Mercurial > hg
view mercurial/pathencode.c @ 26379:39d643252b9f
revlog: use existing file handle when reading during _addrevision
_addrevision() may need to read from revlogs as part of computing
deltas. Previously, we would flush existing file handles and open
a new, short-lived file handle to perform the reading.
If we have an existing file handle, it seems logical to reuse it
for reading instead of opening a new file handle. This patch
makes that the new behavior.
After this patch, revlog files are only reopened when adding
revisions if the revlog is switched from inline to non-inline.
On Linux when unbundling a bundle of the mozilla-central repo, this
patch has the following impact on system call counts:
Call Before After Delta
write 827,639 673,390 -154,249
open 700,103 684,089 -16,014
read 74,489 74,489 0
fstat 493,924 461,896 -32,028
close 249,131 233,117 -16,014
stat 242,001 242,001 0
lstat 18,676 18,676 0
lseek 20,268 20,268 0
ioctl 14,652 13,173 -1,479
TOTAL 3,180,758 2,930,679 -250,079
It's worth noting that many of the open() calls fail due to missing
files. That's why there are many more open() calls than close().
Despite the significant system call reduction, this change does not
seem to have a significant performance impact on Linux.
On Windows 10 (not a VM, on a SSD), this patch appears to reduce
unbundle time for mozilla-central from ~960s to ~920s. This isn't
as significant as I was hoping. But a decrease it is nonetheless.
Still, Windows unbundle performance is still >2x slower than Linux.
Despite the lack of significant gains, fewer system calls is fewer
system calls. If nothing else, this will narrow the focus of potential
areas to optimize in the future.
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Sun, 27 Sep 2015 16:08:18 -0700 |
parents | 822f46b80fa9 |
children | 673ba59669b5 |
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 (PyString_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 = PyString_FromStringAndSize(NULL, newlen); if (newobj) { PyString_GET_SIZE(newobj)--; _encodedir(PyString_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 = PyString_FromStringAndSize(NULL, newlen); if (ret) newlen = _lowerencode(PyString_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 = PyString_FromStringAndSize(NULL, destsize); if (ret == NULL) return NULL; dest = PyString_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); PyString_GET_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 *util, *name = PyString_FromString("mercurial.util"); if (name == NULL) return -1; util = PyImport_Import(name); Py_DECREF(name); if (util == NULL) { PyErr_SetString(PyExc_ImportError, "mercurial.util"); return -1; } shafunc = PyObject_GetAttrString(util, "sha1"); Py_DECREF(util); if (shafunc == NULL) { PyErr_SetString(PyExc_AttributeError, "module 'mercurial.util' 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 (!PyString_Check(hashobj) || PyString_GET_SIZE(hashobj) != 20) { PyErr_SetString(PyExc_TypeError, "result of digest is not a 20-byte hash"); Py_DECREF(hashobj); return -1; } memcpy(hash, PyString_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 (PyString_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 = PyString_FromStringAndSize(NULL, newlen); if (newobj) { PyString_GET_SIZE(newobj)--; basicencode(PyString_AS_STRING(newobj), newlen, path, len + 1); } } else newobj = hashencode(path, len + 1); return newobj; }