git/connected.h

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#ifndef CONNECTED_H
#define CONNECTED_H
struct object_id;
clone: open a shortcut for connectivity check In order to make sure the cloned repository is good, we run "rev-list --objects --not --all $new_refs" on the repository. This is expensive on large repositories. This patch attempts to mitigate the impact in this special case. In the "good" clone case, we only have one pack. If all of the following are met, we can be sure that all objects reachable from the new refs exist, which is the intention of running "rev-list ...": - all refs point to an object in the pack - there are no dangling pointers in any object in the pack - no objects in the pack point to objects outside the pack The second and third checks can be done with the help of index-pack as a slight variation of --strict check (which introduces a new condition for the shortcut: pack transfer must be used and the number of objects large enough to call index-pack). The first is checked in check_everything_connected after we get an "ok" from index-pack. "index-pack + new checks" is still faster than the current "index-pack + rev-list", which is the whole point of this patch. If any of the conditions fail, we fall back to the good old but expensive "rev-list ..". In that case it's even more expensive because we have to pay for the new checks in index-pack. But that should only happen when the other side is either buggy or malicious. Cloning linux-2.6 over file:// before after real 3m25.693s 2m53.050s user 5m2.037s 4m42.396s sys 0m13.750s 0m16.574s A more realistic test with ssh:// over wireless before after real 11m26.629s 10m4.213s user 5m43.196s 5m19.444s sys 0m35.812s 0m37.630s This shortcut is not applied to shallow clones, partly because shallow clones should have no more objects than a usual fetch and the cost of rev-list is acceptable, partly to avoid dealing with corner cases when grafting is involved. This shortcut does not apply to unpack-objects code path either because the number of objects must be small in order to trigger that code path. Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-05-26 01:16:17 +00:00
struct transport;
/*
* Take callback data, and return next object name in the buffer.
* When called after returning the name for the last object, return -1
* to signal EOF, otherwise return 0.
*/
connected: refactor iterator to return next object ID directly The object ID iterator used by the connectivity checks returns the next object ID via an out-parameter and then uses a return code to indicate whether an item was found. This is a bit roundabout: instead of a separate error code, we can just return the next object ID directly and use `NULL` pointers as indicator that the iterator got no items left. Furthermore, this avoids a copy of the object ID. Refactor the iterator and all its implementations to return object IDs directly. This brings a tiny performance improvement when doing a mirror-fetch of a repository with about 2.3M refs: Benchmark #1: 328dc58b49919c43897240f2eabfa30be2ce32a4~: git-fetch Time (mean ± σ): 30.110 s ± 0.148 s [User: 27.161 s, System: 5.075 s] Range (min … max): 29.934 s … 30.406 s 10 runs Benchmark #2: 328dc58b49919c43897240f2eabfa30be2ce32a4: git-fetch Time (mean ± σ): 29.899 s ± 0.109 s [User: 26.916 s, System: 5.104 s] Range (min … max): 29.696 s … 29.996 s 10 runs Summary '328dc58b49919c43897240f2eabfa30be2ce32a4: git-fetch' ran 1.01 ± 0.01 times faster than '328dc58b49919c43897240f2eabfa30be2ce32a4~: git-fetch' While this 1% speedup could be labelled as statistically insignificant, the speedup is consistent on my machine. Furthermore, this is an end to end test, so it is expected that the improvement in the connectivity check itself is more significant. Signed-off-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-09-01 13:09:50 +00:00
typedef const struct object_id *(*oid_iterate_fn)(void *);
check_everything_connected: use a struct with named options The number of variants of check_everything_connected has grown over the years, so that the "real" function takes several possibly-zero, possibly-NULL arguments. We hid the complexity behind some wrapper functions, but this doesn't scale well when we want to add new options. If we add more wrapper variants to handle the new options, then we can get a combinatorial explosion when those options might be used together (right now nobody wants to use both "shallow" and "transport" together, so we get by with just a few wrappers). If instead we add new parameters to each function, each of which can have a default value, then callers who want the defaults end up with confusing invocations like: check_everything_connected(fn, 0, data, -1, 0, NULL); where it is unclear which parameter is which (and every caller needs updated when we add new options). Instead, let's add a struct to hold all of the optional parameters. This is a little more verbose for the callers (who have to declare the struct and fill it in), but it makes their code much easier to follow, because every option is named as it is set (and unused options do not have to be mentioned at all). Note that we could also stick the iteration function and its callback data into the option struct, too. But since those are required for each call, by avoiding doing so, we can let very simple callers just pass "NULL" for the options and not worry about the struct at all. While we're touching each site, let's also rename the function to check_connected(). The existing name was quite long, and not all of the wrappers even used the full name. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2016-07-15 10:30:40 +00:00
/*
* Named-arguments struct for check_connected. All arguments are
* optional, and can be left to defaults as set by CHECK_CONNECTED_INIT.
