On Fri, May 17, 2013 at 06:51:23PM +0200, frankcmoeller@xxxxxxxx wrote: > - Why do you throw away buffer cache and don't store it on disk during umount? The initialization of the buffer cache is quite awful for application which need a specific write throughput. > - A workaround would be to read whole /proc/.../mb_groups file right after every mount. Correct? Simply adding "cat /proc/fs/<dev>/mb_groups > /dev/null" to one of the /etc/init.d scripts, or to /etc/rc.local is probably the simplest fix, yes. > - I can try to add a mount option to initialize the cache at mount time. Would you be interested in such a patch? Given the simple nature of the above workaround, it's not obvious to me that trying to make file system format changes, or even adding a new mount option, is really worth it. This is especially true given that mount -a is sequential so if there are a large number of big file systems, using this as a mount option would be slow down the boot significantly. It would be better to do this parallel, which you could do in userspace much more easily using the "cat /proc/fs/<dev>/mb_groups" workaround. > - I can see (see debug output) that the call of ext4_wait_block_bitmap in mballoc.c line 848 takes during buffer cache initialization the longest time (some 1/100 of a second). Can this be improved? The delay is caused purely by I/O delay, so short of replacing the HDD with a SSD, not really.... Regards, - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
