On Fri, 3 Aug 2018, Martin Hicks wrote: > > Hi, > > I've run into a huge performance gap between running a g_mass_storage > gadget with the backing file pointing to a raw partition (/dev/mmcblk1) > vs. creating a file on an ext4 filesystem and exporting that. > > With the partition I see write rates around 5MB/s, and with > /proc/sys/vm/block_dump > enabled I can see that all writes are 512-byte single-sector writes. > > Using a file within ext4fs, I get around 20MB and block_dump shows large IOs > (mostly 2048 sector). > > Is there any way to get raw-partition to better use caching and not write back > every sector individually?
g_mass_storage does no buffering internally; the benefit you get with ext4 comes from buffering within the filesystem. I have no idea how much or what kind of buffering the block-layer drivers do for raw partition accesses. You're better off asking the people responsible for the block layer about that. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
