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[2603:7000:c01:2716:97cf:7b55:44af:acd6]) by smtp.gmail.com with ESMTPSA id k4-20020a05620a07e400b00783dc450d84sm16978qkk.12.2024.02.01.09.55.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 01 Feb 2024 09:55:37 -0800 (PST) Date: Thu, 1 Feb 2024 12:55:36 -0500 From: Johannes Weiner To: Chengming Zhou Cc: Nhat Pham , Andrew Morton , Yosry Ahmed , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 4/6] mm/zswap: remove duplicate_entry debug value Message-ID: <20240201175536.GD321148@cmpxchg.org> References: <20240201-b4-zswap-invalidate-entry-v1-0-56ed496b6e55@bytedance.com> <20240201-b4-zswap-invalidate-entry-v1-4-56ed496b6e55@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240201-b4-zswap-invalidate-entry-v1-4-56ed496b6e55@bytedance.com> X-Stat-Signature: 15gus37h9ogttt8hmgkb93r8t658d7ef X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 5B61040008 X-Rspam-User: X-HE-Tag: 1706810139-237427 X-HE-Meta: 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 e96+e1fT 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 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: On Thu, Feb 01, 2024 at 03:49:04PM +0000, Chengming Zhou wrote: > cat /sys/kernel/debug/zswap/duplicate_entry > 2086447 > > When testing, the duplicate_entry value is very high, but no warning > message in the kernel log. From the comment of duplicate_entry > "Duplicate store was encountered (rare)", it seems something goes wrong. > > Actually it's incremented in the beginning of zswap_store(), which found > its zswap entry has already on the tree. And this is a normal case, > since the folio could leave zswap entry on the tree after swapin, > later it's dirtied and swapout/zswap_store again, found its original > zswap entry. (Maybe we can reuse it instead of invalidating it?) Probably not worth it, especially after the next patch. > So duplicate_entry should be only incremented in the real bug case, > which already have "WARN_ON(1)", it looks redundant to count bug case, > so this patch just remove it. > > Signed-off-by: Chengming Zhou Either way, I agree that the WARN_ON() is more useful to point out a bug than a counter. Acked-by: Johannes Weiner