From: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
To: Eric Wong <e@80x24.org>
Cc: git@vger.kernel.org
Subject: Re: [PATCH] delta-islands: free island-related data after use
Date: Wed, 16 Nov 2022 16:44:31 +0100 [thread overview]
Message-ID: <221116.861qq2kieu.gmgdl@evledraar.gmail.com> (raw)
In-Reply-To: <20221116105013.1777440-1-e@80x24.org>
On Wed, Nov 16 2022, Eric Wong wrote:
> 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.
> 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)
next prev parent reply other threads:[~2022-11-16 15:51 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-16 10:50 [PATCH] delta-islands: free island-related data after use Eric Wong
2022-11-16 15:44 ` Ævar Arnfjörð Bjarmason [this message]
2022-11-17 23:06 ` [PATCH v2] " Eric Wong
2022-11-18 1:51 ` Ævar Arnfjörð Bjarmason
2022-11-22 20:22 ` Jeff King
2022-11-16 18:44 ` [PATCH] " Jeff King
2023-02-01 9:20 ` pack-objects memory use observations [was: [PATCH] delta-islands: free island-related data after use] Eric Wong
2023-02-01 22:09 ` Eric Wong
2023-02-02 0:11 ` Jeff King
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