From: Jeff Hostetler <git@jeffhostetler.com>
To: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Cc: Junio C Hamano <gitster@pobox.com>,
git@vger.kernel.org, Jeff Hostetler <jeffhost@microsoft.com>,
Jeff Hostetler via GitGitGadget <gitgitgadget@gmail.com>
Subject: Re: [RFC PATCH] trace2 API: don't save a copy of constant "thread_name"
Date: Wed, 12 Oct 2022 09:31:09 -0400 [thread overview]
Message-ID: <e138b178-99d9-e537-2cb1-c240962a35f2@jeffhostetler.com> (raw)
In-Reply-To: <221011.86h70ao4g6.gmgdl@evledraar.gmail.com>
On 10/11/22 9:31 AM, Ævar Arnfjörð Bjarmason wrote:
>
> On Mon, Oct 10 2022, Jeff Hostetler wrote:
>
>> On 10/7/22 6:03 AM, Ævar Arnfjörð Bjarmason wrote:
>>> On Thu, Oct 06 2022, Junio C Hamano wrote:
>>>
>>>> Ævar Arnfjörð Bjarmason <avarab@gmail.com> writes:
>>>>
>>>>> A cleaned up version of the test code I had on top of "master", RFC
>>>>> because I may still be missing some context here. E.g. maybe there's a
>>>>> plan to dynamically construct these thread names?
>>>>
[...]
> I left more extensive commentary in the side-thread in
> https://lore.kernel.org/git/221011.86lepmo5dn.gmgdl@evledraar.gmail.com/,
> just a quick reply here.
>
>> WRT optimizing memory usage. We're talking about ~25 byte buffer
>> per thread. Most commands execute in 1 thread -- if they read the
>> index they may have ~10 threads (depending on the size of the index
>> and if preload-index is enabled). So, I don't think we really need
>> to optimize this. Threading is used extensively in fsmonitor-daemon,
>> but it creates a fixed thread-pool at startup, so it may have ~12
>> threads. Again, not worth optimizing for the thread-name field.
>
> Yes, I agree it's not worth optimizing.
>
> The reason for commenting on this part is that it isn't clear to me why
> your proposed patch then isn't doing the more obvious "it's not worth
> optimizing" pattern, per Junio's [1] comment on the initial version.
>
> The "flex array" method is seemingly taking pains to reduce the runtime
> memory use of these by embedding this string in the space reserved for
> the struct.
>
> So it's just meant as a question for you & the proposed patch.
I think we're converging on some common understanding (and I
think we've gone around on this topic more than enough). :-)
I really was just trying to get rid of the strbuf and make it
a fixed string -- I chose a flex-array rather than just detaching
the buffer from a local in the thread-start code. I should have
done the latter. I saw the flex-array as a fixed-size object
that can't be replaced or extended (without recreating the
thread-local storage) -- yes, people could overwrite existing
bytes in-place in the flex-array, but who does that??
I understood what you were asking (illustrated in your RFC).
That is, I understood the "what/how" you wanted to do to refactor /
redesign the field, but I couldn't understand the "why". That
is, why you've taken such interest in this field (and such
a relatively unimportant change). We've spent nearly a week
discussing it and we both agree that the optimization that I
didn't suggest isn't worth doing. (I'm paraphrasing slightly.) :-)
So, rather than continuing with the back-n-forth, let me skip
over the remaining questions in this thread and prepare a re-roll.
Hopefully, I can simplify and more clearly explain the method to
my madness and we can move on.
>> Now, if you want to optimize over all trace2 events (a completely
>> different topic), you could create a large scratch strbuf buffer in
>> each thread context and use it so that we don't have to malloc/free
>> during each trace message. That might be worth while.
>
> *nod*
I'll make a note to revisit this idea in a future series.
