From: Johannes Thumshirn <jthumshirn@suse.de>
To: "Holger Hoffstätte" <holger@applied-asynchrony.com>
Cc: Linux BTRFS Mailinglist <linux-btrfs@vger.kernel.org>
Subject: Re: [PATCH v2 0/4] Support xxhash64 checksums
Date: Thu, 22 Aug 2019 14:54:18 +0200 [thread overview]
Message-ID: <20190822125418.GF4052@x250> (raw)
In-Reply-To: <ed9e2eaa-7637-9752-94bb-fd415ab2b798@applied-asynchrony.com>
On Thu, Aug 22, 2019 at 02:28:53PM +0200, Holger Hoffstätte wrote:
> On 8/22/19 1:40 PM, Johannes Thumshirn wrote:
> > Now that Nikolay's XXHASH64 support for the Crypto API has landed and BTRFS is
> > prepared for an easy addition of new checksums, this patchset implements
> > XXHASH64 as a second, fast but not cryptographically secure checksum hash.
>
> Question from the cheap seats.. :)
>
> I know that crc32c-intel uses native SSE 4.2 instructions, but so far I have
> been unable to find benchmarks or explanations why adding xxhash64 benefits
> btrfs. All benchmarks seem to be against crc32c in *software*, not the
> SSE4.2-enabled version (or I can't read). I mean, it's great that xxhash64 is
> really fast for a software implementation, but how does btrfs benefit from this
> compared to using crc32-intel?
>
> Verifying that plugging in other hash impls works (e.g. as preparation for
> stronger impls) has value, but it's probably not something most
> users care about.
>
> Maybe there are obscure downsides to crc32c-intel like instruction latency
> (def. a problem for AVX512), cache pollution..?
>
> Just curious.
It's not so much about the performance aspect of xxhash64 vs crc32c. xxhash64
has a lower collission proability compared to crc32c, which for instance makes
it a good candidate to use for de-duplication.
HTH,
Johannes
--
Johannes Thumshirn SUSE Labs Filesystems
jthumshirn@suse.de +49 911 74053 689
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Felix Imendörffer, Mary Higgins, Sri Rasiah
HRB 21284 (AG Nürnberg)
Key fingerprint = EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850
next prev parent reply other threads:[~2019-08-22 12:54 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-22 11:40 [PATCH v2 0/4] Support xxhash64 checksums Johannes Thumshirn
2019-08-22 11:40 ` [PATCH v2 1/4] btrfs: turn checksum type define into a enum Johannes Thumshirn
2019-08-22 11:40 ` [PATCH v2 2/4] btrfs: create structure to encode checksum type and length Johannes Thumshirn
2019-08-22 12:11 ` Johannes Thumshirn
2019-08-22 13:22 ` [PATCH v2.1] " Johannes Thumshirn
2019-08-22 11:40 ` [PATCH v2 3/4] btrfs: use xxhash64 for checksumming Johannes Thumshirn
2019-08-22 11:40 ` [PATCH v2 4/4] btrfs: sysfs: export supported checksums Johannes Thumshirn
2019-08-22 12:28 ` [PATCH v2 0/4] Support xxhash64 checksums Holger Hoffstätte
2019-08-22 12:54 ` Johannes Thumshirn [this message]
2019-08-22 15:40 ` Peter Becker
2019-08-23 9:38 ` Paul Jones
2019-08-23 9:43 ` Paul Jones
2019-08-23 17:08 ` Adam Borowski
2019-08-26 12:27 ` Austin S. Hemmelgarn
2019-08-27 0:33 ` Adam Borowski
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190822125418.GF4052@x250 \
--to=jthumshirn@suse.de \
--cc=holger@applied-asynchrony.com \
--cc=linux-btrfs@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.