Can you try disabling congested_threshold? That's the one other option that allows data to bypass the cache. On Thu, Mar 14, 2013 at 7:32 AM, CoRpO <corpo@xxxxxxxx> wrote: > Le 2013-03-14 13:17, CoRpO a écrit : > > >> Hi, >> >> I'm currently running the latest bcache (non-dev) on an ubuntu 12.04, >> and it seems to me that bcache doesn't cache anything >> >> The setup is as follow: >> >> - One drive for the system >> - a 480 GB SSD caching device (/dev/sdb) >> - a 10 drives Raid 5 (on a HP P410 controller) backing device >> (/dev/sdc) >> - 36 GB ram >> >> /dev/bcache0 mounted as /home >> >> The server is a file server, with lots of file but few of them served >> frequently. So that's why I've put bcache on it, to have frequently >> asked files on the caching device (which are bigger than the server's >> ram) >> >> I've filled the server with 16 TB of datas, and I see little to no >> usage of /dev/sdb >> >> # iostat -x 30 >> avg-cpu: %user %nice %system %iowait %steal %idle >> 0.05 0.00 0.74 10.92 0.00 88.30 >> >> Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s >> avgrq-sz avgqu-sz await r_await w_await svctm %util >> sda 0.00 0.40 0.00 0.83 0.00 5.07 >> 12.16 0.00 0.00 0.00 0.00 0.00 0.00 >> sdb 0.27 0.03 1.10 0.17 136.57 0.37 >> 216.21 0.00 0.95 1.09 0.00 0.53 0.07 >> sdc 0.00 0.00 185.53 0.03 23750.93 0.03 >> 255.98 3.14 16.90 16.90 0.00 4.40 81.59 >> bcache0 0.00 0.00 186.67 0.10 23896.00 0.32 >> 255.89 0.00 16.81 16.82 0.00 0.00 0.00 >> >> sequential_cutoff and sequential_merge are echoed 0 to disable them, >> because I want sequential IOs to be cached >> >> I get strange numbers from the variables. Some seems to indicate that >> bcache is doing its work, others seems not. >> I'm totally puzzled. Am I doing something wrong ? It bcache suited for >> what I want to do ? Is it a bug ? >> >> I've even tried to recreate the caching device to get rid of the data >> that was on it during data was put on the backing device. >> As noted in this mailing-list, I made some writes to the device to >> allow the btree to split/grow if needed, and seen no changes. >> >> Here are the details : >> >> # cat /sys/block/bcache0/bcache/cache/internal/active_journal_entries >> 3 >> >> # cat /sys/block/bcache0/bcache/cache/internal/bset_tree_stats >> btree nodes: 1 >> written sets: 2 >> unwritten sets: 1 >> written key bytes: 156768 >> unwritten key bytes: 96 >> floats: 1222 >> failed: 63 >> >> # cat /sys/block/bcache0/bcache/cache/internal/btree_nodes >> 1 >> # cat /sys/block/bcache0/bcache/cache/internal/btree_used_percent >> 46 >> # cat /sys/block/bcache0/bcache/cache/average_key_size >> 384k >> # cat /sys/block/bcache0/bcache/cache/btree_cache_size >> 0 >> # cat /sys/block/bcache0/bcache/cache/cache_available_percent >> 99 >> # cat /sys/block/bcache0/bcache/cache/root_usage_percent >> 47 >> # cat /sys/block/bcache0/bcache/cache/tree_depth >> 0 >> # cat /sys/block/bcache0/bcache/cache_mode >> writethrough [writeback] writearound none >> # cat /sys/block/bcache0/bcache/readahead >> 1.0M >> # cat /sys/block/bcache0/bcache/stats_hour/bypassed >> 0 >> # cat /sys/block/bcache0/bcache/stats_hour/cache_hit_ratio >> 100 >> # cat /sys/block/bcache0/bcache/stats_hour/cache_hits >> 960779 >> # cat /sys/block/bcache0/bcache/stats_hour/cache_misses >> 0 >> # cat /sys/block/bcache0/bcache/stats_hour/cache_readaheads >> 0 >> # cat /sys/block/bcache0/bcache/cache/cache0/freelist_percent >> 0 >> # cat /sys/block/bcache0/bcache/cache/cache0/priority_stats >> Unused: 89% >> Metadata: 0% >> Average: 4141 >> Sectors per Q: 3109760 >> Quantiles: [4162 4189 4193 4197 4201 4205 4209 4213 4217 4221 4225 >> 4229 4233 4237 4241 4245 4249 4253 4257 4260 4264 4268 4272 4276 4280 >> 4284 4288 4292 4296 4300 4304] >> # cat /sys/block/bcache0/bcache/cache/cache0/written >> 47.4G >> # cat /sys/block/bcache0/bcache/cache/cache0/cache_replacement_policy >> [lru] fifo random >> # cat /sys/block/bcache0/bcache/cache/cache0/nbuckets >> 915661 >> # cat /sys/block/bcache0/bcache/cache/cache0/metadata_written >> 13.3M >> >> I don't know what to try. At first I used bcache-3.2, and seeing this >> beavior made me switch to bcache and 3.8 kernel. Tried bcache-dev, too, >> but the server doesn't boot, kernel stuck in a softlock @[bcache:345] >> (no idea of the meaning) >> >> What am I doing wrong ? >> There's little to no activity on the caching device, I though there >> would be write operations to cache served files, but the only writes are >> when I put new files. The pattern is 99% read of big files (~ from 100 >> MB to 10 GB) >> >> Thank you > > > In addition, here are the results of a 1 minutes blktrace > > Total (sdb): > Reads Queued: 3, 10KiB Writes Queued: 8, > 2KiB > Read Dispatches: 3, 10KiB Write Dispatches: 8, > 2KiB > Reads Requeued: 0 Writes Requeued: 0 > Reads Completed: 3, 10KiB Writes Completed: 8, > 2KiB > Read Merges: 0, 0KiB Write Merges: 0, > 0KiB > IO unplugs: 3 Timer unplugs: 0 > > Total (sdc): > Reads Queued: 14674, 1878MiB Writes Queued: 3, > 10KiB > Read Dispatches: 14674, 1878MiB Write Dispatches: 3, > 10KiB > Reads Requeued: 0 Writes Requeued: 0 > Reads Completed: 14678, 1879MiB Writes Completed: 3, > 10KiB > Read Merges: 0, 0KiB Write Merges: 0, > 0KiB > IO unplugs: 14674 Timer unplugs: 0 > > Total (bcache0): > Reads Queued: 14674, 1878MiB Writes Queued: 3, > 2KiB > Read Dispatches: 0, 0KiB Write Dispatches: 0, > 0KiB > Reads Requeued: 0 Writes Requeued: 0 > Reads Completed: 0, 0KiB Writes Completed: 0, > 0KiB > Read Merges: 0, 0KiB Write Merges: 0, > 0KiB > IO unplugs: 0 Timer unplugs: 0 > > > -- > 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 -- 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
