On Thu, 2011-03-17 at 08:30 +1100, NeilBrown wrote: > On Wed, 16 Mar 2011 10:20:03 -0400 Trond Myklebust > <Trond.Myklebust@xxxxxxxxxx> wrote: > > > On Wed, 2011-03-16 at 10:14 -0400, Bryan Schumaker wrote: > > > I guess I misunderstood what to publish test results for? I know I included numbers on one of the patches (commit 82f2e5472e2304e531c2fa85e457f4a71070044e, copied below)... I'll find the numbers you're asking about and post them. > > > > > > -Bryan > > > > > > commit 82f2e5472e2304e531c2fa85e457f4a71070044e > > > Author: Bryan Schumaker <bjschuma@xxxxxxxxxx> > > > Date: Thu Oct 21 16:33:18 2010 -0400 > > > > > > NFS: Readdir plus in v4 > > > > > > By requsting more attributes during a readdir, we can mimic the readdir plus > > > operation that was in NFSv3. > > > > > > To test, I ran the command `ls -lU --color=none` on directories with various > > > numbers of files. Without readdir plus, I see this: > > > > > > n files | 100 | 1,000 | 10,000 | 100,000 | 1,000,000 > > > --------+-----------+-----------+-----------+-----------+---------- > > > real | 0m00.153s | 0m00.589s | 0m05.601s | 0m56.691s | 9m59.128s > > > user | 0m00.007s | 0m00.007s | 0m00.077s | 0m00.703s | 0m06.800s > > > sys | 0m00.010s | 0m00.070s | 0m00.633s | 0m06.423s | 1m10.005s > > > access | 3 | 1 | 1 | 4 | 31 > > > getattr | 2 | 1 | 1 | 1 | 1 > > > lookup | 104 | 1,003 | 10,003 | 100,003 | 1,000,003 > > > readdir | 2 | 16 | 158 | 1,575 | 15,749 > > > total | 111 | 1,021 | 10,163 | 101,583 | 1,015,784 > > > > > > With readdir plus enabled, I see this: > > > > > > n files | 100 | 1,000 | 10,000 | 100,000 | 1,000,000 > > > --------+-----------+-----------+-----------+-----------+---------- > > > real | 0m00.115s | 0m00.206s | 0m01.079s | 0m12.521s | 2m07.528s > > > user | 0m00.003s | 0m00.003s | 0m00.040s | 0m00.290s | 0m03.296s > > > sys | 0m00.007s | 0m00.020s | 0m00.120s | 0m01.357s | 0m17.556s > > > access | 3 | 1 | 1 | 1 | 7 > > > getattr | 2 | 1 | 1 | 1 | 1 > > > lookup | 4 | 3 | 3 | 3 | 3 > > > readdir | 6 | 62 | 630 | 6,300 | 62,993 > > > total | 15 | 67 | 635 | 6,305 | 63,004 > > > > > > Readdir plus disabled has about a 16x increase in the number of rpc calls an > > > is 4 - 5 times slower on large directories. > > > > Right. Those are the numbers that convinced me... > > > > > > Lies, Damn Lies, and ...... > > > while these are impressive numbers they only tell half the story. > > If a change makes one common operation 4 times faster, and another common > operation 10 times slower, it is a good change? or even an acceptable change? > > (The "10 times" is not a definite statistic - it is a guess based on > a low-detail report) > > So it is obvious that there is sometimes value in using readdirplus, > it is equally obvious that there is sometimes a cost. > > Switching the default from "not paying the cost when it is big" to > "always paying the cost" is wrong. That's what the nordirplus mount flag is for. Keeping an arbitrary limit in the face of evidence that it is hurting is equally wrong. -- Trond Myklebust Linux NFS client maintainer NetApp Trond.Myklebust@xxxxxxxxxx www.netapp.com -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
