On 03/15/2015 08:42 PM, Mike Christie wrote: > On 03/15/2015 07:54 PM, Mike Christie wrote: >> On 03/09/2015 11:15 AM, Nick Fisk wrote: >>> Hi Mike, >>> >>> I was using bs_aio with the krbd and still saw a small caching effect. I'm >>> not sure if it was on the ESXi or tgt/krbd page cache side, but I was >>> definitely seeing the IO's being coalesced into larger ones on the krbd >> >> I am not sure what you mean here. By coalescing you mean merging right? >> That is not the same as caching. Coalescing/merging is expected for both >> aio and rdwr. > > For being able to see caching with aio though, I think you are right and > there might be a case where can use buffered writes even when using > O_DIRECT to the rbd device. I am not too familiar with that code, so let > me ping a person that works here and get back to the list. I talked to the AIO person here and confirmed that the code can drop down to buffered writes. However, if that happens it will then make it still look like O_DIRECT by making sure writes are written back and pages are invalidated. If you want I can send you a patch to also do O_SYNC when doing AIO, so we can make sure flushes/barriers are also done. Send me the iometer workload when you get a chance, so I can test it out here. _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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