From: Junio C Hamano <gitster@pobox.com>
To: Jonathan Tan <jonathantanmy@google.com>
Cc: git@vger.kernel.org, stolee@gmail.com, peff@peff.net
Subject: Re: [PATCH v2 2/2] diff: restrict when prefetching occurs
Date: Thu, 02 Apr 2020 16:25:16 -0700 [thread overview]
Message-ID: <xmqqy2rd1ndv.fsf@gitster.c.googlers.com> (raw)
In-Reply-To: <20200402230937.47323-1-jonathantanmy@google.com> (Jonathan Tan's message of "Thu, 2 Apr 2020 16:09:37 -0700")
Jonathan Tan <jonathantanmy@google.com> writes:
>> This comment makes me wonder if it would be even better to
>>
>> - prepare an empty to_fetch OID array in the caller,
>>
>> - if the output format is one of the ones that wants prefetch, add
>> object names to to_fetch in the caller, BUT not fetch there.
>>
>> - pass &to_fetch by the caller to this function, and this code here
>> may add even more objects,
>>
>> - then do the prefetch here (so a single promisor interaction will
>> grab objects the caller would have fetched before calling us and
>> the ones we want here), and then clear the to_fetch array.
>>
>> - the caller, after seeing this function returns, checks to_fetch
>> and if it is not empty, fetches (i.e. the caller prepared list of
>> objects based on the output type, we ended up not calling this
>> helper, and then finally the caller does the prefetch).
>>
>> That way, the "unless we have already prefetched" logic can go, and
>> we can lose one indentation level, no?
>
> This means that the only prefetch occurs in diffcore_rename()?
No, but I phrased the last bullet item incorrectly. "after seeing
this function returns" is wrong, but what is in parentheses (i.e. if
we didn't call diffcore_rename) is correct.
> I don't
> think this will work for 2 reasons:
>
> - diffcore_std() calls diffcore_break() (which also reads blobs) before
> diffcore_rename()
Ahh, I missed that part.
> - (more importantly) there's a code path in diffcore_std() that does
> not call diffcore_rename(), so we would still need some prefetching
> logic in diffcore_std() in case diffcore_rename() is not called
That one I think is already covered.
next prev parent reply other threads:[~2020-04-02 23:25 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-31 2:04 [PATCH] diff: restrict when prefetching occurs Jonathan Tan
2020-03-31 12:14 ` Derrick Stolee
2020-03-31 16:50 ` Jonathan Tan
2020-03-31 17:48 ` Derrick Stolee
2020-03-31 18:21 ` Junio C Hamano
2020-03-31 18:15 ` Junio C Hamano
2020-04-02 19:19 ` [PATCH v2 0/2] Restrict when prefetcing occurs Jonathan Tan
2020-04-02 19:19 ` [PATCH v2 1/2] promisor-remote: accept 0 as oid_nr in function Jonathan Tan
2020-04-02 19:46 ` Junio C Hamano
2020-04-02 23:01 ` Jonathan Tan
2020-04-02 19:19 ` [PATCH v2 2/2] diff: restrict when prefetching occurs Jonathan Tan
2020-04-02 20:08 ` Junio C Hamano
2020-04-02 23:09 ` Jonathan Tan
2020-04-02 23:25 ` Junio C Hamano [this message]
2020-04-02 23:54 ` Junio C Hamano
2020-04-03 21:35 ` Jonathan Tan
2020-04-03 22:12 ` Junio C Hamano
2020-04-02 20:28 ` [PATCH v2 0/2] Restrict when prefetcing occurs Junio C Hamano
2020-04-06 11:44 ` Derrick Stolee
2020-04-06 11:57 ` Garima Singh
2020-04-07 22:11 ` [PATCH v3 0/4] " Jonathan Tan
2020-04-07 22:11 ` [PATCH v3 1/4] promisor-remote: accept 0 as oid_nr in function Jonathan Tan
2020-04-07 22:11 ` [PATCH v3 2/4] diff: make diff_populate_filespec_options struct Jonathan Tan
2020-04-07 23:44 ` Junio C Hamano
2020-04-07 22:11 ` [PATCH v3 3/4] diff: refactor object read Jonathan Tan
2020-04-07 22:11 ` [PATCH v3 4/4] diff: restrict when prefetching occurs Jonathan Tan
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