From: Jonathan Nieder <jrnieder@gmail.com>
To: Jonathan Tan <jonathantanmy@google.com>
Cc: git@vger.kernel.org, peff@peff.net, gitster@pobox.com
Subject: Re: [PATCH 1/2] fetch-pack: in protocol v2, in_vain only after ACK
Date: Sat, 25 Apr 2020 17:28:02 -0700 [thread overview]
Message-ID: <20200426002802.GD877@gmail.com> (raw)
In-Reply-To: <51174e53527f9b29bb0a5ebb8726f07333113dfb.1587775989.git.jonathantanmy@google.com>
Hi,
Jonathan Tan wrote:
> When fetching, Git stops negotiation when it has sent at least
> MAX_IN_VAIN (which is 256) "have" lines without having any of them
> ACK-ed. But this is supposed to trigger only after the first ACK, as
> pack-protocol.txt says:
>
> However, the 256 limit *only* turns on in the canonical client
> implementation if we have received at least one "ACK %s continue"
> during a prior round. This helps to ensure that at least one common
> ancestor is found before we give up entirely.
>
> The code path for protocol v0 observes this, but not protocol v2,
> resulting in shorter negotiation rounds but significantly larger
> packfiles. Teach the code path for protocol v2 to check this criterion
> only after at least one ACK was received.
>
> Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
> ---
> fetch-pack.c | 13 +++++++++----
> t/t5500-fetch-pack.sh | 19 +++++++++++++++++++
> 2 files changed, 28 insertions(+), 4 deletions(-)
Makes a lot of sense. Good find.
[...]
> --- a/fetch-pack.c
> +++ b/fetch-pack.c
[...]
> @@ -1513,6 +1517,7 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
> break;
> case 1:
> in_vain = 0;
> + seen_ack = 1;
not about this patch: can these return values from process_acks be made
into an enum with named enumerators? That would make what's happening
in the call site more obvious.
> /* fallthrough */
> default:
> state = FETCH_SEND_REQUEST;
> diff --git a/t/t5500-fetch-pack.sh b/t/t5500-fetch-pack.sh
> index baa1a99f45..fcc5cc8ab0 100755
> --- a/t/t5500-fetch-pack.sh
> +++ b/t/t5500-fetch-pack.sh
> @@ -385,6 +385,25 @@ test_expect_success 'clone shallow with packed refs' '
> test_cmp count8.expected count8.actual
> '
>
> +test_expect_success 'in_vain not triggered before first ACK' '
> + rm -rf myserver myclient trace &&
> + git init myserver &&
> + test_commit -C myserver foo &&
> + git clone "file://$(pwd)/myserver" myclient &&
> +
> + # MAX_IN_VAIN is 256. Because of batching, the client will send 496
> + # (16+32+64+128+256) commits, not 256, before giving up. So create 496
> + # irrelevant commits.
> + test_commit_bulk -C myclient 496 &&
> +
> + # The new commit that the client wants to fetch.
> + test_commit -C myserver bar &&
> +
> + GIT_TRACE_PACKET="$(pwd)/trace" git -C myclient fetch --progress origin &&
> + cp trace /tmp/x &&
Leftover debugging line?
> + test_i18ngrep "Total 3 " trace
Clever.
In some sense this is a fragile test, since the server could change
how it reports progress some day. Would it make sense (perhaps as a
followup patch) for this to use a trace2 log instead? For example,
if we turn on tracing in the server, then since 9ed8790282
(pack-objects: write objects packed to trace2, 2019-04-11) it will
report how many objects were in the pack it wrote.
After removing the "cp trace /tmp/x" line,
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Thanks.
next prev parent reply other threads:[~2020-04-26 0:28 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-25 0:56 [PATCH 0/2] Protocol v2 in_vain fixes Jonathan Tan
2020-04-25 0:56 ` [PATCH 1/2] fetch-pack: in protocol v2, in_vain only after ACK Jonathan Tan
2020-04-25 5:08 ` Junio C Hamano
2020-04-26 0:28 ` Jonathan Nieder [this message]
2020-04-27 17:27 ` Jonathan Tan
2020-04-27 22:16 ` Junio C Hamano
2020-04-25 0:56 ` [PATCH 2/2] fetch-pack: in protocol v2, reset in_vain upon ACK Jonathan Tan
2020-04-26 1:10 ` Jonathan Nieder
2020-04-27 17:28 ` Jonathan Tan
2020-04-28 0:01 ` [PATCH v2 0/3] Protocol v2 in_vain fixes Jonathan Tan
2020-04-28 0:01 ` [PATCH v2 1/3] fetch-pack: return enum from process_acks() Jonathan Tan
2020-04-28 0:53 ` Jonathan Nieder
2020-04-28 16:54 ` Junio C Hamano
2020-04-28 18:00 ` Michal Suchánek
2020-04-28 19:17 ` Junio C Hamano
2020-04-28 0:01 ` [PATCH v2 2/3] fetch-pack: in protocol v2, in_vain only after ACK Jonathan Tan
2020-04-28 0:54 ` Jonathan Nieder
2020-05-06 21:08 ` Johannes Schindelin
2020-05-06 22:07 ` [PATCH] t5500: count objects through stderr, not trace Jonathan Tan
2020-05-06 22:28 ` Junio C Hamano
2020-05-06 22:40 ` Junio C Hamano
2020-05-07 14:35 ` Johannes Schindelin
2020-10-13 14:45 ` Johannes Schindelin
2020-04-28 0:01 ` [PATCH v2 3/3] fetch-pack: in protocol v2, reset in_vain upon ACK Jonathan Tan
2020-04-28 0:55 ` Jonathan Nieder
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