On Tue, Apr 15, 2014 at 11:45 PM, Junio C Hamano <gitster@xxxxxxxxx> wrote:
> Ramsay Jones <ramsay@xxxxxxxxxxxxxxxxxxx> writes:
>
>> On 11/04/14 23:22, Junio C Hamano wrote:
>> [...]
>>> [New Topics]
>>>
>>> * nd/index-pack-one-fd-per-thread (2014-04-09) 1 commit
>>> - index-pack: work around thread-unsafe pread()
>>>
>>> Enable threaded index-pack on platforms without thread-unsafe
>>> pread() emulation.
>>>
>>> Will merge to 'next' and keep it there for the remainder of the cycle.
>>
>> The commit message for commit 512ebe5d ("index-pack: work around
>> thread-unsafe pread()", 25-03-2014) is a little misleading.
>
> OK. Can we have a concrete alternative?
>
> Multi-threaing of index-pack was disabled with c0f8654
> (index-pack: Disable threading on cygwin - 2012-06-26), because
> pread() implementations for Cygwin and MSYS were not thread
> safe. Recent Cygwin does offer usable pread() and we enabled
> multi-threading with 103d530f (Cygwin 1.7 has thread-safe pread,
> 2013-07-19).
>
> Work around this problem on platforms with a thread-unsafe
> pread() emulation by opening one file handle per thread; it
> would prevent parallel pread() on different file handles from
> stepping on each other.
>
> Also remove NO_THREAD_SAFE_PREAD that was introduced in c0f8654
> because it's no longer used anywhere.
>
> This workaround is unconditional, even for platforms with
> thread-safe pread() because the overhead is small (a couple file
> handles more) and not worth fragmenting the code.
>
OK to me.
--
Duy
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