On Fri, May 1, 2015 at 7:54 AM, Steve Capper <steve.capper@xxxxxxxxxx> wrote: > Hello, > Whilst testing Ceph 0.94.1 on 64-bit ARM hardware, I noticed that > switching the kernel PAGE_SIZE from 4KB to 64KB caused an increase by > a factor of ~6 in the total amount of data written to disk (according > to blktrace) by the OSD when running the RBD bench-write test (with > --io-pattern rand, --io-size=4096, --num-threads=16, --io-total=$((50 > << 20))). > > Delving into the source, it is apparent that the FileJournal code uses > the current page size for the block size. I was wondering why > something like the block device sector size wasn't used instead? Is > there a mmap somewhere that I missed, or are fewer larger blocks > better for most use cases? (The use case above may be overly > contrived?). This isn't an area of the kernel I know much about, but doesn't the page cache work in memory page size, regardless of what the disk is doing? FileJournal/FileStore are definitely trying to be friendly to what the page cache is up to. -Greg -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
