upstream/mercurial-mirror Files · mercurial/cext/util.h

discovery: slowly increase sampling size...

discovery: slowly increase sampling size Some pathological discovery runs can requires many roundtrip. When this happens things can get very slow. To make the algorithm more resilience again such pathological case. We slowly increase the sample size with each roundtrip (+5%). This will have a negligible impact on "normal" discovery with few roundtrips, but a large positive impact of case with many roundtrips. Asking more question per roundtrip helps to reduce the undecided set faster. Instead of reducing the undecided set a linear speed (in the worst case), we reduce it as a guaranteed (small) exponential rate. The data below show this slow ramp up in sample size: round trip | 1 | 5 | 10 | 20 | 50 | 100 | 130 | sample size | 200 | 254 | 321 | 517 | 2 199 | 25 123 | 108 549 | covered nodes | 200 | 1 357 | 2 821 | 7 031 | 42 658 | 524 530 | 2 276 755 | To be a bit more concrete, lets take a very pathological case as an example. We are doing discovery from a copy of Mozilla-try to a more recent version of mozilla-unified. Mozilla-unified heads are unknown to the mozilla-try repo and there are over 1 million "missing" changesets. (the discovery is "local" to avoid network interference) Without this change, the discovery: - last 1858 seconds (31 minutes), - does 1700 round trip, - asking about 340 000 nodes. With this change, the discovery: - last 218 seconds (3 minutes, 38 seconds a -88% improvement), - does 94 round trip (-94%), - asking about 344 211 nodes (+1%). Of course, this is an extreme case (and 3 minutes is still slow). However this give a good example of how this sample size increase act as a safety net catching any bad situations. We could image a steeper increase than 5%. For example 10% would give the following number: round trip | 1 | 5 | 10 | 20 | 50 | 75 | 100 | sample size | 200 | 321 | 514 | 1 326 | 23 060 | 249 812 | 2 706 594 | covered nodes | 200 | 1 541 | 3 690 | 12 671 | 251 871 | 2 746 254 | 29 770 966 | In parallel, it is useful to understand these pathological cases and improve them. However the current change provides a general purpose safety net to smooth the impact of pathological cases. To avoid issue with older http server, the increase in sample size only occurs if the protocol has not limit on command argument size.

Augie Fackler - - Load All Authors

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      /*

       util.h - utility functions for interfacing with the various python APIs.

       This software may be used and distributed according to the terms of

       the GNU General Public License, incorporated herein by reference.

      */

      #ifndef _HG_UTIL_H_

      #define _HG_UTIL_H_

      #include "compat.h"

      #if PY_MAJOR_VERSION >= 3

      #define IS_PY3K

      #endif

      /* helper to switch things like string literal depending on Python version */

      #ifdef IS_PY3K

      #define PY23(py2, py3) py3

      #else

      #define PY23(py2, py3) py2

      #endif

      /* clang-format off */

      typedef struct {

      	PyObject_HEAD

      	char state;

      	int mode;

      	int size;

      	int mtime;

      } dirstateTupleObject;

      /* clang-format on */

      extern PyTypeObject dirstateTupleType;

      #define dirstate_tuple_check(op) (Py_TYPE(op) == &dirstateTupleType)

      #ifndef MIN

      #define MIN(a, b) (((a) < (b)) ? (a) : (b))

      #endif

      /* VC9 doesn't include bool and lacks stdbool.h based on my searching */

      #if defined(_MSC_VER) || __STDC_VERSION__ < 199901L

      #define true 1

      #define false 0

      typedef unsigned char bool;

      #else

      #include <stdbool.h>

      #endif

      static inline PyObject *_dict_new_presized(Py_ssize_t expected_size)

      {

      	/* _PyDict_NewPresized expects a minused parameter, but it actually

      	   creates a dictionary that's the nearest power of two bigger than the

      	   parameter. For example, with the initial minused = 1000, the

      	   dictionary created has size 1024. Of course in a lot of cases that

      	   can be greater than the maximum load factor Python's dict object

      	   expects (= 2/3), so as soon as we cross the threshold we'll resize

      	   anyway. So create a dictionary that's at least 3/2 the size. */

      	return _PyDict_NewPresized(((1 + expected_size) / 2) * 3);

      }

      /* Convert a PyInt or PyLong to a long. Returns false if there is an

         error, in which case an exception will already have been set. */

      static inline bool pylong_to_long(PyObject *pylong, long *out)

      {

      	*out = PyLong_AsLong(pylong);

      	/* Fast path to avoid hitting PyErr_Occurred if the value was obviously

      	 * not an error. */

      	if (*out != -1) {

      		return true;

      	}

      	return PyErr_Occurred() == NULL;

      }

      #endif /* _HG_UTIL_H_ */

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				/*
				util.h - utility functions for interfacing with the various python APIs.

				This software may be used and distributed according to the terms of
				the GNU General Public License, incorporated herein by reference.
				*/

				#ifndef _HG_UTIL_H_
				#define _HG_UTIL_H_

				#include "compat.h"

				#if PY_MAJOR_VERSION >= 3
				#define IS_PY3K
				#endif

				/* helper to switch things like string literal depending on Python version */
				#ifdef IS_PY3K
				#define PY23(py2, py3) py3
				#else
				#define PY23(py2, py3) py2
				#endif

				/* clang-format off */
				typedef struct {
				PyObject_HEAD
				char state;
				int mode;
				int size;
				int mtime;
				} dirstateTupleObject;
				/* clang-format on */

				extern PyTypeObject dirstateTupleType;
				#define dirstate_tuple_check(op) (Py_TYPE(op) == &dirstateTupleType)

				#ifndef MIN
				#define MIN(a, b) (((a) < (b)) ? (a) : (b))
				#endif
				/* VC9 doesn't include bool and lacks stdbool.h based on my searching */
				#if defined(_MSC_VER) \|\| __STDC_VERSION__ < 199901L
				#define true 1
				#define false 0
				typedef unsigned char bool;
				#else
				#include <stdbool.h>
				#endif

				static inline PyObject *_dict_new_presized(Py_ssize_t expected_size)
				{
				/* _PyDict_NewPresized expects a minused parameter, but it actually
				creates a dictionary that's the nearest power of two bigger than the
				parameter. For example, with the initial minused = 1000, the
				dictionary created has size 1024. Of course in a lot of cases that
				can be greater than the maximum load factor Python's dict object
				expects (= 2/3), so as soon as we cross the threshold we'll resize
				anyway. So create a dictionary that's at least 3/2 the size. */
				return _PyDict_NewPresized(((1 + expected_size) / 2) * 3);
				}

				/* Convert a PyInt or PyLong to a long. Returns false if there is an
				error, in which case an exception will already have been set. */
				static inline bool pylong_to_long(PyObject pylong, long out)
				{
				*out = PyLong_AsLong(pylong);
				/* Fast path to avoid hitting PyErr_Occurred if the value was obviously
				* not an error. */
				if (*out != -1) {
				return true;
				}
				return PyErr_Occurred() == NULL;
				}

				#endif /* _HG_UTIL_H_ */