From: Junio C Hamano <gitster@pobox.com>
To: Jeff King <peff@peff.net>
Cc: William Duclot <william.duclot@ensimag.grenoble-inp.fr>,
git@vger.kernel.org, antoine.queru@ensimag.grenoble-inp.fr,
francois.beutin@ensimag.grenoble-inp.fr, mhagger@alum.mit.edu,
Johannes.Schindelin@gmx.de, mh@glandium.org
Subject: Re: [PATCH V2 3/3] strbuf: allow to use preallocated memory
Date: Mon, 06 Jun 2016 16:25:55 -0700 [thread overview]
Message-ID: <xmqq7fe1vr0c.fsf@gitster.mtv.corp.google.com> (raw)
In-Reply-To: <xmqqbn3dvr22.fsf@gitster.mtv.corp.google.com> (Junio C. Hamano's message of "Mon, 06 Jun 2016 16:24:53 -0700")
Junio C Hamano <gitster@pobox.com> writes:
> Jeff King <peff@peff.net> writes:
>
>>> I think that call should reset line.buf to the original buffer on
>>> the stack, instead of saying "Ok, I'll ignore the original memory
>>> not owned by us and instead keep pointing at the allocated memory",
>>> as the allocation was done as a fallback measure.
>>
>> I am not sure I agree. Do we think accessing the stack buffer is somehow
>> cheaper than the heap buffer (perhaps because of cache effects)? If so,
>> how much cheaper?
>
> This is not about stack vs heap or even "cheaper" (whatever your
> definition of cheap is). The principle applies equally if the
> original buffer came from BSS.
>
> Perhaps I made it clearer by using a more exaggerated example e.g. a
s/I made/I should have made/; sorry but I have a horrible wifi
around here today...
> typical expected buffer size of 128 bytes, but the third line of
> 1000 line input file was an anomaly that is 200k bytes long. I do
> not want to keep that 200k bytes after finishing to process that
> third line while using its initial 80 bytes for the remaining 977
> lines.
>
> By the way, William seemed to be unhappy with die(), but I actually
> think having a die() in the API may not be a bad thing if the check
> were about something more sensible. For example, even if a strbuf
> that can grow dynamically, capping the maximum size and say "Hey
> this is a one-lne-at-a-time text interface; if we need to grow the
> buffer to 10MB, there is something wrong and a producer of such an
> input does not even deserve a nice error message" could be an
> entirely sensible attitude. But that does not mean an initial
> allocation should be 10MB. If the expected typical workload fits
> within a lot lower bound, starting from there and allowing it to
> grow up to that maximum would be the more natural thing to do.
>
> And the problem I have with the proposed "fixed" is that it does not
> allow us to do that.
next prev parent reply other threads:[~2016-06-06 23:26 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-06 15:13 [PATCH V2 0/3] strbuf: improve API William Duclot
2016-06-06 15:13 ` [PATCH V2 1/3] strbuf: add tests William Duclot
2016-06-06 16:11 ` Matthieu Moy
2016-06-07 8:44 ` Johannes Schindelin
2016-06-06 15:13 ` [PATCH V2 2/3] pretty.c: rename strbuf_wrap() function William Duclot
2016-06-06 16:12 ` Matthieu Moy
2016-06-07 9:04 ` Johannes Schindelin
2016-06-06 15:13 ` [PATCH V2 3/3] strbuf: allow to use preallocated memory William Duclot
2016-06-06 16:17 ` Matthieu Moy
2016-06-06 17:19 ` Junio C Hamano
2016-06-06 20:39 ` William Duclot
2016-06-06 22:44 ` Junio C Hamano
2016-06-06 22:58 ` Jeff King
2016-06-06 23:24 ` Junio C Hamano
2016-06-06 23:25 ` Junio C Hamano [this message]
2016-06-06 23:30 ` Jeff King
2016-06-07 9:06 ` William Duclot
2016-06-07 18:10 ` Junio C Hamano
2016-06-08 16:20 ` Michael Haggerty
2016-06-08 18:07 ` Junio C Hamano
2016-06-08 19:19 ` Jeff King
2016-06-08 19:42 ` [PATCH] send-pack: use buffered I/O to talk to pack-objects Jeff King
2016-06-09 12:10 ` Matthieu Moy
2016-06-09 14:34 ` Ramsay Jones
2016-06-09 17:12 ` Jeff King
2016-06-09 22:40 ` Ramsay Jones
2016-06-09 16:40 ` Junio C Hamano
2016-06-09 17:14 ` Jeff King
2016-06-09 17:22 ` Matthieu Moy
2016-06-08 19:48 ` [PATCH V2 3/3] strbuf: allow to use preallocated memory Junio C Hamano
2016-06-08 19:52 ` Jeff King
2016-06-08 23:05 ` Junio C Hamano
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