>>the code logic would touch crc cache is bufferlist::crc32c and invalidate_crc. >Also for pg_log::_write_log(), but seems it is always miss and use at >once, no need to cache crc actually? Oh, no, it will be hit in FileJournal writing Regards Ning Yao 2015-11-11 18:03 GMT+08:00 Ning Yao <zay11022@xxxxxxxxx>: >>>the code logic would touch crc cache is bufferlist::crc32c and invalidate_crc. > Also for pg_log::_write_log(), but seems it is always miss and use at > once, no need to cache crc actually? > > So we may need to add some option to enable or disable it, or some > identifier to instruct bufferlist wheher crc should be cached when > initiating a new bufferlist. I think it may still be useful on the > platform without hardware crc acceleration or large chunks writing (as > it may relate to the length of buffer::ptr). So we can bypass the > small buffer::ptr without crc cache Or also don't cache the things > like pg_info, attrs as they are always not reused in FileJournal > writing? > Regards > Ning Yao > > > 2015-11-11 16:25 GMT+08:00 Evgeniy Firsov <Evgeniy.Firsov@xxxxxxxxxxx>: >> Rb-tree construction, insertion, which needs memory allocation, mutex >> lock, unlock is more CPU expensive then streamlined crc calculation of >> sometimes 100 bytes or less. >> >> On 11/11/15, 12:03 AM, "池信泽" <xmdxcxz@xxxxxxxxx> wrote: >> >>>Ah, I confuse that why the crc cache logic would exhaust so much cpu. >>> >>>2015-11-11 15:27 GMT+08:00 Evgeniy Firsov <Evgeniy.Firsov@xxxxxxxxxxx>: >>>> Hello, Guys! >>>> >>>> While running CPU bound 4k block workload, I found that disabling crc >>>> cache in the buffer::raw gives around 7% performance improvement. >>>> >>>> If there is no strong use case which benefit from that cache, we would >>>> remove it entirely, otherwise conditionally enable it based on the >>>>object >>>> size. >>>> >>>> ‹ >>>> Evgeniy >>>> >>>> -- >>>> 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 >>> >>> >>> >>>-- >>>Regards, >>>xinze >> -- 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
