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From: Shakeel Butt To: Bunyod Suvonov Cc: akpm@linux-foundation.org, hannes@cmpxchg.org, rostedt@goodmis.org, mhiramat@kernel.org, david@kernel.org, mhocko@kernel.org, zhengqi.arch@bytedance.com, ljs@kernel.org, mathieu.desnoyers@efficios.com, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/vmscan: add balance_pgdat begin/end tracepoints Message-ID: References: <20260423103753.546582-1-b.suvonov@sjtu.edu.cn> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260423103753.546582-1-b.suvonov@sjtu.edu.cn> X-Migadu-Flow: FLOW_OUT X-Stat-Signature: 1ff3pgcwjg5yc6i1yeb53efmdn4u7m66 X-Rspamd-Queue-Id: EB3FB14000F X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1776966422-718457 X-HE-Meta: U2FsdGVkX19UJwO8q/PvuEmQ0WYtSHPPR1uW+nlTgHQXiIOwhGGHX9OCWa2rVDQgWpBwQy/DG273xfudY7OlMP3shzeJeWq6c9PsIros0QAPJq+ZRAdS/m2Wdt7CsxGz7VuPi6Lr263bd1BmxLEYGwMSmRMt1ycLD//0KJkddF71Fl4yZdYdX2veRHRBfQaD2+S/hKvJGTxN23E9kJ64sJIOmU/L3vtateUTUMSgqjfBPoscuyGHinDFjL3etnJObZ4b5ygOSXE2TgCm+jz7AyMN4YygTp0kgv9jPrZVky7m9otrXE+poWj324fOXsooy5P0UAwbMdPytwMSfKivh4MF0UVjP87gN7wK2e2EwTMKChIhjVbRY+sMUGKiZ/np7YVuH4C+0aQCC8bwEEgska/wmayGHwPXOJinsgzHtq/226c/H9dhNjJpx1dme7CxO9mVs3P9V9VxvYIf4ldOSp2b7yxe8MgXTYT+vV1Qnn6G25tNLP5EeFPMatNhNUuWOXURTkhVLfQfbFYq/vnm96XkHjQwVFVJpiEKN76bza/0tZx4EujYkJ91lPZ7JoBDcFykmJ234H5xIHXTBI67siTA8nTZQsmTmAS4Nb0lEj0wTLcS0GQr2YS642cXW3CDBmmMp0OlPBIVT51Cb0uae2qlYt/nQ9Q/YfDtG5HxJR0bI2NPssUxQGV4VncRa5ARhgWtA5v/5jsj3pJ0lkzr8q5BK873O6kEuPxsQaHf4k/XbvImfipC9ZeSZXOxQK3RDDq8M8kvrVhyV3HK4C9Os46QRqOGAhCqdjVJPp9PalMLRYUuDuSHqRt8Ov7W2q67JvdNqFPS60u55zGEyhfVIZn7MEE7aaUROhXQRLIbKXh8lwD7EqL6ikrkTiZLXdPdlBPy7F/j3fHfL3Ej7tn0CCR8oBQg0mBscv00d8QwOT0d2HKj41oZm4xwyq0uXdb9F9PtOVoSDW9YoSA5UMR uORl0z9V 0c89ZQiOqOf4PV+eXdxIOu0IiNNKo8h4DYW9cDmtUljKVeQMbYhAuaI5+cnvo8RjedGF9TE4rI0qrLBXdCujbnmPMbDPd4rTvJkXENCjVOzZCuZcOGdvYNID4R6zVwc9abqqkfKkWQUiCdoMcGYOfdByf0KJiIoyFtgxszJu+aEnAgGKESScxUp3D/Z4TabtYulAnC68agc2ZYqoq5T2Y2GLJPpQIO157DfcQZMb0uG4zyfU5ct+xy2Uk4eN3JIGZSdx8 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Apr 23, 2026 at 06:37:53PM +0800, Bunyod Suvonov wrote: > Vmscan has six main reclaim entry points: try_to_free_pages() for > direct reclaim, try_to_free_mem_cgroup_pages() for memcg reclaim, > mem_cgroup_shrink_node() for memcg soft limit reclaim, node_reclaim() > for node reclaim, shrink_all_memory() for hibernation reclaim, and > balance_pgdat() for kswapd reclaim. > > All of them, except for shrink_all_memory() and balance_pgdat(), already > have begin/end tracepoints. This makes it harder to trace which reclaim > path is responsible for memory reclaim activity, because kswapd reclaim > cannot be identified as cleanly as other reclaim entry points, even > though it is the main background reclaim path under memory pressure. > There may be no need to trace shrink_all_memory() as it is primarily > used during hibernation. So this patch adds the missing tracepoint pair > for balance_pgdat(). > > The begin tracepoint records the node id, requested reclaim order, and > highest_zoneidx. The end tracepoint records the node id, reclaim order > that balance_pgdat() finished with, highest_zoneidx, and nr_reclaimed. Do we need to trace highest_zoneidx at the end? Can it change within balance_pgdat()? > Together, they show the requested reclaim order and zone bound, whether > reclaim fell back to a lower order, and how much reclaim work was done. > > Signed-off-by: Bunyod Suvonov Overall looks good.