[openstack-dev] Concerns about Gnocchi's performance

2015-01-15 Thread 张灿
Hello, I’m testing gnocchi to work with ceilometer these days and I have some concerns about its performance. I noticed in the code, every time a measure gets updated, gnocchi first reads all the previous contents of that measure, updates the measure in memory and writes the updated contents

Re: [openstack-dev] Concerns about Gnocchi's performance

2015-01-15 Thread Julien Danjou
On Thu, Jan 15 2015, 张灿 wrote: Hi, I noticed in the code, every time a measure gets updated, gnocchi first reads all the previous contents of that measure, updates the measure in memory and writes the updated contents as well as original contents back. IMHO, the overhead here could be very

Re: [openstack-dev] Concerns about Gnocchi's performance

2015-01-15 Thread 张灿
On Jan 15, 2015, at 18:46, Julien Danjou jul...@danjou.info wrote: Yep, that's the main downside of the use of the Carbonara based backend in Gnocchi. But honestly, since it's download/upload are parallel and the file size is quite small, sending a metric should be pretty fast in most

Re: [openstack-dev] Concerns about Gnocchi's performance

2015-01-15 Thread Julien Danjou
On Thu, Jan 15 2015, 张灿 wrote: As a further question, how do you estimate the storage impact of a vm instance’s metrics? I’m not very sure about the `back_window` and `definition` part, could you clarify that for me? That defines the number of measure (data points) that are stored for each