>>>>> Eric Sandeen (ES) writes: ES> Alex Tomas wrote: >> 3) scalable reservation >> required for delayed allocation to avoid -ENOSPC at flush time. >> current version uses per-sb spinlock. ES> Can you elaborate on this issue? Shouldn't delayed allocation ES> decrement free space immediately, and only the actual block location ES> choice is delayed? Or is this due to potential extra metadata space ES> required as blocks are allocated? exactly. in this case, reservation has nothing to do with allocation or preallocation of real blocks. this is just a *per-sb counter* of blocks reserved for allocation at flush time. it includes all non-allocated-yet blocks and metadata needed to allocate them (bitmaps, group descriptors, blocks extent tree, etc). the previous version of mballoc has reservation, but it doesn't scale very well being a single global counter protected by the spinlock. at least, in many regular loads I observed the reservation function in top30 of oprofile. thanks, Alex - 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
