Re: tools/virtiofs: Multi threading seems to hurt performance

[Stefan Hajnoczi]

On Fri, Sep 18, 2020 at 05:34:36PM -0400, Vivek Goyal wrote:
> And here are the comparision results. To me it seems that by default
> we should switch to 1 thread (Till we can figure out how to make
> multi thread performance better even when single process is doing
> I/O in client).

Let's understand the reason before making changes.

Questions:
 * Is "1-thread" --thread-pool-size=1?
 * Was DAX enabled?
 * How does cache=none perform?
 * Does commenting out vu_queue_get_avail_bytes() + fuse_log("%s:
   Queue %d gave evalue: %zx available: in: %u out: %u\n") in
   fv_queue_thread help?
 * How do the kvm_stat vmexit counters compare?
 * How does host mpstat -P ALL compare?
 * How does host perf record -a compare?
 * Does the Rust virtiofsd show the same pattern (it doesn't use glib
   thread pools)?

Stefan

> NAME                    WORKLOAD                Bandwidth       IOPS          
>   
> cache-auto              seqread-psync           690(MiB/s)      172k          
>   
> cache-auto-1-thread     seqread-psync           729(MiB/s)      182k          
>   
> 
> cache-auto              seqread-psync-multi     2578(MiB/s)     644k          
>   
> cache-auto-1-thread     seqread-psync-multi     2597(MiB/s)     649k          
>   
> 
> cache-auto              seqread-mmap            660(MiB/s)      165k          
>   
> cache-auto-1-thread     seqread-mmap            672(MiB/s)      168k          
>   
> 
> cache-auto              seqread-mmap-multi      2499(MiB/s)     624k          
>   
> cache-auto-1-thread     seqread-mmap-multi      2618(MiB/s)     654k          
>   
> 
> cache-auto              seqread-libaio          286(MiB/s)      71k           
>   
> cache-auto-1-thread     seqread-libaio          260(MiB/s)      65k           
>   
> 
> cache-auto              seqread-libaio-multi    1508(MiB/s)     377k          
>   
> cache-auto-1-thread     seqread-libaio-multi    986(MiB/s)      246k          
>   
> 
> cache-auto              randread-psync          35(MiB/s)       9191          
>   
> cache-auto-1-thread     randread-psync          55(MiB/s)       13k           
>   
> 
> cache-auto              randread-psync-multi    179(MiB/s)      44k           
>   
> cache-auto-1-thread     randread-psync-multi    209(MiB/s)      52k           
>   
> 
> cache-auto              randread-mmap           32(MiB/s)       8273          
>   
> cache-auto-1-thread     randread-mmap           50(MiB/s)       12k           
>   
> 
> cache-auto              randread-mmap-multi     161(MiB/s)      40k           
>   
> cache-auto-1-thread     randread-mmap-multi     185(MiB/s)      46k           
>   
> 
> cache-auto              randread-libaio         268(MiB/s)      67k           
>   
> cache-auto-1-thread     randread-libaio         254(MiB/s)      63k           
>   
> 
> cache-auto              randread-libaio-multi   256(MiB/s)      64k           
>   
> cache-auto-1-thread     randread-libaio-multi   155(MiB/s)      38k           
>   
> 
> cache-auto              seqwrite-psync          23(MiB/s)       6026          
>   
> cache-auto-1-thread     seqwrite-psync          30(MiB/s)       7925          
>   
> 
> cache-auto              seqwrite-psync-multi    100(MiB/s)      25k           
>   
> cache-auto-1-thread     seqwrite-psync-multi    154(MiB/s)      38k           
>   
> 
> cache-auto              seqwrite-mmap           343(MiB/s)      85k           
>   
> cache-auto-1-thread     seqwrite-mmap           355(MiB/s)      88k           
>   
> 
> cache-auto              seqwrite-mmap-multi     408(MiB/s)      102k          
>   
> cache-auto-1-thread     seqwrite-mmap-multi     438(MiB/s)      109k          
>   
> 
> cache-auto              seqwrite-libaio         41(MiB/s)       10k           
>   
> cache-auto-1-thread     seqwrite-libaio         65(MiB/s)       16k           
>   
> 
> cache-auto              seqwrite-libaio-multi   137(MiB/s)      34k           
>   
> cache-auto-1-thread     seqwrite-libaio-multi   214(MiB/s)      53k           
>   
> 
> cache-auto              randwrite-psync         22(MiB/s)       5801          
>   
> cache-auto-1-thread     randwrite-psync         30(MiB/s)       7927          
>   
> 
> cache-auto              randwrite-psync-multi   100(MiB/s)      25k           
>   
> cache-auto-1-thread     randwrite-psync-multi   151(MiB/s)      37k           
>   
> 
> cache-auto              randwrite-mmap          31(MiB/s)       7984          
>   
> cache-auto-1-thread     randwrite-mmap          55(MiB/s)       13k           
>   
> 
> cache-auto              randwrite-mmap-multi    124(MiB/s)      31k           
>   
> cache-auto-1-thread     randwrite-mmap-multi    213(MiB/s)      53k           
>   
> 
> cache-auto              randwrite-libaio        40(MiB/s)       10k           
>   
> cache-auto-1-thread     randwrite-libaio        64(MiB/s)       16k           
>   
> 
> cache-auto              randwrite-libaio-multi  139(MiB/s)      34k           
>   
> cache-auto-1-thread     randwrite-libaio-multi  212(MiB/s)      53k           
>   
> 
> 
> 
> 
> 
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