.217]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B4FE3347C6 for ; Mon, 19 Oct 2026 03:45:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.217 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792381548; cv=none; b=YVwreHv4bWQA0WvXO3eJOW+0Xb+WHauIKz+o9QAfMM1jNg3IMkcg9CnGrPTuRlJdM/BmD81lMN4xhQnWaV+msaHoqfUdeCL+wb2c80oZd0hx5HkJvFnoV6Hv9ofgwgrBU3eW40aRl+fSsvVyh8D83I/WP3IP0QOGQXby0G9Jnyg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792381548; c=relaxed/simple; bh=GVmvFdM+XNAIwjgACYtP3IWMZfKPh9cvSBz2M6fBa94=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=c8HzJ2kXgAW4ea/xTa9jVHw+SSJdffzhRpT9uyEO/veW6X+K5sD/i3hfrxBJzIcuYxiqxVXAlWGWY0CLqIAF9O6K8eszsl6BeH6MOaGYW1ZkK/532JG7iBP2t6rTP/JlOJ0GGgE9BUowrRD7KJzznjFU5Y1kkEHE3JcVQFeie1A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=ZpR3aEjO; arc=none smtp.client-ip=91.218.175.217 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="ZpR3aEjO" X-Envelope-To: linux-trace-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=GVmvFdM+XNAIwjgACYtP3IWMZfKPh9cvSBz2M6fBa94=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1792381544; v=1; x=1792986344; b=ZpR3aEjOfsVXgDki7RQvm55pc+bhVSFtt9iPrfFyfF/idDY8TvsLYU2gAV8vAdX8HGJWRyFm PbmAg/h7i5S7VQR8M4MWs81LU1kceXOXv2O17BKxQD5UlubU8PjLrk1AnPeg4MOt7j3wziJFtAo nQZBKG6OA+SAS8Q8HW4Cg3dU= X-Envelope-To: linux-trace-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id d6fb5d35c48fecbe; Mon, 19 Oct 2026 03:45:38 +0000 X-Mizu-Trace-ID: d6fb5d35c48fecbe X-Migadu-Flow: FLOW_OUT From: Ridong Chen To: Steven Rostedt , Masami Hiramatsu , Andrew Morton , Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Dave Chinner Cc: Mathieu Desnoyers , Muchun Song , Qi Zheng , David Hildenbrand , Lorenzo Stoakes , Kairui Song , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Baoquan He , Baolin Wang , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org (open list:CONTROL GROUP - MEMORY RESOURCE CONTROLLER (MEMCG)), bpf@vger.kernel.org (open list:BPF [MISC]:Keyword:(?:\b|_)bpf(?:\b|_)), Ridong Chen , Ridong Chen Subject: [PATCH v4 0/9] mm/vmscan: move tracepoints to mm/ and add MGLRU tracepoints Date: Mon, 19 Oct 2026 11:44:17 +0800 Message-Id: <20261019034426.2354049-1-ridong.chen@linux.dev> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Ridong Chen Background ========== MGLRU currently has no tracepoints of its own. The scan and evict paths reuse the classic-LRU tracepoints (trace_mm_vmscan_lru_isolate() and trace_mm_vmscan_lru_shrink_inactive()), which predate MGLRU and carry no generation, sequence or memcg context. A trace of a running system therefore cannot tell which memcg a given scan belongs to, how far reclaim has progressed through the generations, or when a new generation is created. While reviewing an earlier version that added two MGLRU tracepoints, Steven suggested moving include/trace/events/vmscan.h to mm/trace_vmscan.h [1], as several other subsystems already do. Once the header lives under mm/, struct scan_control can be moved there too, letting the trace events access its fields directly instead of having each callsite copy the scalars out by hand. This version merges the two efforts into one series: the restructuring first, then the two new tracepoints built on top of it. Implementation ============== Part 1, restructuring (patches 1-7): 1) drop the unused vmscan trace include from memcontrol.c; 2) move include/trace/events/vmscan.h to mm/trace_vmscan.h, setting TRACE_INCLUDE_PATH to "." and adding -I$(src) for vmscan.o; 3) move struct scan_control into a dedicated mm/vmscan.h with an ordinary include guard, which trace_vmscan.h pulls in; 4-7) pass scan_control to the vmscan tracepoints and pick the fields out in TP_fast_assign, one group at a time: the reclaim-begin events, the LRU isolate/shrink events, mm_vmscan_reclaim_pages and mm_vmscan_balance_pgdat_end. Part 2, MGLRU tracepoints (patches 8-9): 8) add mm_mglru_scan_folios on the scan path, next to the classic mm_vmscan_lru_isolate, reporting the same counters plus nr_sorted and the nid, memcg id, max_seq, tier and min_seq of the lruvec; 9) add mm_mglru_inc_max_seq on the aging path, reporting the nid, memcg id, the new max_seq, the anon/file min_seq and the per-generation page counts of both types. Both new events only take pointers (lruvec, sc) plus the local counters, and derive everything else in TP_fast_assign(), so the reclaim paths do no extra work when they are disabled. Effect ====== Part 1 moves the loads of the tracepoint arguments out of the reclaim paths and into the trace event callbacks, which only run when the event is enabled. On x86_64 with gcc 11.4, the callers in mm/vmscan.o shrink accordingly (bytes), e.g.: isolate_lru_folios 4060 -> 3896 (-164) __node_reclaim 2407 -> 2225 (-182) isolate_folios 8706 -> 8577 (-129) shrink_active_list 3674 -> 3549 (-125) evict_folios 4858 -> 4769 (-89) There is no functional change in part 1. TP_STRUCT__entry and TP_printk of the existing events are untouched, so their tracefs format is identical. This was confirmed by diffing the tracefs format files before and after, and by capturing the direct/memcg/node reclaim-begin events under load in a QEMU guest (order, gfp_flags and memcg_id all match). BPF programs attached via raw_tp/tp_btf do see the new TP_PROTO and need to be adjusted; tracepoints are not a stable ABI (see Documentation/bpf/bpf_design_QA.rst). highest_zoneidx and nr_reclaimed stay separate arguments: the former is a balance_pgdat() parameter (sc.reclaim_idx may differ from it by the time the end event fires), and the latter is the return value of shrink_folio_list(), which does not update sc->nr_reclaimed. Part 2 makes the full aging-to-eviction window observable per memcg: aging advances max_seq (the leading edge), scanning consumes the oldest generations, and the min_seq/max_seq pair on each event shows how the generation window moves over time. A sample trace, with the classic-LRU tracepoints left enabled to show how they interleave: mm_vmscan_lru_isolate: classzone=4 order=0 nr_requested=4 nr_scanned=1 nr_skipped=0 nr_taken=1 lru=inactive_file mm_mglru_scan_folios: nid=0 memcg_id=1833 classzone=4 order=0 nr_requested=4 nr_scanned=1 nr_sorted=0 nr_skipped=0 nr_taken=1 lru=inactive_file max_seq=3 tier=3 min_seq=0 mm_vmscan_lru_shrink_inactive: nid=0 nr_scanned=1 nr_reclaimed=1 nr_dirty=0 nr_writeback=0 nr_congested=0 nr_immediate=0 nr_activate_anon=0 nr_activate_file=0 nr_ref_keep=0 nr_unmap_fail=0 priority=2 flags=RECLAIM_WB_FILE|RECLAIM_WB_ASYNC mm_mglru_inc_max_seq: nid=0 memcg_id=1833 max_seq=4 anon_min_seq=1 file_min_seq=1 