*/
struct check_connected_options {
/* Avoid printing any errors to stderr. */
int quiet;
/* --shallow-file to pass to rev-list sub-process */
const char *shallow_file;
/* Transport whose objects we are checking, if available. */
struct transport *transport;
/*
* If non-zero, send error messages to this descriptor rather
* than stderr. The descriptor is closed before check_connected
* returns.
*/
int err_fd;
/* If non-zero, show progress as we traverse the objects. */
int progress;
/*
* Insert these variables into the environment of the child process.
*/
const char **env;
fetch-pack: write shallow, then check connectivity When fetching, connectivity is checked after the shallow file is updated. There are 2 issues with this: (1) the connectivity check is only performed up to ancestors of existing refs (which is not thorough enough if we were deepening an existing ref in the first place), and (2) there is no rollback of the shallow file if the connectivity check fails. To solve (1), update the connectivity check to check the ancestry chain completely in the case of a deepening fetch by refraining from passing "--not --all" when invoking rev-list in connected.c. To solve (2), have fetch_pack() perform its own connectivity check before updating the shallow file. To support existing use cases in which "git fetch-pack" is used to download objects without much regard as to the connectivity of the resulting objects with respect to the existing repository, the connectivity check is only done if necessary (that is, the fetch is not a clone, and the fetch involves shallow/deepen functionality). "git fetch" still performs its own connectivity check, preserving correctness but sometimes performing redundant work. This redundancy is mitigated by the fact that fetch_pack() reports if it has performed a connectivity check itself, and if the transport supports connect or stateless-connect, it will bubble up that report so that "git fetch" knows not to perform the connectivity check in such a case. This was noticed when a user tried to deepen an existing repository by fetching with --no-shallow from a server that did not send all necessary objects - the connectivity check as run by "git fetch" succeeded, but a subsequent "git fsck" failed. Signed-off-by: Jonathan Tan <jonathantanmy@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2018-07-02 22:08:43 +00:00
/*
* If non-zero, check the ancestry chain completely, not stopping at
* any existing ref. This is necessary when deepening existing refs
* during a fetch.
*/
unsigned is_deepening_fetch : 1;
receive-pack: only use visible refs for connectivity check When serving a push, git-receive-pack(1) needs to verify that the packfile sent by the client contains all objects that are required by the updated references. This connectivity check works by marking all preexisting references as uninteresting and using the new reference tips as starting point for a graph walk. Marking all preexisting references as uninteresting can be a problem when it comes to performance. Git forges tend to do internal bookkeeping to keep alive sets of objects for internal use or make them easy to find via certain references. These references are typically hidden away from the user so that they are neither advertised nor writeable. At GitLab, we have one particular repository that contains a total of 7 million references, of which 6.8 million are indeed internal references. With the current connectivity check we are forced to load all these references in order to mark them as uninteresting, and this alone takes around 15 seconds to compute. We can optimize this by only taking into account the set of visible refs when marking objects as uninteresting. This means that we may now walk more objects until we hit any object that is marked as uninteresting. But it is rather unlikely that clients send objects that make large parts of objects reachable that have previously only ever been hidden, whereas the common case is to push incremental changes that build on top of the visible object graph. This provides a huge boost to performance in the mentioned repository, where the vast majority of its refs hidden. Pushing a new commit into this repo with `transfer.hideRefs` set up to hide 6.8 million of 7 refs as it is configured in Gitaly leads to a 4.5-fold speedup: Benchmark 1: main Time (mean ± σ): 30.977 s ± 0.157 s [User: 30.226 s, System: 1.083 s] Range (min … max): 30.796 s … 31.071 s 3 runs Benchmark 2: pks-connectivity-check-hide-refs Time (mean ± σ): 6.799 s ± 0.063 s [User: 6.803 s, System: 0.354 s] Range (min … max): 6.729 s … 6.850 s 3 runs Summary 'pks-connectivity-check-hide-refs' ran 4.56 ± 0.05 times faster than 'main' As we mostly go through the same codepaths even in the case where there are no hidden refs at all compared to the code before there is no change in performance when no refs are hidden: Benchmark 1: main Time (mean ± σ): 48.188 s ± 0.432 s [User: 49.326 s, System: 5.009 s] Range (min … max): 47.706 s … 48.539 s 3 runs Benchmark 2: pks-connectivity-check-hide-refs Time (mean ± σ): 48.027 s ± 0.500 s [User: 48.934 s, System: 5.025 s] Range (min … max): 47.504 s … 48.500 s 3 runs Summary 'pks-connectivity-check-hide-refs' ran 1.00 ± 0.01 times faster than 'main' Signed-off-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Taylor Blau <me@ttaylorr.com>
2022-11-17 05:47:04 +00:00
/*
* If not NULL, use `--exclude-hidden=$section` to exclude all refs
* hidden via the `$section.hideRefs` config from the set of
* already-reachable refs.
