On Mon, 12 Nov 2018 10:55:47 +0100, Boris Feld wrote:
> # HG changeset patch
> # User Boris Feld <boris.f...@octobus.net>
> # Date 1541785632 -3600
> # Fri Nov 09 18:47:12 2018 +0100
> # Node ID 4a1104eade1dfb1697517d60d2c5fd7a98b8c7f0
> # Parent 0ea42453fa491793d1e145f5093b65e84cb65e97
> # EXP-Topic sparse-perf
> # Available At https://bitbucket.org/octobus/mercurial-devel/
> # hg pull https://bitbucket.org/octobus/mercurial-devel/ -r
> 4a1104eade1d
> sparse-revlog: introduce native (C) implementation of slicechunktodensity
Just quickly scanned this patch, no other patches in this series nor "sparse"
logic is reviewed.
> +struct Gap {
> + long size;
> + long idx;
> +};
> +
> +static int gap_compare(const void *left, const void *right)
> +{
> + return ((struct Gap *)left)->size - ((struct Gap *)right)->size;
> +}
> +static int long_compare(const void *left, const void *right)
> +{
> + return *(long *)left - *(long *)right;
> +}
Nit: (const <type> *)<left|right> as the argument is const void*.
If we're sure 'left - right' never exceeds the int range, it might be better
to explicitly cast the result to (int) to silence possible warning.
> +static PyObject *index_slicechunktodensity(indexObject *self, PyObject *args)
> +{
> + /* method arguments */
> + PyObject *list_revs = NULL; /* revisions in the chain */
> + double targetdensity = 0.5; /* min density to achieve */
> + long mingapsize = 0; /* threshold to ignore gaps */
> +
> + /* other core variables */
> + long i; /* used for various iteration */
> + PyObject *result = NULL; /* the final return of the function */
> +
> + /* generic information about the delta chain being slice */
> + Py_ssize_t num_revs = 0; /* size of the full delta chain */
> + Py_ssize_t *revs = NULL; /* native array of revision in the chain */
> + long chainpayload = 0; /* sum of all delta in the chain */
> + long deltachainspan = 0; /* distance from first byte to last byte */
> +
> + /* variable used for slicing the delta chain */
> + long readdata = 0; /* amount of data currently planned to be read */
> + double density = 0; /* ration of payload data compared to read ones */
> + struct Gap *gaps = NULL; /* array of notable gap in the chain */
> + long num_gaps = 0; /* total number of notable gap recorded so far */
> + Py_ssize_t *selected_indices = NULL; /* indices of gap skipped over */
> + long num_selected = 0; /* number of gaps skipped */
Maybe i, num_rgaps, num_selected should be Py_ssize_t? In general, long can
be narrower than ssize_t.
> + PyObject *chunk = NULL; /* individual slice */
> + PyObject *allchunks = PyList_New(num_selected); /* all slices */
Needs to make sure that allchunks isn't NULL.
And it's probably better to just initialize the list with literal 0, since
we have no for-loop to fill in the list items up to num_selected.
> + /* parsing argument */
> + if (!PyArg_ParseTuple(args, "O!dl", &PyList_Type, &list_revs,
> + &targetdensity, &mingapsize)) {
> + goto bail;
> + }
> +
> + /* If the delta chain contains a single element, we do not need slicing
> + */
> + num_revs = PyList_GET_SIZE(list_revs);
> + if (num_revs <= 1) {
> + result = PyTuple_Pack(1, list_revs);
> + goto done;
> + }
> +
> + /* Turn the python list into a native integer array (for efficiency) */
> + revs = (Py_ssize_t *)malloc((num_revs) * sizeof(Py_ssize_t));
num_revs * sizeof(...) can overflow. Using calloc() is safer if the zeroing
cost isn't significant.
> + if (revs == NULL) {
> + PyErr_NoMemory();
> + goto bail;
> + }
> + for (i = 0; i < num_revs; i++) {
> + Py_ssize_t revnum = PyInt_AsLong(PyList_GET_ITEM(list_revs, i));
> + if (revnum == -1 && PyErr_Occurred()) {
> + goto bail;
> + }
> + revs[i] = revnum;
> + }
Are we sure revnum is in valid range?
