Re: [PATCH] delta-islands: free island-related data after use
- From
Ævar Arnfjörð Bjarmason <avarab@gmail.com>
- Date
- Nov 16, 2022, 15:44 UTC
- Message-ID
- <221116.861qq2kieu.gmgdl@evledraar.gmail.com>
- In-Reply-To
- <20221116105013.1777440-1-e@80x24.org>
On Wed, Nov 16 2022, Eric Wong wrote:
Show 17 quoted lines
> On my use case involving 771 islands of Linux on kernel.org, > this reduces memory usage by around 25MB. The bulk of that > comes from free_remote_islands, since free_island_regexes only > saves around 40k. > > This memory is saved early in the memory-intensive pack process, > making it available for the remainder of the long process. > > Signed-off-by: Eric Wong <e@80x24.org> > --- > Note: I only noticed this when I screwed up up a pack.island RE, > ended up with hundreds of thousands of islands instead of 771, > and kept OOM-ing :x > > Memory savings were measured using the following patch which > relies on a patched LD_PRELOAD-based malloc debugger: > https://80x24.org/spew/20221116095404.3974691-1-e@80x24.org/raw
FWIW SANITIZE=leak will find this if you stick a "remote_islands = NULL" and run e.g. t5320-delta-islands.sh, but maybe you needed this closer to production.
Valgrind will also work, but of course be *much* slower.
Show 51 quoted lines
> Will try to hunt down more memory savings in the nearish future.
>
> delta-islands.c | 27 +++++++++++++++++++++++++++
> 1 file changed, 27 insertions(+)
>
> diff --git a/delta-islands.c b/delta-islands.c
> index 26f9e99e1a..391e947cc6 100644
> --- a/delta-islands.c
> +++ b/delta-islands.c
> @@ -454,6 +454,31 @@ static void deduplicate_islands(struct repository *r)
> free(list);
> }
>
> +static void free_island_regexes(void)
> +{
> + unsigned int i;
> +
> + for (i = 0; i < island_regexes_nr; i++)
> + regfree(&island_regexes[i]);
> +
> + FREE_AND_NULL(island_regexes);
> + island_regexes_alloc = island_regexes_nr = 0;
> +}
> +
> +static void free_remote_islands(void)
> +{
> + const char *island_name;
> + struct remote_island *rl;
> +
> + kh_foreach(remote_islands, island_name, rl, {
> + free((void *)island_name);
> + oid_array_clear(&rl->oids);
> + free(rl);
> + });
> + kh_destroy_str(remote_islands);
> + remote_islands = NULL;
> +}
> +
> void load_delta_islands(struct repository *r, int progress)
> {
> island_marks = kh_init_oid_map();
> @@ -461,7 +486,9 @@ void load_delta_islands(struct repository *r, int progress)
>
> git_config(island_config_callback, NULL);
> for_each_ref(find_island_for_ref, NULL);
> + free_island_regexes();
> deduplicate_islands(r);
> + free_remote_islands();
>
> if (progress)
> fprintf(stderr, _("Marked %d islands, done.\n"), island_counter);Perfect shouldn't be the enemy of the good & all that, but in this case it's not too much more effort to just give this data an appropriate lifetime instead of the global, I tried that out for just the "regex" part of this below.
The free_remote_islands() seems to be similarly alive between "find_island_for_ref" and "deduplicate_islands".
Your version also works, but the root cause of this sort of thing is these global lifetimes, which sometimes we do for a good reason, but in this case we don't.
It's more lines, but e.g. your FREE_AND_NULL() and resetting "nr" and "alloc" makes one wonder how the data might be used outside fo that load_delta_islands() chain (which is needed, if we invoke it again), when we can just init a stack variable to hold it instead...
diff --git a/delta-islands.c b/delta-islands.c index 26f9e99e1a9..ef86a91059c 100644 --- a/delta-islands.c +++ b/delta-islands.c @@ -312,29 +312,41 @@ void resolve_tree_islands(struct repository *r, free(todo); } -static regex_t *island_regexes; -static unsigned int island_regexes_alloc, island_regexes_nr; +struct island_config_data { + regex_t *rx; + size_t nr; + size_t alloc; +}; static const char *core_island_name; -static int island_config_callback(const char *k, const char *v, void *cb UNUSED) +static void island_config_data_release(struct island_config_data *icd) +{ + for (size_t i = 0; i < icd->nr; i++) + regfree(&icd->rx[i]); + free(icd->rx); +} + +static int island_config_callback(const char *k, const char *v, void *cb) { + struct island_config_data *data = cb; + if (!strcmp(k, "pack.island")) { struct strbuf re = STRBUF_INIT; if (!v) return config_error_nonbool(k); - ALLOC_GROW(island_regexes, island_regexes_nr + 1, island_regexes_alloc); + ALLOC_GROW(data->rx, data->nr + 1, data->alloc); if (*v != '^') strbuf_addch(&re, '^'); strbuf_addstr(&re, v); - if (regcomp(&island_regexes[island_regexes_nr], re.buf, REG_EXTENDED)) + if (regcomp(&data->rx[data->nr], re.buf, REG_EXTENDED)) die(_("failed to load island regex for '%s': %s"), k, re.buf); strbuf_release(&re); - island_regexes_nr++; + data->nr++; return 0; } @@ -365,8 +377,10 @@ static void add_ref_to_island(const char *island_name, const struct object_id *o } static int find_island_for_ref(const char *refname, const struct object_id *oid, - int flags UNUSED, void *data UNUSED) + int flags UNUSED, void *cb) { + struct island_config_data *data = cb; + /* * We should advertise 'ARRAY_SIZE(matches) - 2' as the max, * so we can diagnose below a config with more capture groups @@ -377,8 +391,8 @@ static int find_island_for_ref(const char *refname, const struct object_id *oid, struct strbuf island_name = STRBUF_INIT; /* walk backwards to get last-one-wins ordering */ - for (i = island_regexes_nr - 1; i >= 0; i--) { - if (!regexec(&island_regexes[i], refname, + for (i = data->nr - 1; i >= 0; i--) { + if (!regexec(&data->rx[i], refname, ARRAY_SIZE(matches), matches, 0)) break; } @@ -456,11 +470,14 @@ static void deduplicate_islands(struct repository *r) void load_delta_islands(struct repository *r, int progress) { + struct island_config_data data = { 0 }; + island_marks = kh_init_oid_map(); remote_islands = kh_init_str(); - git_config(island_config_callback, NULL); - for_each_ref(find_island_for_ref, NULL); + git_config(island_config_callback, &data); + for_each_ref(find_island_for_ref, &data); + island_config_data_release(&data); deduplicate_islands(r); if (progress)