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Fri, 9 May 2025 15:18:01 +0000 (GMT) Message-ID: Date: Fri, 9 May 2025 17:18:00 +0200 Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCHv7 10/24] zram: add zlib compression backend support To: Sergey Senozhatsky Cc: Minchan Kim , linux-kernel@vger.kernel.org, Andrew Morton , Ilya Leoshkevich , Heiko Carstens , linux-s390@vger.kernel.org References: <20240902105656.1383858-1-senozhatsky@chromium.org> <20240902105656.1383858-11-senozhatsky@chromium.org> <6046d139-2a46-4824-bdfc-687750c1ee5b@linux.ibm.com> Content-Language: en-US From: Zaslonko Mikhail In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: YCRMyBXqOj2zZLWo7EFqIn6xcclGi_mQ X-Proofpoint-ORIG-GUID: YCRMyBXqOj2zZLWo7EFqIn6xcclGi_mQ X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNTA5MDE0OSBTYWx0ZWRfX3o+vXU8ldk5O RfrWfi3VdML5/kOaKq/Jl+RwwnF7FGvJR3JC4SBm6ckj3tXQfTckEiETcVMIoIaoloxKwfetr8l C2WT0EkHwhegTFcIBDbkE/JuuwhLExwr+24bONX+IRtKTnHvcP2LKTK680peMmQwRYQX+ki7Xzm sROU3X0s8q1vbRcyeWWpI9dB6KXUs59WAvjIitBP3O5uGP2bT9woGCAYjnygg2U2q884+zgGlqA O5+rSN2OtT5wbL5Uaz/5EdqlWMmkXp3WqC+RKjx1zh2l7hkdkpJMrA2aZdXyIF49CaYtEXnwPao qvUfZfuWzwPSTXCGSRpc0nCnbQpK8mQ3AcDNLP+ao0TwmUB5AlF8S7sRxmHTzRz9I537YKlLZMu axJABUYiKvLm5C0yRFF6lXzciBiMDhZf7pwK0uOfA+djLB8lTkku8XpjMkBMop3lb6K9asGB X-Authority-Analysis: v=2.4 cv=OcCYDgTY c=1 sm=1 tr=0 ts=681e1cad cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=IkcTkHD0fZMA:10 a=dt9VzEwgFbYA:10 a=UTuKZRxF6MC2NIc7D_4A:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.0.736,FMLib:17.12.80.40 definitions=2025-05-09_06,2025-05-08_04,2025-02-21_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 lowpriorityscore=0 phishscore=0 spamscore=0 bulkscore=0 impostorscore=0 malwarescore=0 clxscore=1015 mlxscore=0 priorityscore=1501 adultscore=0 mlxlogscore=999 classifier=spam authscore=0 authtc=n/a authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2504070000 definitions=main-2505090149 Hello, On 09.05.2025 03:38, Sergey Senozhatsky wrote: > Hello, > > On (25/05/08 16:19), Zaslonko Mikhail wrote: > [..] >>> +#include "backend_deflate.h" >>> + >>> +/* Use the same value as crypto API */ >>> +#define DEFLATE_DEF_WINBITS 11 >>> +#define DEFLATE_DEF_MEMLEVEL MAX_MEM_LEVEL >>> + > [..] >> The comment line says 'Use the same value as crypto API'... >> could you please clarify here? Are there some memory constraints? > > When zram transitioned from Crypto API (scomp) to custom compression > API I picked the CryptoAPI deflate DEFLATE_DEF_WINBITS value: > > crypto/deflate.c: DEFLATE_DEF_WINBITS 11 > > which is then passed to zlib_deflateInit2() and zlib_inflateInit2(). > >> I tried to build the kernel with DEFLATE_DEF_WINBITS set to 15 and >> verified that s390 hardware deflate acceleration works for zram devices >> with a deflate compression. > > If we define it as 15 on non-s390 machines, will there be any > consequences? Increased memory usage? By how much? On s390, setting windowBits to 15 would lead to zlib workarea size increased by 120K (0x24dc8 -> 0x42dc8) per compression stream, i.e. per online CPU. On non-s390 machine, that impact will be about 115K per stream. Increasing window size should improve deflate compression, although the compression speed might be affected. Couldn't find any relevant zlib benchmarks though. Not sure what other consequences might there be for zram. Do you see any? > Thanks, Mikhail