Mercurial > hg
view mercurial/bitmanipulation.h @ 47120:7109a38830c9
dirstate-tree: Fold "tracked descendants" counter update in main walk
For the purpose of implementing `has_tracked_dir` (which means "has tracked
descendants) without an expensive sub-tree traversal, we maintaing a counter
of tracked descendants on each "directory" node of the tree-shaped dirstate.
Before this changeset, mutating or inserting a node at a given path would
involve:
* Walking the tree from root through ancestors to find the node or the spot
where to insert it
* Looking at the previous node if any to decide what counter update is needed
* Performing any node mutation
* Walking the tree *again* to update counters in ancestor nodes
When profiling `hg status` on a large repo, this second walk takes times
while loading a the dirstate from disk.
It turns out we have enough information to decide before he first tree walk
what counter update is needed. This changeset merges the two walks, gaining
~10% of the total time for `hg update` (in the same hyperfine benchmark as
the previous changeset).
---
Profiling was done by compiling with this `.cargo/config`:
[profile.release]
debug = true
then running with:
py-spy record -r 500 -n -o /tmp/hg.json --format speedscope -- \
./hg status -R $REPO --config experimental.dirstate-tree.in-memory=1
then visualizing the recorded JSON file in https://www.speedscope.app/
Differential Revision: https://phab.mercurial-scm.org/D10554
author | Simon Sapin <simon.sapin@octobus.net> |
---|---|
date | Fri, 30 Apr 2021 14:22:14 +0200 |
parents | eed42f1c22d6 |
children | d86908050375 |
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#ifndef _HG_BITMANIPULATION_H_ #define _HG_BITMANIPULATION_H_ #include <string.h> #include "compat.h" /* Reads a 64 bit integer from big-endian bytes. Assumes that the data is long enough */ static inline uint64_t getbe64(const char *c) { const unsigned char *d = (const unsigned char *)c; return ((((uint64_t)d[0]) << 56) | (((uint64_t)d[1]) << 48) | (((uint64_t)d[2]) << 40) | (((uint64_t)d[3]) << 32) | (((uint64_t)d[4]) << 24) | (((uint64_t)d[5]) << 16) | (((uint64_t)d[6]) << 8) | (d[7])); } static inline uint32_t getbe32(const char *c) { const unsigned char *d = (const unsigned char *)c; return ((((uint32_t)d[0]) << 24) | (((uint32_t)d[1]) << 16) | (((uint32_t)d[2]) << 8) | (d[3])); } static inline int16_t getbeint16(const char *c) { const unsigned char *d = (const unsigned char *)c; return ((d[0] << 8) | (d[1])); } static inline uint16_t getbeuint16(const char *c) { const unsigned char *d = (const unsigned char *)c; return ((d[0] << 8) | (d[1])); } /* Writes a 64 bit integer to bytes in a big-endian format. Assumes that the buffer is long enough */ static inline void putbe64(uint64_t x, char *c) { c[0] = (x >> 56) & 0xff; c[1] = (x >> 48) & 0xff; c[2] = (x >> 40) & 0xff; c[3] = (x >> 32) & 0xff; c[4] = (x >> 24) & 0xff; c[5] = (x >> 16) & 0xff; c[6] = (x >> 8) & 0xff; c[7] = (x)&0xff; } static inline void putbe32(uint32_t x, char *c) { c[0] = (x >> 24) & 0xff; c[1] = (x >> 16) & 0xff; c[2] = (x >> 8) & 0xff; c[3] = (x)&0xff; } static inline double getbefloat64(const char *c) { const unsigned char *d = (const unsigned char *)c; double ret; int i; uint64_t t = 0; for (i = 0; i < 8; i++) { t = (t << 8) + d[i]; } memcpy(&ret, &t, sizeof(t)); return ret; } #endif