From: Johannes Schindelin <Johannes.Schindelin@gmx.de>
To: Jeff King <peff@peff.net>
Cc: git@vger.kernel.org, Jeff Hostetler <jeffhost@microsoft.com>,
Junio C Hamano <gitster@pobox.com>
Subject: Re: [PATCH] mingw: use OpenSSL's SHA-1 routines
Date: Fri, 10 Feb 2017 16:49:02 +0100 (CET) [thread overview]
Message-ID: <alpine.DEB.2.20.1702101647340.3496@virtualbox> (raw)
In-Reply-To: <20170210050237.gajicliueuvk6s5d@sigill.intra.peff.net>
Hi Peff,
On Fri, 10 Feb 2017, Jeff King wrote:
> On Thu, Feb 09, 2017 at 11:27:49PM +0100, Johannes Schindelin wrote:
>
> > From: Jeff Hostetler <jeffhost@microsoft.com>
> >
> > Use OpenSSL's SHA-1 routines rather than builtin block-sha1 routines.
> > This improves performance on SHA1 operations on Intel processors.
> >
> > OpenSSL 1.0.2 has made considerable performance improvements and
> > support the Intel hardware acceleration features. See:
> > https://software.intel.com/en-us/articles/improving-openssl-performance
> > https://software.intel.com/en-us/articles/intel-sha-extensions
> >
> > To test this I added/staged a single file in a gigantic repository
> > having a 450MB index file. The code in read-cache.c verifies the
> > header SHA as it reads the index and computes a new header SHA as it
> > writes out the new index. Therefore, in this test the SHA code must
> > process 900MB of data. Testing was done on an Intel I7-4770 CPU @
> > 3.40GHz (Intel64, Family 6, Model 60) CPU.
>
> I think this is only half the story. A heavy-sha1 workload is faster,
> which is good. But one of the original reasons to prefer blk-sha1 (at
> least on Linux) is that resolving libcrypto.so symbols takes a
> non-trivial amount of time. I just timed it again, and it seems to be
> consistently 1ms slower to run "git rev-parse --git-dir" on my machine
> (from the top-level of a repo).
>
> 1ms is mostly irrelevant, but it adds up on scripted workloads that
> start a lot of git processes.
You know my answer to that. If scripting slows things down, we should
avoid it in production code. As it is, scripting slows us down. Therefore
I work slowly but steadily to get rid of scripting where it hurts most.
Ciao,
Dscho
next prev parent reply other threads:[~2017-02-10 15:51 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-09 22:27 [PATCH] mingw: use OpenSSL's SHA-1 routines Johannes Schindelin
2017-02-09 23:41 ` Junio C Hamano
2017-02-11 8:01 ` Johannes Sixt
2017-02-11 18:51 ` Junio C Hamano
2017-02-13 17:16 ` Johannes Schindelin
2017-02-16 18:12 ` Johannes Sixt
2017-02-10 5:02 ` Jeff King
2017-02-10 15:49 ` Johannes Schindelin [this message]
2017-02-10 16:04 ` Jeff King
2017-02-13 17:46 ` Johannes Sixt
2017-02-13 19:42 ` Junio C Hamano
2017-02-13 21:07 ` Johannes Sixt
2017-02-13 22:38 ` Johannes Schindelin
2017-02-14 6:14 ` Johannes Sixt
2017-02-24 21:54 ` Junio C Hamano
2017-03-02 6:07 ` Johannes Sixt
2017-03-02 17:07 ` Junio C Hamano
2017-02-25 0:44 ` Linus Torvalds
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