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Sat, 22 Feb 2025 00:21:12 -0800 (PST) MIME-Version: 1.0 References: In-Reply-To: From: Barry Song <21cnbao@gmail.com> Date: Sat, 22 Feb 2025 21:21:00 +1300 X-Gm-Features: AWEUYZnvD7tVU43TzzmfD0LP6gJCzSJnHAZvx6v8dXhBzUxBUHngxlVnDbI9AGg Message-ID: Subject: Re: [PATCH v5 02/12] crypto: acomp - Define new interfaces for compress/decompress batching. To: Herbert Xu Cc: Yosry Ahmed , Minchan Kim , Sergey Senozhatsky , "Sridhar, Kanchana P" , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "hannes@cmpxchg.org" , "nphamcs@gmail.com" , "chengming.zhou@linux.dev" , "usamaarif642@gmail.com" , "ryan.roberts@arm.com" , "akpm@linux-foundation.org" , "linux-crypto@vger.kernel.org" , "davem@davemloft.net" , "clabbe@baylibre.com" , "ardb@kernel.org" , "ebiggers@google.com" , "surenb@google.com" , "Accardi, Kristen C" , "Feghali, Wajdi K" , "Gopal, Vinodh" Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 1B7DE100008 X-Stat-Signature: nkyg4smp35qkkccqzqmi8hk54w8qpssm X-Rspam-User: X-HE-Tag: 1740212472-769682 X-HE-Meta: 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 wL5eyFrz KJaneEJbUDyzZ+avM4vG+wrISRv6CPVLNTOAmaW4J7o7pbwF1dxncSYAESSauxivgOGyv+aifaKES3LT9KLuryXAE0lnNKA/xlfvvIhL58DTOfjERAzEUIlc78egzlAjUnMnRzC9WmJUS1aqtcL0ZLdcsnkqCCBwvZw3kia32FjBvaHBEJD3KckFBfB8+jZGW92aGCJpDHhw6ZdkJY8+X+7H+vzhiRfDWdukaoox7Pun9wbih1jGLv2sbuxk7wN2ux5MyN6tqVBUfzSxxz6OyYyzydYU58rSn+Ld/VUnmxsh8WIs4Bpz0jvRBdzztaV1zrgTsn87LqzTPfrE3OmEOHauaAK/HFPHsEcvmobaK8DpOsogq6wGLVVhnBjqPLLqyin899PimGKs1mwzE8ZrrunlwpfclbUWRP4XImgBTGqaC+k8= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000005, 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 Sat, Feb 22, 2025 at 8:23=E2=80=AFPM Herbert Xu wrote: > > On Sat, Feb 22, 2025 at 08:13:13PM +1300, Barry Song wrote: > > > > Somehow, I find your comment reasonable. Another point I want > > to mention is the semantic difference. For example, in a system > > with only one algorithm, a dst_buf overflow still means a successful > > swap-out. However, other errors actually indicate an I/O failure. > > In such cases, vmscan.c will log the relevant error in pageout() to > > notify the user. > > I'm talking specifically about the error from the Crypto API, > not any other error. So if you werer using some sort of an > offload device to do the compression, that could indeed fail > due to an IO error (perhaps the PCI bus is on fire :) > > But because that's reported through the Crypto API, it should > not be treated any differently than an incompressible page, > except for reporting purposes. I'm referring more to the mm subsystem :-) Let me provide a concrete example. Below is a small program that will swap out 16MB of memory to zRAM: #include #include #include #include #include #define MB (1024 * 1024) #define SIZE (16 * MB) int main() { void *addr =3D mmap(NULL, SIZE, PROT_READ | PROT_WRITE, MAP_ANON | MAP_PRIVATE, -1, 0); if (addr =3D=3D MAP_FAILED) { perror("mmap failed"); return 1; } for (size_t i =3D 0; i < SIZE / sizeof(int); i++) { ((int*)addr)[i] =3D rand(); } if (madvise(addr, SIZE, MADV_PAGEOUT) !=3D 0) { perror("madvise failed"); return 1; } while (1); return 0; } For errors other than dst_buf overflow, we receive: / # ./a.out & / # free total used free shared buff/cache avai= lable Mem: 341228 77036 251872 0 20600 2= 64192 Swap: 2703356 0 2703356 [1]+ Done ./a.out / # cat /proc/vmstat | grep swp pswpin 0 pswpout 0 ... No memory has been swapped out, the swap-out counter is zero, and the swap file is not used at all. If this is an incompressible page(I mean dst_buf overflow error), there is no actual issue, and we get the following: / # / # free total used free shared buff/cache avai= lable Mem: 341228 92948 236248 0 20372 2= 48280 Swap: 2703356 16384 2686972 / # cat /proc/vmstat | grep swp pswpin 0 pswpout 4096 ... > > Cheers, > -- > Email: Herbert Xu > Home Page: http://gondor.apana.org.au/~herbert/ > PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt > Thanks Barry