Mercurial > hg
view mercurial/pathencode.c @ 30212:260af19891f2
changegroup: increase write buffer size to 128k
By default, Python defers to the operating system for choosing the
default buffer size on opened files. On my Linux machine, the default
is 4k, which is really small for 2016.
This patch bumps the write buffer size when writing
changegroups/bundles to 128k. This matches the 128k read buffer
we already use on revlogs.
It's worth noting that this only impacts when writing to an explicit
file (such as during `hg bundle`). Buffers when writing to bundle
files via the repo vfs or to a temporary file are not impacted.
When producing a none-v2 bundle file of the mozilla-unified repository,
this change caused the number of write() system calls to drop from
952,449 to 29,788. After this change, the most frequent system
calls are fstat(), read(), lseek(), and open(). There were
2,523,672 system calls after this patch (so a net decrease of
~950k is statistically significant).
This change shows no performance change on my system. But I have a
high-end system with a fast SSD. It is quite possible this change
will have a significant impact on network file systems, where
extra network round trips due to excessive I/O system calls could
introduce significant latency.
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Sun, 16 Oct 2016 13:35:23 -0700 |
parents | f5607b6253da |
children |
line wrap: on
line source
/* pathencode.c - efficient path name encoding Copyright 2012 Facebook This software may be used and distributed according to the terms of the GNU General Public License, incorporated herein by reference. */ /* * An implementation of the name encoding scheme used by the fncache * store. The common case is of a path < 120 bytes long, which is * handled either in a single pass with no allocations or two passes * with a single allocation. For longer paths, multiple passes are * required. */ #define PY_SSIZE_T_CLEAN #include <Python.h> #include <assert.h> #include <ctype.h> #include <stdlib.h> #include <string.h> #include "util.h" /* state machine for the fast path */ enum path_state { START, /* first byte of a path component */ A, /* "AUX" */ AU, THIRD, /* third of a 3-byte sequence, e.g. "AUX", "NUL" */ C, /* "CON" or "COMn" */ CO, COMLPT, /* "COM" or "LPT" */ COMLPTn, L, LP, N, NU, P, /* "PRN" */ PR, LDOT, /* leading '.' */ DOT, /* '.' in a non-leading position */ H, /* ".h" */ HGDI, /* ".hg", ".d", or ".i" */ SPACE, DEFAULT /* byte of a path component after the first */ }; /* state machine for dir-encoding */ enum dir_state { DDOT, DH, DHGDI, DDEFAULT }; static inline int inset(const uint32_t bitset[], char c) { return bitset[((uint8_t)c) >> 5] & (1 << (((uint8_t)c) & 31)); } static inline void charcopy(char *dest, Py_ssize_t *destlen, size_t destsize, char c) { if (dest) { assert(*destlen < destsize); dest[*destlen] = c; } (*destlen)++; } static inline void memcopy(char *dest, Py_ssize_t *destlen, size_t destsize, const void *src, Py_ssize_t len) { if (dest) { assert(*destlen + len < destsize); memcpy((void *)&dest[*destlen], src, len); } *destlen += len; } static inline void hexencode(char *dest, Py_ssize_t *destlen, size_t destsize, uint8_t c) { static const char hexdigit[] = "0123456789abcdef"; charcopy(dest, destlen, destsize, hexdigit[c >> 4]); charcopy(dest, destlen, destsize, hexdigit[c & 15]); } /* 3-byte escape: tilde followed by two hex digits */ static inline void escape3(char *dest, Py_ssize_t *destlen, size_t destsize, char c) { charcopy(dest, destlen, destsize, '~'); hexencode(dest, destlen, destsize, c); } static Py_ssize_t _encodedir(char *dest, size_t destsize, const char *src, Py_ssize_t len) { enum dir_state state = DDEFAULT; Py_ssize_t i = 0, destlen = 0; while (i < len) { switch (state) { case DDOT: switch (src[i]) { case 'd': case 'i': state = DHGDI; charcopy(dest, &destlen, destsize, src[i++]); break; case 'h': state = DH; charcopy(dest, &destlen, destsize, src[i++]); break; default: state = DDEFAULT; break; } break; case DH: if (src[i] == 'g') { state = DHGDI; charcopy(dest, &destlen, destsize, src[i++]); } else