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Mon, 03 Mar 2025 02:06:30 -0800 (PST) From: Tang Yizhou X-Google-Original-From: Tang Yizhou To: tj@kernel.org, jack@suse.cz, brauner@kernel.org, willy@infradead.org, akpm@linux-foundation.org Cc: rostedt@goodmis.org, mhiramat@kernel.org, ast@kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Tang Yizhou Subject: [PATCH RESEND 2/2] writeback: Fix calculations in trace_balance_dirty_pages() for cgwb Date: Mon, 3 Mar 2025 18:06:17 +0800 Message-Id: <20250303100617.223677-3-yizhou.tang@shopee.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20250303100617.223677-1-yizhou.tang@shopee.com> References: <20250303100617.223677-1-yizhou.tang@shopee.com> MIME-Version: 1.0 X-Stat-Signature: a8t53p6xzftpx3wp6s1xy33x778kndpm X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 55C85160002 X-Rspam-User: X-HE-Tag: 1740996392-91388 X-HE-Meta: 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 wFgEk/Yg GwWedSgBRyS+6KUbgNInZpAnRlEjp8dDQnduzPR56B+UA5CqOY/gi/KmdGhkOhtsA0y+W5miCjGQcdQ9BBr1eUw8plFszYpE/rYRdsLjGi0KRrf6I6r5tg/G/z438kHx42g/C8zTp//8R+YRf01pwP8+v5YbQcuwH+9BCAxf/pu2W9bZcugFFbhZFLLDGwgxZJsM4CZxvLQ8O2fqiQArkdEZt828v8gIYYzT2eSY6L6UyztXwQL+sb4f+ydVRz2FBZLs+LhxO7MuPIkAWkecK/jmGUw1I8tdQRRI8AQ3tpz++EEVosjz1d6mq68FQbFiLl9pz0qv/3cuWEf+Cn+GxAfaIDMkwSzaJeBb+1NNrQ5bSiZrbrat3JYwAHkUgtew17LXY X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Tang Yizhou In the commit dcc25ae76eb7 ("writeback: move global_dirty_limit into wb_domain") of the cgroup writeback backpressure propagation patchset, Tejun made some adaptations to trace_balance_dirty_pages() for cgroup writeback. However, this adaptation was incomplete and Tejun missed further adaptation in the subsequent patches. In the cgroup writeback scenario, if sdtc in balance_dirty_pages() is assigned to mdtc, then upon entering trace_balance_dirty_pages(), __entry->limit should be assigned based on the dirty_limit of the corresponding memcg's wb_domain, rather than global_wb_domain. To address this issue and simplify the implementation, introduce a 'limit' field in struct dirty_throttle_control to store the hard_limit value computed in wb_position_ratio() by calling hard_dirty_limit(). This field will then be used in trace_balance_dirty_pages() to assign the value to __entry->limit. Fixes: dcc25ae76eb7 ("writeback: move global_dirty_limit into wb_domain") Signed-off-by: Tang Yizhou --- include/linux/writeback.h | 1 + include/trace/events/writeback.h | 5 ++--- mm/page-writeback.c | 2 +- 3 files changed, 4 insertions(+), 4 deletions(-) diff --git a/include/linux/writeback.h b/include/linux/writeback.h index 32095928365c..58bda3347914 100644 --- a/include/linux/writeback.h +++ b/include/linux/writeback.h @@ -326,6 +326,7 @@ struct dirty_throttle_control { unsigned long dirty; /* file_dirty + write + nfs */ unsigned long thresh; /* dirty threshold */ unsigned long bg_thresh; /* dirty background threshold */ + unsigned long limit; /* hard dirty limit */ unsigned long wb_dirty; /* per-wb counterparts */ unsigned long wb_thresh; diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h index 3046ca6b08ea..0ff388131fc9 100644 --- a/include/trace/events/writeback.h +++ b/include/trace/events/writeback.h @@ -663,9 +663,8 @@ TRACE_EVENT(balance_dirty_pages, unsigned long freerun = (dtc->thresh + dtc->bg_thresh) / 2; strscpy_pad(__entry->bdi, bdi_dev_name(wb->bdi), 32); - __entry->limit = global_wb_domain.dirty_limit; - __entry->setpoint = (global_wb_domain.dirty_limit + - freerun) / 2; + __entry->limit = dtc->limit; + __entry->setpoint = (dtc->limit + freerun) / 2; __entry->dirty = dtc->dirty; __entry->wb_setpoint = __entry->setpoint * dtc->wb_thresh / (dtc->thresh + 1); diff --git a/mm/page-writeback.c b/mm/page-writeback.c index e980b2aec352..3147119a9a04 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -1072,7 +1072,7 @@ static void wb_position_ratio(struct dirty_throttle_control *dtc) struct bdi_writeback *wb = dtc->wb; unsigned long write_bw = READ_ONCE(wb->avg_write_bandwidth); unsigned long freerun = dirty_freerun_ceiling(dtc->thresh, dtc->bg_thresh); - unsigned long limit = hard_dirty_limit(dtc_dom(dtc), dtc->thresh); + unsigned long limit = dtc->limit = hard_dirty_limit(dtc_dom(dtc), dtc->thresh); unsigned long wb_thresh = dtc->wb_thresh; unsigned long x_intercept; unsigned long setpoint; /* dirty pages' target balance point */