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Fri, 23 Oct 2026 22:48:38 -0700 (PDT) Received: from google.com ([2a00:79e0:2031:6:f7b9:fe46:772a:da49]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-369e8d93663sm4221618eec.13.2026.10.23.22.48.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 23 Oct 2026 22:48:37 -0700 (PDT) Date: Sat, 24 Oct 2026 14:48:32 +0900 From: Sergey Senozhatsky To: Hillf Danton Cc: Sergey Senozhatsky , Barry Song <21cnbao@gmail.com>, Andrew Morton , Brian Geffon , linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v6 09/13] zram: split zcomp into separate R/W streams Message-ID: References: <20261023114050.1011-1-hdanton@sina.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261023114050.1011-1-hdanton@sina.com> On (26/10/23 19:40), Hillf Danton wrote: [..] > > writers vs readers 3 runs > > > > BASE+PE IOPS 1,271k avg 5.57us sd 1,393us p99.99 27.5us max 1,581,800us > > IOPS 1,461k avg 3.43us sd 78us p99.99 23.9us max 227,015us > > IOPS 1,444k avg 3.48us sd 222us p99.99 23.9us max 592,628us > > PATCHED+PE IOPS 1,457k avg 3.32us sd 18us p99.99 27.5us max 5,620us > > IOPS 1,464k avg 3.31us sd 17us p99.99 24.2us max 5,621us > > IOPS 1,475k avg 3.29us sd 16us p99.99 26.5us max 5,620us BASE+PE looked noisy, so I sat down and tested properly (also tested zstd and various compression levels). (PE enabled for all tests) ######## zstd compression level 3 W-vs-R BASE IOPS 1,154k avg 7.84us sd 444us max 697,634us IOPS 881k avg 14.16us sd 2,242us max 1,387,000us IOPS 704k avg 20.43us sd 3,499us max 2,058,300us IOPS 563k avg 29.02us sd 3,910us max 1,649,800us IOPS 626k avg 24.79us sd 4,013us max 2,085,800us IOPS 976k avg 11.54us sd 1,518us max 1,165,800us IOPS 1,178k avg 7.44us sd 22us max 3,103us IOPS 1,120k avg 7.39us sd 21us max 7,222us IOPS 522k avg 32.51us sd 4,311us max 1,598,300us IOPS 581k avg 27.54us sd 3,626us max 1,448,600us IOPS 1,160k avg 7.69us sd 352us max 702,099us IOPS 1,169k avg 7.52us sd 129us max 281,428us IOPS 954k avg 12.06us sd 1,705us max 1,545,600us IOPS 1,029k avg 10.24us sd 1,156us max 976,065us IOPS 1,169k avg 7.48us sd 24us max 4,305us IOPS 1,177k avg 7.45us sd 53us max 118,777us IOPS 579k avg 27.43us sd 3,661us max 1,615,800us IOPS 1,169k avg 7.52us sd 115us max 228,074us IOPS 1,110k avg 8.59us sd 985us max 1,288,000us IOPS 1,177k avg 7.45us sd 29us max 72,245us IOPS 580k avg 27.74us sd 3,755us max 1,507,000us PATCHED IOPS 1,179k avg 7.40us sd 23us max 7,404us IOPS 1,179k avg 7.41us sd 22us max 2,857us IOPS 1,176k avg 7.40us sd 22us max 6,615us IOPS 1,175k avg 7.44us sd 23us max 5,623us IOPS 1,176k avg 7.42us sd 24us max 5,625us IOPS 1,173k avg 7.42us sd 24us max 5,632us IOPS 1,172k avg 7.41us sd 23us max 6,223us