OK, thank you very much. 2018-01-31 15:55 GMT+08:00 Michael Lyle <mlyle@xxxxxxxx>: > Hi Pony Cheng-- > > On 01/28/2018 11:23 PM, Pony Cheng wrote: >> Hi all: >> I'm reading the source code of bcache, and I'm so confused about >> journal. Journal just use bucket of cache, why we need it, and what's >> the real purpose of journal in bcache. If we write to the bucket, do >> we need write it to journal first? > > The purpose of the journal is to control write amplification from btree > node writes. If we have 100 things to insert into the btree because > we're just caching new things, and this would touch 100 different btree > nodes, we can just write the new nodes to the journal in a single I/O > instead of doing 100 different updates. Later, we can free the journal > pages by doing those updates, but hopefully be doing more than one > update to each btree node and significantly lessen the total amount of I/O. > >> >> How do you think of these? >> >> Pony Cheng > > Regards, > > Mike -- To unsubscribe from this list: send the line "unsubscribe linux-bcache" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
