From: Tang Junhui <[email protected]> LGTM, and I tested it, it promotes the write-back performance.
Reviewed-by: Tang Junhui <[email protected]> Tested-by: Tang Junhui <[email protected]> > From: Tang Junhui <[email protected]> > > In such scenario that there are some flash only volumes > , and some cached devices, when many tasks request these devices in > writeback mode, the write IOs may fall to the same bucket as bellow: > | cached data | flash data | cached data | cached data| flash data| > then after writeback of these cached devices, the bucket would > be like bellow bucket: > | free | flash data | free | free | flash data | > > So, there are many free space in this bucket, but since data of flash > only volumes still exists, so this bucket cannot be reclaimable, > which would cause waste of bucket space. > > In this patch, we segregate flash only volume write streams from > cached devices, so data from flash only volumes and cached devices > can store in different buckets. > > Compare to v1 patch, this patch do not add a additionally open bucket > list, and it is try best to segregate flash only volume write streams > from cached devices, sectors of flash only volumes may still be mixed > with dirty sectors of cached device, but the number is very small. > > Signed-off-by: Tang Junhui <[email protected]> > --- > drivers/md/bcache/alloc.c | 19 ++++++++++++++----- > 1 file changed, 14 insertions(+), 5 deletions(-) > mode change 100644 => 100755 drivers/md/bcache/alloc.c > > diff --git a/drivers/md/bcache/alloc.c b/drivers/md/bcache/alloc.c > old mode 100644 > new mode 100755 > index 0803563..4302922 > --- a/drivers/md/bcache/alloc.c > +++ b/drivers/md/bcache/alloc.c > @@ -514,15 +514,21 @@ struct open_bucket { > > /* > * We keep multiple buckets open for writes, and try to segregate different > - * write streams for better cache utilization: first we look for a bucket > where > - * the last write to it was sequential with the current write, and failing > that > - * we look for a bucket that was last used by the same task. > + * write streams for better cache utilization: first we try to segregate > flash > + * only volume write streams from cached devices, secondly we look for a > bucket > + * where the last write to it was sequential with the current write, and > + * failing that we look for a bucket that was last used by the same task. > * > * The ideas is if you've got multiple tasks pulling data into the cache at > the > * same time, you'll get better cache utilization if you try to segregate > their > * data and preserve locality. > * > - * For example, say you've starting Firefox at the same time you're copying a > + * For example, dirty sectors of flash only volume is not reclaimable, if > their > + * dirty sectors mixed with dirty sectors of cached device, such buckets > will > + * be marked as dirty and won't be reclaimed, though the dirty data of > cached > + * device have been written back to backend device. > + * > + * And say you've starting Firefox at the same time you're copying a > * bunch of files. Firefox will likely end up being fairly hot and stay in > the > * cache awhile, but the data you copied might not be; if you wrote all that > * data to the same buckets it'd get invalidated at the same time. > @@ -539,7 +545,10 @@ static struct open_bucket *pick_data_bucket(struct > cache_set *c, > struct open_bucket *ret, *ret_task = NULL; > > list_for_each_entry_reverse(ret, &c->data_buckets, list) > - if (!bkey_cmp(&ret->key, search)) > + if (UUID_FLASH_ONLY(&c->uuids[KEY_INODE(&ret->key)]) != > + UUID_FLASH_ONLY(&c->uuids[KEY_INODE(search)])) > + continue; > + else if (!bkey_cmp(&ret->key, search)) > goto found; > else if (ret->last_write_point == write_point) > ret_task = ret; > -- > 1.8.3.1 Thanks, Tang