IOPS 1,173k avg 7.40us sd 25us max 5,848us IOPS 1,173k avg 7.40us sd 24us max 7,563us IOPS 1,172k avg 7.42us sd 24us max 5,625us IOPS 1,175k avg 7.42us sd 23us max 5,626us IOPS 1,177k avg 7.42us sd 23us max 4,243us IOPS 1,170k avg 7.46us sd 25us max 5,622us IOPS 1,178k avg 7.40us sd 22us max 3,213us IOPS 1,167k avg 7.43us sd 25us max 7,593us IOPS 1,174k avg 7.44us sd 23us max 6,971us IOPS 1,179k avg 7.38us sd 23us max 3,477us IOPS 1,180k avg 7.39us sd 23us max 2,894us IOPS 1,145k avg 7.37us sd 21us max 4,048us IOPS 1,177k avg 7.38us sd 22us max 5,620us IOPS 1,177k avg 7.40us sd 23us max 5,623us IOPS: BASE 932k (+-260k), PATCHED 1,174k (+-7k), 21 runs each. significant difference at 95% confidence: PATCHED is 241k (25.9%) higher; 95% CI [+136k, +353k], Welch's t-test p = 0.000 max latency: BASE 3.1..2,085.8 ms, PATCHED 2.9..7.6 ms runs with max over 100 ms: BASE 17 of 21, PATCHED 0 of 21; over 1 s: BASE 11 of 21, PATCHED 0 of 21 ######## zstd compression level 12 W-vs-R BASE IOPS 690k avg 21.53us sd 3,088us max 1,635,500us IOPS 478k avg 36.51us sd 4,385us max 1,941,300us IOPS 822k avg 16.13us sd 2,865us max 2,263,800us IOPS 1,161k avg 7.73us sd 114us max 190,307us IOPS 780k avg 17.56us sd 2,717us max 1,550,500us IOPS 1,166k avg 7.66us sd 40us max 94,522us IOPS 585k avg 27.51us sd 3,847us max 1,550,600us IOPS 1,147k avg 7.97us sd 344us max 496,483us IOPS 1,166k avg 7.64us sd 49us max 115,243us IOPS 1,163k avg 7.66us sd 23us max 7,006us IOPS 1,071k avg 9.42us sd 1,489us max 1,915,500us IOPS 962k avg 11.88us sd 2,168us max 1,904,500us IOPS 607k avg 26.05us sd 3,538us max 1,591,100us IOPS 1,167k avg 7.63us sd 23us max 2,903us IOPS 1,157k avg 7.78us sd 198us max 418,930us IOPS 1,163k avg 7.66us sd 40us max 100,346us IOPS 1,162k avg 7.70us sd 32us max 82,602us IOPS 488k avg 35.43us sd 4,340us max 1,786,400us IOPS 563k avg 28.85us sd 3,989us max 2,209,500us IOPS 843k avg 15.43us sd 2,490us max 1,572,100us IOPS 604k avg 26.30us sd 3,560us max 1,555,700us PATCHED IOPS 1,166k avg 7.60us sd 23us max 5,623us IOPS 1,169k avg 7.58us sd 23us max 5,629us IOPS 1,157k avg 7.67us sd 27us max 5,639us IOPS 1,166k avg 7.61us sd 24us max 5,644us IOPS 1,160k avg 7.64us sd 26us max 7,543us IOPS 1,167k avg 7.60us sd 24us max 7,514us IOPS 1,160k avg 7.61us sd 25us max 6,643us IOPS 1,162k avg 7.65us sd 25us max 7,315us IOPS 1,161k avg 7.66us sd 24us max 6,237us IOPS 1,158k avg 7.62us sd 27us max 7,688us IOPS 1,167k avg 7.58us sd 24us max 5,637us IOPS 1,165k avg 7.59us sd 24us max 7,098us IOPS 948k avg 7.58us sd 23us max 7,808us IOPS 1,166k avg 7.60us sd 24us max 5,621us IOPS 1,166k avg 7.58us sd 24us max 5,672us IOPS 1,162k avg 7.65us sd 25us max 6,824us IOPS 1,165k avg 7.59us sd 24us max 7,078us IOPS 1,168k