state = DDEFAULT; break; case DHGDI: if (src[i] == '/') { memcopy(dest, &destlen, destsize, ".hg", 3); charcopy(dest, &destlen, destsize, src[i++]); } state = DDEFAULT; break; case DDEFAULT: if (src[i] == '.') state = DDOT; charcopy(dest, &destlen, destsize, src[i++]); break; } } return destlen; } PyObject *encodedir(PyObject *self, PyObject *args) { Py_ssize_t len, newlen; PyObject *pathobj, *newobj; char *path; if (!PyArg_ParseTuple(args, "O:encodedir", &pathobj)) return NULL; if (PyBytes_AsStringAndSize(pathobj, &path, &len) == -1) { PyErr_SetString(PyExc_TypeError, "expected a string"); return NULL; } newlen = len ? _encodedir(NULL, 0, path, len + 1) : 1; if (newlen == len + 1) { Py_INCREF(pathobj); return pathobj; } newobj = PyBytes_FromStringAndSize(NULL, newlen); if (newobj) { assert(PyBytes_Check(newobj)); Py_SIZE(newobj)--; _encodedir(PyBytes_AS_STRING(newobj), newlen, path, len + 1); } return newobj; } static Py_ssize_t _encode(const uint32_t twobytes[8], const uint32_t onebyte[8], char *dest, Py_ssize_t destlen, size_t destsize, const char *src, Py_ssize_t len, int encodedir) { enum path_state state = START; Py_ssize_t i = 0; /* * Python strings end with a zero byte, which we use as a * terminal token as they are not valid inside path names. */ while (i < len) { switch (state) { case START: switch (src[i]) { case '/': charcopy(dest, &destlen, destsize, src[i++]); break; case '.': state = LDOT; escape3(dest, &destlen, destsize, src[i++]); break; case ' ': state = DEFAULT; escape3(dest, &destlen, destsize, src[i++]); break; case 'a': state = A; charcopy(dest, &destlen, destsize, src[i++]); break; case 'c': state = C; charcopy(dest, &destlen, destsize, src[i++]); break; case 'l': state = L; charcopy(dest, &destlen, destsize, src[i++]); break; case 'n': state = N; charcopy(dest, &destlen, destsize, src[i++]); break; case 'p': state = P; charcopy(dest, &destlen, destsize, src[i++]); break; default: state = DEFAULT; break; } break; case A: if (src[i] == 'u') { state = AU; charcopy(dest, &destlen, destsize, src[i++]); } else state = DEFAULT; break; case AU: if (src[i] == 'x') { state = THIRD; i++; } else state = DEFAULT; break; case THIRD: state = DEFAULT; switch (src[i]) { case '.': case '/': case '\0': escape3(dest, &destlen, destsize, src[i - 1]); break; default: i--; break; } break; case C: if (src[i] == 'o') { state = CO; charcopy(dest, &destlen, destsize, src[i++]); } else state = DEFAULT; break; case CO: if (src[i] == 'm') { state = COMLPT; i++; } else if (src[i] == 'n') { state = THIRD; i++; } else state = DEFAULT; break; case COMLPT: switch (src[i]) { case '1': case '2': case '3': case '4': case '5': case '6': case '7': case '8': case '9': state = COMLPTn; i++; break; default: state = DEFAULT; charcopy(dest, &destlen, destsize, src[i - 1]); break; } break; case COMLPTn: state = DEFAULT; switch (src[i]) { case '.': case '/': case '\0': escape3(dest, &destlen, destsize, src[i - 2]); charcopy(dest, &destlen, destsize, src[i - 1]); break; default: memcopy(dest, &destlen, destsize, &src[i - 2], 2); break; } break; case L: if (src[i] == 'p') { state = LP; charcopy(dest, &destlen, destsize, src[i++]); } else state = DEFAULT; break; case LP: if (src[i] == 't') { state = COMLPT; i++; } else state = DEFAULT; break; case N: if (src[i] == 'u') { state = NU; charcopy(dest, &destlen, destsize, src[i++]); } else state = DEFAULT; break; case NU: if (src[i] == 'l') { state = THIRD; i++; } else state = DEFAULT; break; case P: if (src[i] == 'r') { state = PR; charcopy(dest, &destlen, destsize, src[i++]); } else state = DEFAULT; break; case PR: if (src[i] == 'n') { state = THIRD; i++; } else state = DEFAULT; break; case LDOT: switch (src[i]) { case 'd': case 'i': state = HGDI; charcopy(dest, &destlen, destsize, src[i++]); break; case 'h': state = H; charcopy(dest, &destlen, destsize, src[i++]); break; default: state = DEFAULT; break; } break; case DOT: switch (src[i]) { case '/': case '\0': state = START; memcopy(dest, &destlen, destsize, "~2e", 3); charcopy(dest, &destlen, destsize, src[i++]); break; case 'd': case 'i': state = HGDI; charcopy(dest, &destlen, destsize, '.'); charcopy(dest, &destlen, destsize, src[i++]); break; case 'h': state = H; memcopy(dest, &destlen, destsize, ".h", 2); i++; break; default: state = DEFAULT; charcopy(dest, &destlen, destsize, '.'); break; } break; case H: if (src[i] == 'g') { state = HGDI; charcopy(dest, &destlen, destsize, src[i++]); } else state = DEFAULT; break; case HGDI: if (src[i] == '/') { state = START; if (encodedir) memcopy(dest, &destlen, destsize, ".hg", 3); charcopy(dest, &destlen, destsize, src[i++]); } else state = DEFAULT; break; case SPACE: switch (src[i]) { case '/': case '\0': state = START; memcopy(dest, &destlen, destsize, "~20", 3); charcopy(dest, &destlen, destsize, src[i++]); break; default: state = DEFAULT; charcopy(dest, &destlen, destsize, ' '); break; } break; case DEFAULT: while (inset(onebyte, src[i])) { charcopy(dest, &destlen, destsize, src[i++]); if (i == len) goto done; } switch (src[i]) { case '.': state = DOT; i++; break; case ' ': state = SPACE; i++; break; case '/': state = START; charcopy(dest, &destlen, destsize, '/'); i++; break; default: if (inset(onebyte, src[i])) { do { charcopy(dest, &destlen, destsize, src[i++]); } while (i < len && inset(onebyte, src[i])); } else if (inset(twobytes, src[i])) { char c = src[i++]; charcopy(dest, &destlen, destsize, '_'); charcopy(dest, &destlen, destsize, c == '_' ? '_' : c + 32); } else escape3(dest, &destlen, destsize, src[i++]); break; } break; } } done: return destlen; } static Py_ssize_t basicencode(char *dest, size_t destsize, const char *src, Py_ssize_t len) { static const uint32_t twobytes[8] = { 0, 0, 0x87fffffe }; static const uint32_t onebyte[8] = { 1, 0x2bff3bfa, 0x68000001, 0x2fffffff, }; Py_ssize_t destlen = 0; return _encode(twobytes, onebyte, dest, destlen, destsize, src, len, 1); } static const Py_ssize_t maxstorepathlen = 120; static Py_ssize_t _lowerencode(char *dest, size_t destsize, const char *src, Py_ssize_t len) { static const uint32_t onebyte[8] = { 1, 0x2bfffbfb, 0xe8000001, 0x2fffffff }; static const uint32_t lower[8] = { 0, 0, 0x7fffffe }; Py_ssize_t i, destlen = 0; for (i = 0; i < len; i++) { if (inset(onebyte, src[i])) charcopy(dest, &destlen, destsize, src[i]); else if (inset(lower, src[i])) charcopy(dest, &destlen, destsize, src[i] + 32); else escape3(dest, &destlen, destsize, src[i]); } return destlen; } PyObject *lowerencode(PyObject *self, PyObject *args) { char *path; Py_ssize_t len, newlen; PyObject *ret; if (!PyArg_ParseTuple(args, "s#:lowerencode", &path, &len)) return NULL; newlen = _lowerencode(NULL, 0, path, len); ret = PyBytes_FromStringAndSize(NULL, newlen); if (ret) _lowerencode(PyBytes_AS_STRING(ret), newlen, path, len); return ret; } /* See store.py:_auxencode for a description. */ static Py_ssize_t auxencode(char *dest, size_t destsize, const char *src, Py_ssize_t len) { static const uint32_t twobytes[8]; static const uint32_t onebyte[8] = { ~0U, 0xffff3ffe, ~0U, ~0U, ~0U, ~0U, ~0U, ~0U, }; return _encode(twobytes, onebyte, dest, 0, destsize, src, len, 0); } static PyObject *hashmangle(const char *src, Py_ssize_t len, const char sha[20]) { static const Py_ssize_t dirprefixlen = 8; static const Py_ssize_t maxshortdirslen = 68; char *dest; PyObject *ret; Py_ssize_t i, d, p, lastslash = len - 1, lastdot = -1; Py_ssize_t destsize, destlen = 0, slop, used; while (lastslash >= 0 && src[lastslash] != '/') { if (src[lastslash] == '.' && lastdot == -1) lastdot = lastslash; lastslash--; } #if 0 /* All paths should end in a suffix of ".i" or ".d". Unfortunately, the file names in test-hybridencode.py violate this rule. */ if (lastdot != len - 3) { PyErr_SetString(PyExc_ValueError, "suffix missing or wrong length"); return NULL; } #endif /* If src contains a suffix, we will append it to the end of the new string, so make room. */ destsize = 120; if (lastdot >= 0) destsize += len - lastdot - 1; ret = PyBytes_FromStringAndSize(NULL, destsize); if (ret == NULL) return NULL; dest = PyBytes_AS_STRING(ret); memcopy(dest, &destlen, destsize, "dh/", 3); /* Copy up to dirprefixlen bytes of each path component, up to a