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Tue, 10 Mar 2026 22:22:06 -0700 (PDT) Received: from google.com ([2a00:79e0:2031:6:93a4:8281:fe98:426a]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-829f6dc0c9bsm978368b3a.5.2026.03.10.22.22.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 10 Mar 2026 22:22:05 -0700 (PDT) Date: Wed, 11 Mar 2026 14:22:02 +0900 From: Sergey Senozhatsky To: gao xu Cc: Sergey Senozhatsky , Minchan Kim , Jens Axboe , "linux-block@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Andrew Morton , "surenb@google.com" , zhouxiaolong Subject: Re: zram: Optimize LZ4 dictionary compression performance Message-ID: References: Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On (26/03/11 04:00), gao xu wrote: > > On (26/03/10 02:54), gao xu wrote: > > > + memcpy(zctx->cstrm, &drv->base_cstream, > > > + sizeof(*zctx->cstrm)); > > > > Do we need to do this memcpy() every time? > memcpy is a replacement for LZ4_loadDict. LZ4_loadDict updates > the LZ4 hash table using the dictionary. Furthermore, LZ4 also > updates its hash table with the results of the previous compression. > Therefore, to ensure the compression dictionary remains effective, we > would need to reset the hash table every time, which would involve > executing memcpy() or LZ4_loadDict() OK, I see. (I assume you tested and verified that.)