I think jianjian refer to this(https://github.com/ceph/ceph/blob/master/src/kv/RocksDBStore.cc#L285) On Thu, May 19, 2016 at 2:43 PM, Sage Weil <sage@xxxxxxxxxxxx> wrote: > On Wed, 18 May 2016, Jianjian Huo wrote: >> On Wed, May 18, 2016 at 10:19 AM, Sage Weil <sage@xxxxxxxxxxxx> wrote: >> > >> > Hi Rajath! >> > >> > Great to hear you're interested in working with us outside of GSoC! >> > >> > On Wed, 18 May 2016, Haomai Wang wrote: >> > > Hi Rajath, >> > > >> > > We are glad to see your passion, from my view, sage is planning to >> > > implement a userspace cache in bluestore itself. Like >> > > (https://github.com/ceph/ceph/commit/b9ac31afe5a162176f019baa25348014a77f6ab8#commitcomment-17488250). >> > > >> > > I guess the cache won't be a generic cache interface. Instead it will >> > > be bound to specified needed object. So sage may give a brief? >> > >> > Part of the reason why this project wasn't at the top of our list (we got >> > fewer slots than we had projects) was because the BlueStore code is in >> > flux and moving quite quickly. For the BlueStore side, we are building a >> > simple buffer cache that is tied to an Onode (in-memory per-object >> > metadata structure) and integrated tightly with the read and write IO >> > paths. This will eliminate our use of the block device buffer cache for >> > user/object data. >> > >> > The other half of the picture, though, is the BlueFS layer that is >> > consumed by rocksdb: it also needs caching in order for rocksdb to perform >> > at all. My hope is that the code we write for the use data can be re-used >> > here as well, but it is still evolving. >> >> When Bluestore moves away from kernel cache to its own buffer cache, RocksDB can use its own buffer cache as well. >> RocksDB has this size configurable block cache to cache uncompressed data blocks, it can serve as buffer cache, >> since Bluestore don't compress meta data in RocksDB. > > What options control this? I was having trouble finding it the last time > I looked. We should switch it now (and use unbuffered IO from BlueFS) if > we can. > > Thanks! > sage -- 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