limit of maxshortdirslen bytes. */ for (i = d = p = 0; i < lastslash; i++, p++) { if (src[i] == '/') { char d = dest[destlen - 1]; /* After truncation, a directory name may end in a space or dot, which are unportable. */ if (d == '.' || d == ' ') dest[destlen - 1] = '_'; /* The + 3 is to account for "dh/" in the beginning */ if (destlen > maxshortdirslen + 3) break; charcopy(dest, &destlen, destsize, src[i]); p = -1; } else if (p < dirprefixlen) charcopy(dest, &destlen, destsize, src[i]); } /* Rewind to just before the last slash copied. */ if (destlen > maxshortdirslen + 3) do { destlen--; } while (destlen > 0 && dest[destlen] != '/'); if (destlen > 3) { if (lastslash > 0) { char d = dest[destlen - 1]; /* The last directory component may be truncated, so make it safe. */ if (d == '.' || d == ' ') dest[destlen - 1] = '_'; } charcopy(dest, &destlen, destsize, '/'); } /* Add a prefix of the original file's name. Its length depends on the number of bytes left after accounting for hash and suffix. */ used = destlen + 40; if (lastdot >= 0) used += len - lastdot - 1; slop = maxstorepathlen - used; if (slop > 0) { Py_ssize_t basenamelen = lastslash >= 0 ? len - lastslash - 2 : len - 1; if (basenamelen > slop) basenamelen = slop; if (basenamelen > 0) memcopy(dest, &destlen, destsize, &src[lastslash + 1], basenamelen); } /* Add hash and suffix. */ for (i = 0; i < 20; i++) hexencode(dest, &destlen, destsize, sha[i]); if (lastdot >= 0) memcopy(dest, &destlen, destsize, &src[lastdot], len - lastdot - 1); assert(PyBytes_Check(ret)); Py_SIZE(ret) = destlen; return ret; } /* * Avoiding a trip through Python would improve performance by 50%, * but we don't encounter enough long names to be worth the code. */ static int sha1hash(char hash[20], const char *str, Py_ssize_t len) { static PyObject *shafunc; PyObject *shaobj, *hashobj; if (shafunc == NULL) { PyObject *hashlib, *name = PyBytes_FromString("hashlib"); if (name == NULL) return -1; hashlib = PyImport_Import(name); Py_DECREF(name); if (hashlib == NULL) { PyErr_SetString(PyExc_ImportError, "hashlib"); return -1; } shafunc = PyObject_GetAttrString(hashlib, "sha1"); Py_DECREF(hashlib); if (shafunc == NULL) { PyErr_SetString(PyExc_AttributeError, "module 'hashlib' has no " "attribute 'sha1'"); return -1; } } shaobj = PyObject_CallFunction(shafunc, "s#", str, len); if (shaobj == NULL) return -1; hashobj = PyObject_CallMethod(shaobj, "digest", ""); Py_DECREF(shaobj); if (hashobj == NULL) return -1; if (!PyBytes_Check(hashobj) || PyBytes_GET_SIZE(hashobj) != 20) { PyErr_SetString(PyExc_TypeError, "result of digest is not a 20-byte hash"); Py_DECREF(hashobj); return -1; } memcpy(hash, PyBytes_AS_STRING(hashobj), 20); Py_DECREF(hashobj); return 0; } #define MAXENCODE 4096 * 4 static PyObject *hashencode(const char *src, Py_ssize_t len) { char dired[MAXENCODE]; char lowered[MAXENCODE]; char auxed[MAXENCODE]; Py_ssize_t dirlen, lowerlen, auxlen, baselen; char sha[20]; baselen = (len - 5) * 3; if (baselen >= MAXENCODE) { PyErr_SetString(PyExc_ValueError, "string too long"); return NULL; } dirlen = _encodedir(dired, baselen, src, len); if (sha1hash(sha, dired, dirlen - 1) == -1) return NULL; lowerlen = _lowerencode(lowered, baselen, dired + 5, dirlen - 5); auxlen = auxencode(auxed, baselen, lowered, lowerlen); return hashmangle(auxed, auxlen, sha); } PyObject *pathencode(PyObject *self, PyObject *args) { Py_ssize_t len, newlen; PyObject *pathobj, *newobj; char *path; if (!PyArg_ParseTuple(args, "O:pathencode", &pathobj)) return NULL; if (PyBytes_AsStringAndSize(pathobj, &path, &len) == -1) { PyErr_SetString(PyExc_TypeError, "expected a string"); return NULL; } if (len > maxstorepathlen) newlen = maxstorepathlen + 2; else newlen = len ? basicencode(NULL, 0, path, len + 1) : 1; if (newlen <= maxstorepathlen + 1) { if (newlen == len + 1) { Py_INCREF(pathobj); return pathobj; } newobj = PyBytes_FromStringAndSize(NULL, newlen); if (newobj) { assert(PyBytes_Check(newobj)); Py_SIZE(newobj)--; basicencode(PyBytes_AS_STRING(newobj), newlen, path, len + 1); } } else newobj = hashencode(path, len + 1); return newobj; }