From: Patrick Steinhardt <ps@pks.im>
To: git@vger.kernel.org
Subject: [PATCH] ls-refs: reuse buffer when sending refs
Date: Wed, 25 Aug 2021 15:49:51 +0200 [thread overview]
Message-ID: <ccd03e685af0f5cf25c68272a758fc88d115e37a.1629899211.git.ps@pks.im> (raw)
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In the initial reference advertisement, the Git server will first
announce all of its references to the client. The logic is handled in
`send_ref()`, which will allocate a new buffer for each refline it is
about to send. This is quite wasteful: instead of allocating a new
buffer each time, we can just reuse a buffer.
Improve this by passing in a buffer via the `ls_refs_data` struct which
is then reused on each reference. In a repository with about 2.3M refs,
this speeds up local mirror fetches by about 2%:
Benchmark #1: HEAD~: git-fetch
Time (mean ± σ): 25.415 s ± 0.131 s [User: 22.722 s, System: 4.740 s]
Range (min … max): 25.240 s … 25.543 s 5 runs
Benchmark #2: HEAD: git-fetch
Time (mean ± σ): 24.922 s ± 0.110 s [User: 22.404 s, System: 4.476 s]
Range (min … max): 24.825 s … 25.081 s 5 runs
Summary
'HEAD: git-fetch' ran
1.02 ± 0.01 times faster than 'HEAD~: git-fetch'
Signed-off-by: Patrick Steinhardt <ps@kps.im>
---
Note that while this topic applies on top of "master", I've done the
benchmark on top of my other optimizations for fetches. It's cheating a
bit, but it's easier to see that the optimization does something when
the remaining constant part is lower.
ls-refs.c | 19 +++++++++++--------
1 file changed, 11 insertions(+), 8 deletions(-)
diff --git a/ls-refs.c b/ls-refs.c
index 88f6c3f60d..84021416ca 100644
--- a/ls-refs.c
+++ b/ls-refs.c
@@ -65,6 +65,7 @@ struct ls_refs_data {
unsigned peel;
unsigned symrefs;
struct strvec prefixes;
+ struct strbuf buf;
unsigned unborn : 1;
};
@@ -73,7 +74,8 @@ static int send_ref(const char *refname, const struct object_id *oid,
{
struct ls_refs_data *data = cb_data;
const char *refname_nons = strip_namespace(refname);
- struct strbuf refline = STRBUF_INIT;
+
+ strbuf_reset(&data->buf);
if (ref_is_hidden(refname_nons, refname))
return 0;
@@ -82,9 +84,9 @@ static int send_ref(const char *refname, const struct object_id *oid,
return 0;
if (oid)
- strbuf_addf(&refline, "%s %s", oid_to_hex(oid), refname_nons);
+ strbuf_addf(&data->buf, "%s %s", oid_to_hex(oid), refname_nons);
else
- strbuf_addf(&refline, "unborn %s", refname_nons);
+ strbuf_addf(&data->buf, "unborn %s", refname_nons);
if (data->symrefs && flag & REF_ISSYMREF) {
struct object_id unused;
const char *symref_target = resolve_ref_unsafe(refname, 0,
@@ -94,20 +96,19 @@ static int send_ref(const char *refname, const struct object_id *oid,
if (!symref_target)
die("'%s' is a symref but it is not?", refname);
- strbuf_addf(&refline, " symref-target:%s",
+ strbuf_addf(&data->buf, " symref-target:%s",
strip_namespace(symref_target));
}
if (data->peel && oid) {
struct object_id peeled;
if (!peel_iterated_oid(oid, &peeled))
- strbuf_addf(&refline, " peeled:%s", oid_to_hex(&peeled));
+ strbuf_addf(&data->buf, " peeled:%s", oid_to_hex(&peeled));
}
- strbuf_addch(&refline, '\n');
- packet_write(1, refline.buf, refline.len);
+ strbuf_addch(&data->buf, '\n');
+ packet_write(1, data->buf.buf, data->buf.len);
- strbuf_release(&refline);
return 0;
}
@@ -145,6 +146,7 @@ int ls_refs(struct repository *r, struct strvec *keys,
memset(&data, 0, sizeof(data));
strvec_init(&data.prefixes);
+ strbuf_init(&data.buf, 0);
ensure_config_read();
git_config(ls_refs_config, NULL);
@@ -173,6 +175,7 @@ int ls_refs(struct repository *r, struct strvec *keys,
send_ref, &data, 0);
packet_flush(1);
strvec_clear(&data.prefixes);
+ strbuf_release(&data.buf);
return 0;
}
--
2.33.0
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next reply other threads:[~2021-08-25 13:50 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-25 13:49 Patrick Steinhardt [this message]
2021-08-25 14:10 ` [PATCH] ls-refs: reuse buffer when sending refs Patrick Steinhardt
2021-08-25 14:50 ` Derrick Stolee
2021-08-25 15:43 ` Patrick Steinhardt
2021-08-25 17:23 ` Junio C Hamano
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