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From: Karel Zak <kzak@redhat.com>
To: Aurelien LAJOIE <orel@melix.net>
Cc: util-linux@vger.kernel.org
Subject: Re: [PATCH] libuuid: improve uuid_unparse() performance
Date: Wed, 25 Mar 2020 12:10:49 +0100
Message-ID: <20200325111049.jypz2csy2hqxoegr@ws.net.home> (raw)
In-Reply-To: <20200324212625.6934-1-orel@melix.net>

On Tue, Mar 24, 2020 at 10:26:25PM +0100, Aurelien LAJOIE wrote:
> There is 2 improvements:
> 
>  * remove useless uuid_unpack,
>  * directly print the hexa format from memory without using printf
>    we can do this as the bytes order is the network byte order

I'm not sure, but are you sure that whole UUID is in big-endian order? 
I think that last part (aka "node", 6 bytes) is not subject to swapping. 
It seems uuid_unpack() does nothing with the last part of the UUID.

But your patch works on LE as well as on BE, so I probably miss
something :-)

> before took 382623 us
> after  took  36740 us
> 
> Big Endian OpenBSD:
> before took 3138172 us
> after  took  180116 us

I guess all this is about sprintf(), another way would be to use
uuid_unpack() but avoid sprintf().

    Karel

-- 
 Karel Zak  <kzak@redhat.com>
 http://karelzak.blogspot.com


  reply index

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-24 21:26 Aurelien LAJOIE
2020-03-25 11:10 ` Karel Zak [this message]
2020-03-26  0:54   ` Aurélien Lajoie
2020-03-25 14:16 ` Peter Cordes
2020-03-26  1:06   ` Aurélien Lajoie
2020-03-26  2:13     ` Peter Cordes
2020-03-26 23:22       ` Peter Cordes

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