Re: [PATCH 2/2] pack-objects: prefetch objects to be packed

From: Jonathan Tan <jonathantanmy@google.com>
Date: Jul 21, 2020, 23:37 UTC
Message-ID: <20200721233707.1363438-1-jonathantanmy@google.com>
In-Reply-To: <xmqqh7u07e41.fsf@gitster.c.googlers.com>

Show 18 quoted lines

> Junio C Hamano <gitster@pobox.com> writes:
> 
> >>> The optimization makes sense to me if certain
> >>> conditions are met, like...
> >>> 
> >>>  - Most of the time there is no missing object due to promisor, even
> >>>    if has_promissor_to_remote() is true;
> >>
> >> I think that optimizing for this condition makes sense - most pushes (I
> >> would think) are pushes of objects we create locally, and thus no
> >> objects are missing.
> 
> Another simple thing I missed.  Why do we specifically refer to
> "push" here?  Is this codepath in pack-objects not used or less
> often used by upload-pack (which is what serves "fetch")?  
> 
> I just wanted to make sure that we are not optimizing for "push",
> trading efficiency for "fetch" off.

Ah...that's true. For "fetch" I think it's less important because the multiple roundtrips of the pack negotiation means that the packfiles are usually more specific, but this optimization will help "fetch" too. I don't think we're optimizing at the expense of "fetch" - any improvements should benefit both similarly.