> +
> + /* Compute and check various property of the unsliced delta chain */
> + deltachainspan = index_segment_span(self, revs[0], revs[num_revs - 1]);
> +
> + if (deltachainspan <= mingapsize) {
> + result = PyTuple_Pack(1, list_revs);
> + goto done;
> + }
> + chainpayload = 0;
> + for (i = 0; i < num_revs; i++) {
> + chainpayload += index_get_length(self, revs[i]);
> + }
> +
> + readdata = deltachainspan;
> + density = 1.0;
> +
> + if (0 < deltachainspan) {
> + density = (double)chainpayload / (double)deltachainspan;
> + };
> +
> + if (density >= targetdensity) {
> + result = PyTuple_Pack(1, list_revs);
> + goto done;
> + }
> +
> + /* if chain is too sparse, look for relevant gaps */
> + gaps = (struct Gap *)malloc((num_revs) * sizeof(struct Gap));
This, too.
> + if (gaps == NULL) {
> + PyErr_NoMemory();
> + goto bail;
> + }
> +
> + Py_ssize_t previous_end = -1;
> + for (i = 0; i < num_revs; i++) {
> + Py_ssize_t revstart = index_get_start(self, revs[i]);
> + Py_ssize_t revsize = index_get_length(self, revs[i]);
> + if (revsize <= 0) {
> + continue;
> + }
> + if (previous_end >= 0) {
> + Py_ssize_t gapsize = revstart - previous_end;
> + if (gapsize > mingapsize) {
> + gaps[num_gaps].size = gapsize;
> + gaps[num_gaps].idx = i;
> + num_gaps += 1;
> + }
> + }
> + previous_end = revstart + revsize;
> + }
> + if (num_gaps == 0) {
> + result = PyTuple_Pack(1, list_revs);
> + goto done;
> + }
> + qsort(gaps, num_gaps, sizeof(struct Gap), &gap_compare);
> +
> + /* Slice the largest gap first, they improve the density the most */
> + selected_indices =
> + (Py_ssize_t *)malloc((num_gaps + 1) * sizeof(Py_ssize_t));
> + if (selected_indices == NULL) {
> + PyErr_NoMemory();
> + goto bail;
> + }
> +
> + for (i = num_gaps - 1; i >= 0; i--) {
> + selected_indices[num_selected] = gaps[i].idx;
> + readdata -= gaps[i].size;
> + num_selected += 1;
> + if (readdata <= 0) {
> + density = 1.0;
> + } else {
> + density = (double)chainpayload / (double)readdata;
> + }
> + if (density >= targetdensity) {
> + break;
> + }
> + }
> + qsort(selected_indices, num_selected, sizeof(Py_ssize_t),
> + &long_compare);
Py_ssize_t != long on Windows, IIRC.
> + /* create the resulting slice */
> + long previdx = 0;
> + selected_indices[num_selected] = num_revs;
> + for (i = 0; i <= num_selected; i++) {
> + long idx = selected_indices[i];
> + chunk = _trimchunk(self, list_revs, previdx, idx);
> + if (chunk == NULL) {
> + goto bail;
> + }
> + if (PyList_GET_SIZE(chunk) > 0) {
> + if (PyList_Append(allchunks, chunk) == -1) {
> + goto bail;
> + }
> + }
> + Py_DECREF(chunk);
> + chunk = NULL;
> + previdx = idx;
> + }
> + result = allchunks;
> + goto done;
> +
> +bail:
> + if (allchunks != NULL) {
> + Py_DECREF(allchunks);
> + }
> + if (chunk != NULL) {
> + Py_DECREF(chunk);
> + }
Py_XDECREF() can be used instead of != NULL.
> +done:
> + if (revs != NULL) {
> + free(revs);
> + }
> + if (gaps != NULL) {
> + free(gaps);
> + }
> + if (selected_indices != NULL) {
> + free(selected_indices);
> + }
Nit: free(NULL) is guaranteed to be noop. No need to check != NULL.
> + if (result != NULL) {
> + Py_INCREF(result);
> + }
Looks like an excessive incref as PyTuple_Pack() returns a new reference
for example.
> + return result;
> +}
_______________________________________________
Mercurial-devel mailing list
Mercurial-devel@mercurial-scm.org
https://www.mercurial-scm.org/mailman/listinfo/mercurial-devel
