From: Roman Mamedov <rm@romanrm.net>
To: Qu Wenruo <quwenruo@cn.fujitsu.com>
Cc: Lukas Pirl <btrfs@lukas-pirl.de>, <linux-btrfs@vger.kernel.org>
Subject: Re: implications of mixed mode
Date: Fri, 27 Nov 2015 10:40:28 +0500 [thread overview]
Message-ID: <20151127104028.4eb793ba@natsu> (raw)
In-Reply-To: <5657BE2B.10209@cn.fujitsu.com>
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On Fri, 27 Nov 2015 10:21:31 +0800
Qu Wenruo <quwenruo@cn.fujitsu.com> wrote:
> And some extra pros and cons due to fixed(4K) small(compared to 16K
> default) nodesize:
>
> + A little higher performance
> node/leaf size is restricted to sectorsize, smaller node/leaf,
> smaller range to lock.
> In our SSD test, operations with high concurrency, the performance is
> overall 10% better than 16K nodesize.
> And in extreme metadata operation case, like high concurrency on
> sequence write into small files, it can be 8 times the performance of
> default 16K nodesize.
This is surprising to read, as I thought 16K is generally faster and that's
why the default value was changed to it from 4K.
https://oss.oracle.com/~mason/blocksizes/
https://git.kernel.org/cgit/linux/kernel/git/mason/btrfs-progs.git/commit/?id=c652e4efb8e2dd76ef1627d8cd649c6af5905902
Seems like the 16K size prevents fragmentation, but since your SSDs do not care
much about fragmentation, that's not adding a benefit for them.
--
With respect,
Roman
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next prev parent reply other threads:[~2015-11-27 5:40 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-26 23:54 implications of mixed mode Lukas Pirl
2015-11-27 2:21 ` Qu Wenruo
2015-11-27 5:40 ` Roman Mamedov [this message]
2015-11-27 3:11 ` Duncan
2015-11-27 10:30 ` Lukas Pirl
2015-11-28 6:08 ` Duncan
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