From: "René Scharfe" <l.s.r@web.de>
To: Jeff King <peff@peff.net>
Cc: Git List <git@vger.kernel.org>, Junio C Hamano <gitster@pobox.com>
Subject: Re: [PATCH 3/3] packfile: use oidset for bad objects
Date: Sat, 11 Sep 2021 19:16:51 +0200 [thread overview]
Message-ID: <480dba11-e321-68f8-3983-1d918c24fbbc@web.de> (raw)
In-Reply-To: <YTzhVfmObOf7DHqm@coredump.intra.peff.net>
Am 11.09.21 um 19:03 schrieb Jeff King:
> On Sat, Sep 11, 2021 at 06:08:38PM +0200, René Scharfe wrote:
>
>>>> + nth_midxed_object_oid(&oid, m, pos);
>>>> + if (oidset_contains(&p->bad_objects, &oid))
>>>> + return 0;
>>>
>>> Calling nth_midxed_object_oid() implies a memcpy() under the hood. In
>>> the old code, we'd skip that in the common case that we had no corrupt
>>> objects, but now we'll pay the cost regardless. memcpy() isn't _that_
>>> expensive, but I'd expect this to be a relatively hot code path.
>>>
>>> Is it worth sticking all of this inside:
>>>
>>> if (oidset_size(&p->bad_objects))
>>>
>>> ?
>>
>> Hard to say. It would certainly match the old code more closely. Is a
>> function call cheaper than copying 32 bytes? Depends on the CPU and
>> whether the hash is cached, I guess. And cached it probably is, because
>> the caller did a binary search for it..
>
> You already have a function call for nth_midxed_object_oid(), so
> checking oidset_size() would be a strict improvement.
If I read the assembly correctly nth_midxed_object_oid() is inlined by the
compiler in my build, as is nth_midxed_pack_entry(). Both are defined in
the same file, so other compilers may easily do the same.
>> We can pass on the original oid to avoid the nth_midxed_object_oid()
>> call, but inlining the whole thing might even be nicer.
>
> Yeah, it occurs to me that oidset_size() would be a good candidate for
> inlining, if that's what you mean.
True, but I meant something else (see patch 4/3). :)
René
next prev parent reply other threads:[~2021-09-11 17:17 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-11 7:50 [PATCH 0/3] packfile: use oidset for bad objects René Scharfe
2021-09-11 7:59 ` [PATCH 1/3] packfile: convert mark_bad_packed_object() to object_id René Scharfe
2021-09-11 8:00 ` [PATCH 2/3] packfile: convert has_packed_and_bad() " René Scharfe
2021-09-11 8:01 ` [PATCH 3/3] packfile: use oidset for bad objects René Scharfe
2021-09-11 14:26 ` Jeff King
2021-09-11 16:08 ` René Scharfe
2021-09-11 17:03 ` Jeff King
2021-09-11 17:16 ` René Scharfe [this message]
2021-09-11 14:27 ` [PATCH 0/3] " Jeff King
2021-09-11 16:08 ` [PATCH 4/3] midx: inline nth_midxed_pack_entry() René Scharfe
2021-09-11 17:03 ` René Scharfe
2021-09-11 17:07 ` Jeff King
2021-09-11 20:31 ` René Scharfe
2021-09-11 21:20 ` Jeff King
2021-09-11 23:39 ` René Scharfe
2021-09-11 20:31 ` [PATCH v2 0/5] packfile: use oidset for bad objects René Scharfe
2021-09-11 20:36 ` [PATCH 1/5] oidset: make oidset_size() an inline function René Scharfe
2021-09-11 20:39 ` [PATCH 2/5] midx: inline nth_midxed_pack_entry() René Scharfe
2021-09-11 20:40 ` [PATCH 3/5] packfile: convert mark_bad_packed_object() to object_id René Scharfe
2021-09-11 20:42 ` [PATCH v2 4/5] packfile: convert has_packed_and_bad() " René Scharfe
2021-09-11 20:43 ` [PATCH v2 5/5] packfile: use oidset for bad objects René Scharfe
2021-09-11 20:45 ` [PATCH v2 0/5] " René Scharfe
2021-09-11 21:22 ` Jeff King
2021-09-11 23:59 ` Derrick Stolee
2021-09-12 1:51 ` Taylor Blau
2021-09-12 2:29 ` Taylor Blau
2021-09-12 3:51 ` Derrick Stolee
2021-09-12 4:01 ` Taylor Blau
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