Re: [RFC PATCH 00/20] Introduce the famfs shared-memory file system

[John Groves]

On 24/02/26 07:53AM, Luis Chamberlain wrote:
> On Mon, Feb 26, 2024 at 07:27:18AM -0600, John Groves wrote:
> > Run status group 0 (all jobs):
> >   WRITE: bw=29.6GiB/s (31.8GB/s), 29.6GiB/s-29.6GiB/s (31.8GB/s-31.8GB/s), io=44.7GiB (48.0GB), run=1511-1511msec
> 
> > This is run on an xfs file system on a SATA ssd.
> 
> To compare more closer apples to apples, wouldn't it make more sense
> to try this with XFS on pmem (with fio -direct=1)?
> 
>   Luis

Makes sense. Here is the same command line I used with xfs before, but 
now it's on /dev/pmem0 (the same 128G, but converted from devdax to pmem
because xfs requires that.

fio -name=ten-256m-per-thread --nrfiles=10 -bs=2M --group_reporting=1 --alloc-size=1048576 --filesize=256MiB --readwrite=write --fallocate=none --numjobs=48 --create_on_open=0 --ioengine=io_uring --direct=1 --directory=/mnt/xfs
ten-256m-per-thread: (g=0): rw=write, bs=(R) 2048KiB-2048KiB, (W) 2048KiB-2048KiB, (T) 2048KiB-2048KiB, ioengine=io_uring, iodepth=1
..
fio-3.33
Starting 48 processes
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
ten-256m-per-thread: Laying out IO files (10 files / total 2441MiB)
Jobs: 36 (f=360): [W(3),_(1),W(3),_(1),W(1),_(1),W(6),_(1),W(1),_(1),W(1),_(1),W(7),_(1),W(3),_(1),W(2),_(2),W(4),_(1),W(5),_(1)][77.8%][w=15.1GiB/s][w=7750 IOPS][eta 00m:02s]
ten-256m-per-thread: (groupid=0, jobs=48): err= 0: pid=8798: Mon Feb 26 15:10:30 2024
  write: IOPS=7582, BW=14.8GiB/s (15.9GB/s)(114GiB/7723msec); 0 zone resets
    slat (usec): min=23, max=7352, avg=131.80, stdev=151.63
    clat (usec): min=385, max=22638, avg=5789.74, stdev=3124.93
     lat (usec): min=432, max=22724, avg=5921.54, stdev=3133.18
    clat percentiles (usec):
     |  1.00th=[  799],  5.00th=[ 1467], 10.00th=[ 2073], 20.00th=[ 3097],
     | 30.00th=[ 3949], 40.00th=[ 4752], 50.00th=[ 5473], 60.00th=[ 6194],
     | 70.00th=[ 7046], 80.00th=[ 8029], 90.00th=[ 9634], 95.00th=[11338],
     | 99.00th=[16319], 99.50th=[17957], 99.90th=[20055], 99.95th=[20579],
     | 99.99th=[21365]
   bw (  MiB/s): min=10852, max=26980, per=100.00%, avg=15940.43, stdev=88.61, samples=665
   iops        : min= 5419, max=13477, avg=7963.08, stdev=44.28, samples=665
  lat (usec)   : 500=0.15%, 750=0.47%, 1000=1.34%
  lat (msec)   : 2=7.40%, 4=21.46%, 10=60.57%, 20=8.50%, 50=0.11%
  cpu          : usr=2.33%, sys=0.32%, ctx=58806, majf=0, minf=36301
  IO depths    : 1=100.0%, 2=0.0%, 4=0.0%, 8=0.0%, 16=0.0%, 32=0.0%, >=64=0.0%
     submit    : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
     complete  : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
     issued rwts: total=0,58560,0,0 short=0,0,0,0 dropped=0,0,0,0
     latency   : target=0, window=0, percentile=100.00%, depth=1

Run status group 0 (all jobs):
  WRITE: bw=14.8GiB/s (15.9GB/s), 14.8GiB/s-14.8GiB/s (15.9GB/s-15.9GB/s), io=114GiB (123GB), run=7723-7723msec

Disk stats (read/write):
  pmem0: ios=0/0, merge=0/0, ticks=0/0, in_queue=0, util=0.00%


I only have some educated guesses as to why famfs is faster. Since files 
are preallocated, they're always contiguous. And famfs is vastly simpler
because it isn't aimed at general purpose uses cases (and indeed can't
handle them).

Regards,
John