From: "David Hildenbrand (Arm)" <david@kernel.org>
To: xu.xin16@zte.com.cn, akpm@linux-foundation.org
Cc: chengming.zhou@linux.dev, hughd@google.com,
wang.yaxin@zte.com.cn, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, ljs@kernel.org, corbet@lwn.net
Subject: Re: [PATCH v7 1/6] mm/rmap: add tracepoint for rmap_walk
Date: Fri, 5 Jun 2026 17:53:19 +0200 [thread overview]
Message-ID: <041ba9b4-305e-49b1-affd-079fe4220e48@kernel.org> (raw)
In-Reply-To: <202605301703094695zmVgcSC27BNR0rH0N8_x@zte.com.cn>
On 5/30/26 11:03, xu.xin16@zte.com.cn wrote:
> From: xu xin <xu.xin16@zte.com.cn>
>
> Add trace_rmap_walk_start() and trace_rmap_walk_end() to bracket
> reverse mapping walks. Unlike manual clock sampling, these
> tracepoints record no timestamp; latency can be computed offline
> by tools (e.g., perf, trace-cmd) using the event timestamps.
>
> When tracepoints are disabled, the only cost is a static branch
> check (no clock read, no duration calculation), making them
> suitable for production use.
>
> The information (folio type, locked state) helps diagnose
> performance issues in KSM, anonymous, and file-backed rmap walks.
>
> Signed-off-by: xu xin <xu.xin16@zte.com.cn>
> ---
Learning that trace events can easily become stable ABI, we should consider
dropping this patch or switching to DECLARE_TRACE().
See Steve's explanation:
https://lore.kernel.org/r/20260603130006.7d2c4a62@gandalf.local.home
I assume this could be carried as an OOT patch when really working debugging
scenarios?
--
Cheers,
David
next prev parent reply other threads:[~2026-06-05 15:53 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-30 8:59 [PATCH v7 0/6] KSM: performance optimizations for rmap_walk_ksm xu.xin16
2026-05-30 9:03 ` [PATCH v7 1/6] mm/rmap: add tracepoint for rmap_walk xu.xin16
2026-06-05 15:53 ` David Hildenbrand (Arm) [this message]
2026-05-30 9:04 ` [PATCH v7 2/6] tools/testing: add rmap walk latency benchmark xu.xin16
2026-06-05 15:54 ` David Hildenbrand (Arm)
2026-05-30 9:06 ` [PATCH v7 3/6] MAINTAINERS: add myself as reviewer for rmap section xu.xin16
2026-06-05 16:03 ` David Hildenbrand (Arm)
2026-06-05 16:16 ` Lorenzo Stoakes
2026-05-30 9:07 ` [PATCH v7 4/6] ksm: add pgoff into ksm_rmap_item xu.xin16
2026-06-05 17:19 ` David Hildenbrand (Arm)
2026-06-09 4:51 ` xu.xin16
2026-05-30 9:09 ` [PATCH v7 5/6] ksm: Optimize rmap_walk_ksm by passing a suitable pgoff xu.xin16
2026-05-30 9:10 ` [PATCH v7 6/6] ksm: add mremap selftests for ksm_rmap_walk xu.xin16
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