Re: [PATCH v7 00/13] nd/pack-objects-pack-struct updates
- From
Jeff King <peff@peff.net>
- Date
- Mar 26, 2018, 15:13 UTC
- Message-ID
- <20180326151317.GA24425@sigill.intra.peff.net>
- In-Reply-To
- <20180324063353.24722-1-pclouds@gmail.com>
On Sat, Mar 24, 2018 at 07:33:40AM +0100, Nguyễn Thái Ngọc Duy wrote:
Show 34 quoted lines
> +unsigned long oe_get_size_slow(struct packing_data *pack,
> + const struct object_entry *e)
> +{
> + struct packed_git *p;
> + struct pack_window *w_curs;
> + unsigned char *buf;
> + enum object_type type;
> + unsigned long used, avail, size;
> +
> + if (e->type_ != OBJ_OFS_DELTA && e->type_ != OBJ_REF_DELTA) {
> + read_lock();
> + if (sha1_object_info(e->idx.oid.hash, &size) < 0)
> + die(_("unable to get size of %s"),
> + oid_to_hex(&e->idx.oid));
> + read_unlock();
> + return size;
> + }
> +
> + p = oe_in_pack(pack, e);
> + if (!p)
> + die("BUG: when e->type is a delta, it must belong to a pack");
> +
> + read_lock();
> + w_curs = NULL;
> + buf = use_pack(p, &w_curs, e->in_pack_offset, &avail);
> + used = unpack_object_header_buffer(buf, avail, &type, &size);
> + if (used == 0)
> + die(_("unable to parse object header of %s"),
> + oid_to_hex(&e->idx.oid));
> +
> + unuse_pack(&w_curs);
> + read_unlock();
> + return size;
> +}It took me a while to figure out why this treated deltas and non-deltas differently. At first I thought it was an optimization (since we can find non-delta sizes quickly by looking at the headers). But I think it's just that you want to know the size of the actual _delta_, not the reconstructed object. And there's no way to ask sha1_object_info() for that.
Perhaps the _extended version of that function should learn an OBJECT_INFO_NO_DEREF flag or something to tell it return the true delta type and size. Then this whole function could just become a single call.
But short of that, it's probably worth a comment explaining what's going on.
Show 12 quoted lines
> +static void prepare_in_pack_by_idx(struct packing_data *pdata)
> +{
> + struct packed_git **mapping, *p;
> + int cnt = 0, nr = 1 << OE_IN_PACK_BITS;
> +
> + if (getenv("GIT_TEST_FULL_IN_PACK_ARRAY")) {
> + /*
> + * leave in_pack_by_idx NULL to force in_pack[] to be
> + * used instead
> + */
> + return;
> + }Minor nit, but can we use git_env_bool() here? It's just as easy, and it's less surprising in some corner cases.
Show 15 quoted lines
> struct object_entry *packlist_alloc(struct packing_data *pdata,
> const unsigned char *sha1,
> uint32_t index_pos)
> {
> struct object_entry *new_entry;
>
> + if (!pdata->nr_objects) {
> + prepare_in_pack_by_idx(pdata);
> + if (getenv("GIT_TEST_OE_SIZE_BITS")) {
> + int bits = atoi(getenv("GIT_TEST_OE_SIZE_BITS"));;
> + pdata->oe_size_limit = 1 << bits;
> + }
> + if (!pdata->oe_size_limit)
> + pdata->oe_size_limit = 1 << OE_SIZE_BITS;
> + }Ditto here; I think this could just be:
pdata->oe_size_limit = git_env_ulong("GIT_TEST_OE_SIZE_BITS",
(1 << OE_SIZE_BITS));Show 7 quoted lines
> if (pdata->nr_objects >= pdata->nr_alloc) {
> pdata->nr_alloc = (pdata->nr_alloc + 1024) * 3 / 2;
> REALLOC_ARRAY(pdata->objects, pdata->nr_alloc);
> +
> + if (!pdata->in_pack_by_idx)
> + REALLOC_ARRAY(pdata->in_pack, pdata->nr_alloc);
> }I was going to complain that we don't use ALLOC_GROW() here, but actually that part is in the context. ;)
Show 8 quoted lines
> @@ -35,7 +36,9 @@ enum dfs_state {
> *
> * "size" is the uncompressed object size. Compressed size of the raw
> * data for an object in a pack is not stored anywhere but is computed
> - * and made available when reverse .idx is made.
> + * and made available when reverse .idx is made. Note that when an
> + * delta is reused, "size" is the uncompressed _delta_ size, not the
> + * canonical one after the delta has been applied.s/an delta/a delta/
Show 19 quoted lines
> +Running tests with special setups > +--------------------------------- > + > +The whole test suite could be run to test some special features > +that cannot be easily covered by a few specific test cases. These > +could be enabled by running the test suite with correct GIT_TEST_ > +environment set. > + > +GIT_TEST_SPLIT_INDEX forces split-index mode on the whole test suite. > + > +GIT_TEST_FULL_IN_PACK_ARRAY exercises the uncommon pack-objects code > +path where there are more than 1024 packs even if the actual number of > +packs in repository is below this limit. > + > +GIT_TEST_OE_SIZE_BITS=<bits> exercises the uncommon pack-objects > +code path where we do not cache objecct size in memory and read it > +from existing packs on demand. This normally only happens when the > +object size is over 2GB. This variable forces the code path on any > +object larger than 2^<bits> bytes.
It's nice to have these available to test the uncommon cases. But I have a feeling nobody will ever run them, since it requires extra effort (and takes a full test run).
I see there's a one-off test for GIT_TEST_FULL_IN_PACK_ARRAY, which I think is a good idea, since it makes sure the code is exercised in a normal test suite run. Should we do the same for GIT_TEST_OE_SIZE_BITS?
Also, s/objecct/object/. :)
> [...]
I haven't done an in-depth read of each patch yet; this was just what jumped out at me from reading the interdiff.
-Peff