avg 7.58us sd 23us max 6,191us IOPS 1,170k avg 7.56us sd 22us max 2,851us IOPS 1,171k avg 7.55us sd 22us max 2,834us IOPS 1,166k avg 7.59us sd 24us max 5,627us IOPS: BASE 902k (+-269k), PATCHED 1,154k (+-47k), 21 runs each. significant difference at 95% confidence: PATCHED is 252k (27.9%) higher; 95% CI [+142k, +367k], Welch's t-test p = 0.000 max latency: BASE 2.9..2,263.8 ms, PATCHED 2.8..7.8 ms runs with max over 100 ms: BASE 17 of 21, PATCHED 0 of 21; over 1 s: BASE 12 of 21, PATCHED 0 of 21 ######## lz4 W-vs-R BASE IOPS 1,422k avg 3.84us sd 418us max 619,495us IOPS 1,450k avg 3.57us sd 326us max 609,723us IOPS 1,414k avg 3.92us sd 543us max 879,815us IOPS 1,451k avg 3.56us sd 253us max 503,428us IOPS 1,460k avg 3.40us sd 68us max 135,825us IOPS 1,413k avg 3.31us sd 44us max 188,450us IOPS 1,432k avg 3.73us sd 503us max 844,228us IOPS 1,387k avg 4.20us sd 719us max 961,827us IOPS 1,464k avg 3.38us sd 44us max 133,675us IOPS 1,469k avg 3.38us sd 22us max 65,812us IOPS 1,465k avg 3.40us sd 49us max 111,788us IOPS 1,465k avg 3.39us sd 64us max 174,040us IOPS 1,467k avg 3.38us sd 36us max 97,821us IOPS 1,445k avg 3.63us sd 343us max 671,026us IOPS 1,472k avg 3.35us sd 27us max 86,795us IOPS 1,473k avg 3.33us sd 44us max 138,096us IOPS 1,439k avg 3.71us sd 353us max 619,815us IOPS 1,398k avg 3.36us sd 54us max 206,815us IOPS 1,471k avg 3.36us sd 15us max 2,832us IOPS 1,407k avg 4.02us sd 629us max 1,074,800us IOPS 1,465k avg 3.40us sd 63us max 158,779us PATCHED IOPS 1,471k avg 3.30us sd 15us max 6,946us IOPS 1,473k avg 3.29us sd 16us max 5,618us IOPS 1,474k avg 3.29us sd 15us max 5,615us IOPS 1,473k avg 3.29us sd 15us max 5,625us IOPS 1,440k avg 3.26us sd 13us max 2,829us IOPS 1,456k avg 3.30us sd 15us max 5,623us IOPS 1,476k avg 3.29us sd 15us max 2,835us IOPS 1,464k avg 3.28us sd 16us max 6,063us IOPS 1,468k avg 3.32us sd 19us max 6,692us IOPS 1,465k avg 3.30us sd 17us max 6,834us IOPS 1,468k avg 3.28us sd 16us max 7,268us IOPS 1,463k avg 3.31us sd 17us max 6,480us IOPS 1,454k avg 3.33us sd 20us max 8,418us IOPS 1,452k avg 3.32us sd 19us max 5,621us IOPS 1,477k avg 3.27us sd 14us max 2,834us IOPS 1,468k avg 3.30us sd 16us max 5,617us IOPS 1,475k avg 3.30us sd 16us max 3,884us IOPS 1,475k avg 3.30us sd 16us max 5,692us IOPS 1,471k avg 3.30us sd 15us max 5,616us IOPS 1,473k avg 3.28us sd 16us max 7,014us IOPS 1,475k avg 3.28us sd 15us max 5,616us IOPS: BASE 1,444k (+-27k), PATCHED 1,467k (+-10k), 21 runs each. significant difference at 95% confidence: PATCHED is 23k (1.6%) higher; 95% CI [+11k, +35k], Welch's t-test p = 0.001 max latency: BASE 2.8..1,074.8 ms, PATCHED 2.8..8.4 ms runs with max over 100 ms: BASE 17 of 21, PATCHED 0 of 21; over 1 s: BASE 1 of 21, PATCHED 0 of 21