Thanks
Jeff
next prev parent reply other threads:[~2022-10-12 13:31 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-04 16:19 [PATCH 0/9] Trace2 timers and counters and some cleanup Jeff Hostetler via GitGitGadget
2022-10-04 16:19 ` [PATCH 1/9] builtin/merge-file: fix compiler warning on MacOS with clang 11.0.0 Jeff Hostetler via GitGitGadget
2022-10-04 16:20 ` [PATCH 2/9] builtin/unpack-objects.c: " Jeff Hostetler via GitGitGadget
2022-10-04 16:20 ` [PATCH 3/9] trace2: use size_t alloc,nr_open_regions in tr2tls_thread_ctx Jeff Hostetler via GitGitGadget
2022-10-04 16:20 ` [PATCH 4/9] tr2tls: clarify TLS terminology Jeff Hostetler via GitGitGadget
2022-10-04 16:20 ` [PATCH 5/9] trace2: rename trace2 thread_name argument as name_hint Jeff Hostetler via GitGitGadget
2022-10-04 16:20 ` [PATCH 6/9] trace2: convert ctx.thread_name to flex array Jeff Hostetler via GitGitGadget
2022-10-05 11:14 ` Ævar Arnfjörð Bjarmason
2022-10-06 16:28 ` Jeff Hostetler
2022-10-10 18:31 ` Jeff Hostetler
2022-10-05 18:03 ` Junio C Hamano
2022-10-06 21:05 ` Ævar Arnfjörð Bjarmason
2022-10-06 21:50 ` Junio C Hamano
2022-10-07 1:10 ` [RFC PATCH] trace2 API: don't save a copy of constant "thread_name" Ævar Arnfjörð Bjarmason
2022-10-07 1:16 ` Junio C Hamano
2022-10-07 10:03 ` Ævar Arnfjörð Bjarmason
2022-10-10 19:16 ` Jeff Hostetler
2022-10-11 13:31 ` Ævar Arnfjörð Bjarmason
2022-10-12 13:31 ` Jeff Hostetler [this message]
2022-10-10 19:05 ` Jeff Hostetler
2022-10-11 12:52 ` Ævar Arnfjörð Bjarmason
2022-10-11 14:40 ` Junio C Hamano
2022-10-10 18:39 ` [PATCH 6/9] trace2: convert ctx.thread_name to flex array Jeff Hostetler
2022-10-04 16:20 ` [PATCH 7/9] api-trace2.txt: elminate section describing the public trace2 API Jeff Hostetler via GitGitGadget
2022-10-04 16:20 ` [PATCH 8/9] trace2: add stopwatch timers Jeff Hostetler via GitGitGadget
2022-10-04 16:20 ` [PATCH 9/9] trace2: add global counter mechanism Jeff Hostetler via GitGitGadget
2022-10-05 13:04 ` [PATCH 0/9] Trace2 timers and counters and some cleanup Ævar Arnfjörð Bjarmason
2022-10-06 15:45 ` Jeff Hostetler
2022-10-06 18:12 ` Derrick Stolee
2022-10-12 18:52 ` [PATCH v2 0/7] " Jeff Hostetler via GitGitGadget
2022-10-12 18:52 ` [PATCH v2 1/7] trace2: use size_t alloc,nr_open_regions in tr2tls_thread_ctx Jeff Hostetler via GitGitGadget
2022-10-12 18:52 ` [PATCH v2 2/7] tr2tls: clarify TLS terminology Jeff Hostetler via GitGitGadget
2022-10-13 21:12 ` Junio C Hamano
2022-10-12 18:52 ` [PATCH v2 3/7] api-trace2.txt: elminate section describing the public trace2 API Jeff Hostetler via GitGitGadget
2022-10-12 18:52 ` [PATCH v2 4/7] trace2: rename the thread_name argument to trace2_thread_start Jeff Hostetler via GitGitGadget
2022-10-12 21:06 ` Ævar Arnfjörð Bjarmason
2022-10-20 14:40 ` Jeff Hostetler
2022-10-13 21:12 ` Junio C Hamano
2022-10-12 18:52 ` [PATCH v2 5/7] trace2: convert ctx.thread_name from strbuf to pointer Jeff Hostetler via GitGitGadget
