Date: Tue, 31 Mar 2015 17:58:52 +0000 From: bugzilla-noreply@freebsd.org To: freebsd-bugs@FreeBSD.org Subject: [Bug 199072] libmd inefficient read() calls Message-ID: <bug-199072-8@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=199072 Bug ID: 199072 Summary: libmd inefficient read() calls Product: Base System Version: 11.0-CURRENT Hardware: Any OS: Any Status: New Severity: Affects Only Me Priority: --- Component: bin Assignee: freebsd-bugs@FreeBSD.org Reporter: kcwu@csie.org src/lib/libmd/mdXhl.c MDXFileChunk(const char *filename, char *buf, off_t ofs, off_t len) { unsigned char buffer[BUFSIZ]; where BUFSIZE is 1024 from stdio.h This will make lots of read(2) syscalls. All utilities depend on libmd, including md5(1) and sha256(1), are affected. ============== For example, on my system, (file content is already cached in ram) $ du -h file.bin 4.9G file.bin $ time md5 file.bin MD5 (file.bin) = 422bb7e6759dee9dd1af940f9d9db5ab real 0m31.848s user 0m11.500s sys 0m19.526s Notice that 19.526s spend in sys. You could also verify the read size is 1024 using truss(1) $ truss md5 file.bin ... read(3,"^3fEiRA\M^S\^]\M-Rf\M-7\M-E\M-g"...,1024) = 1024 (0x400) ... ============== If modified buffer[] to larger, say 1MB, md5(1) becomes much faster. $ time md5 file.bin MD5 (file.bin) = 422bb7e6759dee9dd1af940f9d9db5ab real 0m14.369s user 0m11.220s sys 0m1.933s -- You are receiving this mail because: You are the assignee for the bug.
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