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[23.116.43.216]) by smtp.gmail.com with ESMTPSA id 956f58d0204a3-65e0d86bc02sm4342876d50.4.2026.05.16.14.04.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 16 May 2026 14:04:07 -0700 (PDT) From: Ravi Jonnalagadda To: sj@kernel.org, damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org Cc: akpm@linux-foundation.org, corbet@lwn.net, bijan311@gmail.com, ajayjoshi@micron.com, honggyu.kim@sk.com, yunjeong.mun@sk.com, ravis.opensrc@gmail.com Subject: [RFC PATCH 3/5] mm/damon/core: floor effective quota size at minimum region size Date: Sat, 16 May 2026 14:03:55 -0700 Message-ID: <20260516210357.2247-4-ravis.opensrc@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260516210357.2247-1-ravis.opensrc@gmail.com> References: <20260516210357.2247-1-ravis.opensrc@gmail.com> Precedence: bulk X-Mailing-List: damon@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The CONSIST quota goal tuner initializes esz_bp to 0, producing an effective quota size (esz) of 1 byte on the first tick. damos_quota_is_full() rejects all regions when esz < min_region_sz (default PAGE_SIZE = 4096), so no regions can be tried and no feedback reaches the tuner — a bootstrapping deadlock. Floor esz at ctx->min_region_sz after the tuner computes it, guarded by an esz != 0 check. The guard preserves the temporal tuner's intentional stop behavior: when score >= 10000 (goal met), temporal sets esz_bp = 0 to halt migration; the floor must not override that. Signed-off-by: Ravi Jonnalagadda --- mm/damon/core.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/mm/damon/core.c b/mm/damon/core.c index fd1db234ca304..d33c4360cbd60 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -2650,6 +2650,10 @@ static void damos_set_effective_quota(struct damon_ctx *ctx, struct damos *s) esz = quota->esz_bp / 10000; } + /* avoid cold-start deadlock, but respect tuner stop signal (esz=0) */ + if (esz) + esz = max_t(unsigned long, esz, ctx->min_region_sz); + if (quota->ms) { if (quota->total_charged_ns) throughput = mult_frac(quota->total_charged_sz, -- 2.43.0