nr_anon={0x0,0x0,0x0,0x0} nr_file={0x0,0x12,0x0,0x0} mm_vmscan_lru_isolate: classzone=4 order=0 nr_requested=3 nr_scanned=3 nr_skipped=0 nr_taken=3 lru=inactive_file mm_mglru_scan_folios: nid=0 memcg_id=1833 classzone=4 order=0 nr_requested=3 nr_scanned=3 nr_sorted=0 nr_skipped=0 nr_taken=3 lru=inactive_file max_seq=4 tier=3 min_seq=1 mm_vmscan_lru_shrink_inactive: nid=0 nr_scanned=3 nr_reclaimed=3 nr_dirty=0 nr_writeback=0 nr_congested=0 nr_immediate=0 nr_activate_anon=0 nr_activate_file=0 nr_ref_keep=0 nr_unmap_fail=0 priority=2 flags=RECLAIM_WB_FILE|RECLAIM_WB_ASYNC The mm_mglru_scan_folios lines carry the node, memcg id and the generation window (max_seq/min_seq) that the bare mm_vmscan_lru_isolate lines above them cannot - those cannot even say which memcg they came from. The mm_mglru_inc_max_seq line then shows a new generation being created (max_seq 3 -> 4) with the per-generation page counts for both types, and the following scan already reports the moved window (max_seq=4 min_seq=1). [1]: https://lore.kernel.org/linux-mm/20260916095122.50cbb620@robin/ --- Changes in v4: - Merge the MGLRU tracepoint series [2] into this one, on top of the restructuring, and drop the RFC tag. - Patch 2: use TRACE_INCLUDE_PATH "." with CFLAGS_vmscan.o += -I$(src) instead of a relative path (Steven). - Patches 8-9: pass lruvec/sc and compute the fields in TP_fast_assign() instead of at the call site (Steven). - Patches 8-9: add nid, derived from the lruvec (Baoquan). - Patch 8: group the int fields at the end of the entry to avoid padding on 64-bit (Steven). - Drop "mm/mglru: factor out lru_gen_seq_nr_pages()" from [2]: the per-generation page count is now summed inside TP_fast_assign(), so the helper has no user. The Reviewed-by tags given to [2] are not carried over, as patches 8-9 changed substantially. - Link to RFC v3: https://lore.kernel.org/all/20261013131309.2790253-1-ridong.chen@linux.dev/ Changes in RFC v3: - Use "Assisted-by: LLM" (Muchun). - Note the BPF raw_tp/tp_btf impact in the changelogs (Sashiko). - Changelog wording fixes and minor indentation fixes. - Link to RFC v2: https://lore.kernel.org/all/20260928114625.3609130-1-ridong.chen@linux.dev/ Changes in RFC v2: - Convert the remaining vmscan tracepoints too. - Move struct scan_control to mm/vmscan.h (Baoquan). [2]: https://lore.kernel.org/all/20260911102939.2485750-1-ridong.chen@linux.dev/ Ridong Chen (9): mm/memcontrol: drop unused vmscan tracepoint include mm/vmscan: move vmscan tracepoints to a local header mm/vmscan: move struct scan_control to a dedicated header mm/vmscan: pass scan_control to the reclaim-begin tracepoints mm/vmscan: pass scan_control to the LRU isolate/shrink tracepoints mm/vmscan: pass scan_control to mm_vmscan_reclaim_pages mm/vmscan: pass scan_control to mm_vmscan_balance_pgdat_end mm/mglru: add tracepoint for scan_folios() mm/mglru: add tracepoint for inc_max_seq() MAINTAINERS | 4 + mm/Makefile | 1 + mm/memcontrol.c | 2 - mm/shrinker.c | 2 +- .../events/vmscan.h => mm/trace_vmscan.h | 193 ++++++++++++++---- mm/vmscan.c | 140 ++----------- mm/vmscan.h | 118 +++++++++++ 7 files changed, 296 insertions(+), 164 deletions(-) rename include/trace/events/vmscan.h => mm/trace_vmscan.h (76%) create mode 100644 mm/vmscan.h base-commit: 48fe11c8d0f1e4e59426a3606f20ac1130b6d8dc -- 2.34.1