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Tue, 27 Feb 2024 19:26:38 -0800 (PST) Received: from google.com ([2401:fa00:8f:203:f4f0:fb4d:aa01:9068]) by smtp.gmail.com with ESMTPSA id 5-20020a170902c24500b001d7252fef6bsm2217289plg.299.2024.02.27.19.26.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 27 Feb 2024 19:26:38 -0800 (PST) Date: Wed, 28 Feb 2024 12:26:33 +0900 From: Sergey Senozhatsky To: Chengming Zhou Cc: minchan@kernel.org, senozhatsky@chromium.org, akpm@linux-foundation.org, hannes@cmpxchg.org, nphamcs@gmail.com, yosryahmed@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] mm/zsmalloc: don't need to reserve LSB in handle Message-ID: <20240228032633.GD11972@google.com> References: <20240228023854.3511239-1-chengming.zhou@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240228023854.3511239-1-chengming.zhou@linux.dev> X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: B0CDA20014 X-Stat-Signature: qd5gznsqi3mrso8erinffaj6agdohmpu X-Rspam-User: X-HE-Tag: 1709090799-449991 X-HE-Meta: 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 LB0B1GwR moYufywiMbYXJjp/HWC5Tv9zACNDN3kbiRV9X X-Bogosity: Ham, tests=bogofilter, spamicity=0.018485, 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 (24/02/28 02:38), Chengming Zhou wrote: > We will save allocated tag in the object header to indicate that it's > allocated. > > handle |= OBJ_ALLOCATED_TAG; > > So the object header needs to reserve LSB for this tag bit. > > But the handle itself doesn't need to reserve LSB to save tag, since > it's only used to find the position of object, by (pfn + obj_idx). > So remove LSB reserve from handle, one more bit can be used as obj_idx. > > Signed-off-by: Chengming Zhou Reviewed-by: Sergey Senozhatsky