On Fri, 27 Nov 2015 10:21:31 +0800 Qu Wenruo <quwenruo@xxxxxxxxxxxxxx> 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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