>>>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 Still miss as buffer::ptr length diff with ::encode(crc, bl), right? So the previous ebl.crc32c(0) calculation would be also no need to cache. Regards Ning Yao 2015-11-11 18:05 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? > 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
