On Mon, Oct 23, 2017 at 4:25 PM, 陶冬冬 <tdd21151186@xxxxxxxxx> wrote: > > Thanks Zheng, so, do you mean client B can have “Fs" cap and thle same time client A can have “Fw” for the same file ? > so that, client A and client B can write and read the same file at same time (different object) ? > Reading within file size only requires "Fr" cap. If read reaches file size and there is no "Fs", checking EOF requires an extra getattr request. > also another extended question, does that mean client A and client B can both have the “Fw” for the same file same time, and also they can write the same file at same time (different object) ? > > Dongdong > > > >> 在 2017年10月23日，下午3:55，Yan, Zheng <ukernel@xxxxxxxxx> 写道： >> >> On Mon, Oct 23, 2017 at 12:50 PM, 陶冬冬 <tdd21151186@xxxxxxxxx> wrote: >>> Dear Cephers, >>> >>> I have one issue about cephfs, suppose we got below scenario: >>> client A write one file with interval1 (offset1, length1) >>> then client B read the same file with interval2 (offset2, length2). >>> but due to capability system controlled by mds, client B have to wait until client A finish its write operation (including flushing its buffer to osd) >> >> Client B only need to wait until Client A finishes flush buffer to >> osd. If Client B keeps the file descriptor open, writing to page cache >> gets disabled on client A, reading from client B does not need to wait >> for writing on client A (different object). >> >>> Even if interval1 and interval2 belongs to two different object of that file, client B still have to wait client A. >>> >>> I’m wondering why mds doesn’t try to control the caps based on object rather than whole file? >> >> because mds can't foresee which offset client want to read/write. the >> overhead for issuing caps for each read/write syscall is too high. >> >>> >>> Thanks, >>> Dongdong > -- 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
