Think I got a handle on this: The updates in LinkedListTest specifically directly "trail" the inserts - i.e we insert rows, put the row keys onto a queue, and then the updater thread immediately updates the same rows which were just inserted.
This means that most of the updates should hit MRS, rather thane one of the DRS. Prior to my patch, we would check MRS for updates, and only if it missed there, go and consult DRS. Now, we do things in the opposite direction, and check all the MRS for the row before we try MRS (only if we didn't find it anywhere). This is probably a common enough use case (updating recently-inserted data) that it's worth preserving the optimized path. I'll work on how to keep that optimization without hurting code clarity too much. -Todd On Thu, Apr 6, 2017 at 10:46 AM, Todd Lipcon <[email protected]> wrote: > Seeing some issues with write ops timing out in linked_list-test: > http://dist-test.cloudera.org:8080/test_drilldown?test_name=linked_ > list-test > > It seems like the timeouts are from the updater thread, so it's possible > the patch regressed performance for UPDATEs -- the benchmarking focused on > INSERT workload. > > I'll investigate this today and if it seems like there's a big regression, > will either fix or revert. > > -Todd > > > On Wed, Apr 5, 2017 at 10:21 PM, Todd Lipcon <[email protected]> wrote: > >> Hey all, >> >> I just pushed a patch which restructures the write path for batched >> operations in a moderately serious way[1]. It's been through several rounds >> of review and a good amount of stress testing, but I wouldn't be super >> surprised if there were some bug which created a flaky test. >> >> I'll be watching out on the flaky dashboard the next couple days, but if >> you see any funky looking test failures please ping me to take a look. If >> anything appears to regress, we can revert and re-land after debugging. >> >> -Todd >> >> [1] https://github.com/apache/kudu/commit/4568f2a4cbd999d5a2 >> ab64d285205b8d30997339 >> >> -- >> Todd Lipcon >> Software Engineer, Cloudera >> > > > > -- > Todd Lipcon > Software Engineer, Cloudera > -- Todd Lipcon Software Engineer, Cloudera