*/
const char *exclude_hidden_refs_section;
check_everything_connected: use a struct with named options The number of variants of check_everything_connected has grown over the years, so that the "real" function takes several possibly-zero, possibly-NULL arguments. We hid the complexity behind some wrapper functions, but this doesn't scale well when we want to add new options. If we add more wrapper variants to handle the new options, then we can get a combinatorial explosion when those options might be used together (right now nobody wants to use both "shallow" and "transport" together, so we get by with just a few wrappers). If instead we add new parameters to each function, each of which can have a default value, then callers who want the defaults end up with confusing invocations like: check_everything_connected(fn, 0, data, -1, 0, NULL); where it is unclear which parameter is which (and every caller needs updated when we add new options). Instead, let's add a struct to hold all of the optional parameters. This is a little more verbose for the callers (who have to declare the struct and fill it in), but it makes their code much easier to follow, because every option is named as it is set (and unused options do not have to be mentioned at all). Note that we could also stick the iteration function and its callback data into the option struct, too. But since those are required for each call, by avoiding doing so, we can let very simple callers just pass "NULL" for the options and not worry about the struct at all. While we're touching each site, let's also rename the function to check_connected(). The existing name was quite long, and not all of the wrappers even used the full name. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2016-07-15 10:30:40 +00:00
};
#define CHECK_CONNECTED_INIT { 0 }
/*
* Make sure that all given objects and all objects reachable from them
* either exist in our object store or (if the repository is a partial
* clone) are promised to be available.
*
* Return 0 if Ok, non zero otherwise (i.e. some missing objects)
check_everything_connected: use a struct with named options The number of variants of check_everything_connected has grown over the years, so that the "real" function takes several possibly-zero, possibly-NULL arguments. We hid the complexity behind some wrapper functions, but this doesn't scale well when we want to add new options. If we add more wrapper variants to handle the new options, then we can get a combinatorial explosion when those options might be used together (right now nobody wants to use both "shallow" and "transport" together, so we get by with just a few wrappers). If instead we add new parameters to each function, each of which can have a default value, then callers who want the defaults end up with confusing invocations like: check_everything_connected(fn, 0, data, -1, 0, NULL); where it is unclear which parameter is which (and every caller needs updated when we add new options). Instead, let's add a struct to hold all of the optional parameters. This is a little more verbose for the callers (who have to declare the struct and fill it in), but it makes their code much easier to follow, because every option is named as it is set (and unused options do not have to be mentioned at all). Note that we could also stick the iteration function and its callback data into the option struct, too. But since those are required for each call, by avoiding doing so, we can let very simple callers just pass "NULL" for the options and not worry about the struct at all. While we're touching each site, let's also rename the function to check_connected(). The existing name was quite long, and not all of the wrappers even used the full name. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2016-07-15 10:30:40 +00:00
*
* If "opt" is NULL, behaves as if CHECK_CONNECTED_INIT was passed.
*/
int check_connected(oid_iterate_fn fn, void *cb_data,
check_everything_connected: use a struct with named options The number of variants of check_everything_connected has grown over the years, so that the "real" function takes several possibly-zero, possibly-NULL arguments. We hid the complexity behind some wrapper functions, but this doesn't scale well when we want to add new options. If we add more wrapper variants to handle the new options, then we can get a combinatorial explosion when those options might be used together (right now nobody wants to use both "shallow" and "transport" together, so we get by with just a few wrappers). If instead we add new parameters to each function, each of which can have a default value, then callers who want the defaults end up with confusing invocations like: check_everything_connected(fn, 0, data, -1, 0, NULL); where it is unclear which parameter is which (and every caller needs updated when we add new options). Instead, let's add a struct to hold all of the optional parameters. This is a little more verbose for the callers (who have to declare the struct and fill it in), but it makes their code much easier to follow, because every option is named as it is set (and unused options do not have to be mentioned at all). Note that we could also stick the iteration function and its callback data into the option struct, too. But since those are required for each call, by avoiding doing so, we can let very simple callers just pass "NULL" for the options and not worry about the struct at all. While we're touching each site, let's also rename the function to check_connected(). The existing name was quite long, and not all of the wrappers even used the full name. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2016-07-15 10:30:40 +00:00
struct check_connected_options *opt);
#endif /* CONNECTED_H */