2022-10-13 21:12 ` Junio C Hamano
2022-10-12 18:52 ` [PATCH v2 6/7] trace2: add stopwatch timers Jeff Hostetler via GitGitGadget
2022-10-13 21:12 ` Junio C Hamano
2022-10-20 14:42 ` Jeff Hostetler
2022-10-12 18:52 ` [PATCH v2 7/7] trace2: add global counter mechanism Jeff Hostetler via GitGitGadget
2022-10-20 18:28 ` [PATCH v3 0/8] Trace2 timers and counters and some cleanup Jeff Hostetler via GitGitGadget
2022-10-20 18:28 ` [PATCH v3 1/8] trace2: use size_t alloc,nr_open_regions in tr2tls_thread_ctx Jeff Hostetler via GitGitGadget
2022-10-20 18:28 ` [PATCH v3 2/8] tr2tls: clarify TLS terminology Jeff Hostetler via GitGitGadget
2022-10-20 18:28 ` [PATCH v3 3/8] api-trace2.txt: elminate section describing the public trace2 API Jeff Hostetler via GitGitGadget
2022-10-20 18:28 ` [PATCH v3 4/8] trace2: rename the thread_name argument to trace2_thread_start Jeff Hostetler via GitGitGadget
2022-10-20 18:28 ` [PATCH v3 5/8] trace2: improve thread-name documentation in the thread-context Jeff Hostetler via GitGitGadget
2022-10-20 18:57 ` Ævar Arnfjörð Bjarmason
2022-10-20 20:15 ` Jeff Hostetler
2022-10-20 18:28 ` [PATCH v3 6/8] trace2: convert ctx.thread_name from strbuf to pointer Jeff Hostetler via GitGitGadget
2022-10-20 18:28 ` [PATCH v3 7/8] trace2: add stopwatch timers Jeff Hostetler via GitGitGadget
2022-10-20 20:25 ` Junio C Hamano
2022-10-20 20:52 ` Jeff Hostetler
2022-10-20 20:55 ` Junio C Hamano
2022-10-21 21:51 ` Jeff Hostetler
2022-10-20 18:28 ` [PATCH v3 8/8] trace2: add global counter mechanism Jeff Hostetler via GitGitGadget
2022-10-24 13:40 ` [PATCH v4 0/8] Trace2 timers and counters and some cleanup Jeff Hostetler via GitGitGadget
2022-10-24 13:41 ` [PATCH v4 1/8] trace2: use size_t alloc,nr_open_regions in tr2tls_thread_ctx Jeff Hostetler via GitGitGadget
2022-10-24 20:31 ` Junio C Hamano
2022-10-25 12:35 ` Derrick Stolee
2022-10-25 15:40 ` Junio C Hamano
2022-10-24 13:41 ` [PATCH v4 2/8] tr2tls: clarify TLS terminology Jeff Hostetler via GitGitGadget
2022-10-24 13:41 ` [PATCH v4 3/8] api-trace2.txt: elminate section describing the public trace2 API Jeff Hostetler via GitGitGadget
2022-10-24 13:41 ` [PATCH v4 4/8] trace2: rename the thread_name argument to trace2_thread_start Jeff Hostetler via GitGitGadget
2022-10-24 13:41 ` [PATCH v4 5/8] trace2: improve thread-name documentation in the thread-context Jeff Hostetler via GitGitGadget
2022-10-24 13:41 ` [PATCH v4 6/8] trace2: convert ctx.thread_name from strbuf to pointer Jeff Hostetler via GitGitGadget
2022-10-24 13:41 ` [PATCH v4 7/8] trace2: add stopwatch timers Jeff Hostetler via GitGitGadget
2022-10-24 13:41 ` [PATCH v4 8/8] trace2: add global counter mechanism Jeff Hostetler via GitGitGadget
2022-10-25 12:27 ` [PATCH v4 0/8] Trace2 timers and counters and some cleanup Derrick Stolee
2022-10-25 15:36 ` Junio C Hamano
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