On Tue, May 23, 2023 at 7:18 AM Chris Chilvers [off-list ref] wrote:

On Fri, 19 May 2023 at 10:40, David Howells [off-list ref] wrote:

quoted

Chris Chilvers [off-list ref] wrote:

quoted

While testing the fscache performance fixes [1] that were merged into 6.4-rc1
it appears that the caching no longer works. The client will write to the cache
but never reads.

Can you try reading from afs?  You would need to enable CONFIG_AFS_FS in your
kernel if it's not already set.

Install kafs-client and do:

        systemctl enable afs.mount
        md5sum /afs/openafs.org/software/openafs/1.9.1/openafs-1.9.1-doc.tar.bz2
        cat /proc/fs/fscache/stats

FS-Cache statistics
Cookies: n=13 v=7 vcol=0 voom=0
Acquire: n=13 ok=13 oom=0
LRU    : n=1 exp=0 rmv=0 drp=0 at=2833
Invals : n=0
Updates: n=0 rsz=0 rsn=0
Relinqs: n=0 rtr=0 drop=0
NoSpace: nwr=0 ncr=0 cull=0
IO     : rd=0 wr=18
RdHelp : RA=18 RP=0 WB=0 WBZ=0 rr=0 sr=0
RdHelp : ZR=1 sh=0 sk=0
RdHelp : DL=18 ds=18 df=0 di=0
RdHelp : RD=0 rs=0 rf=0
RdHelp : WR=18 ws=18 wf=0

This was on an instance that was only just created, so the cache was
initially unused (all the counters were 0).

quoted

        umount /afs/openafs.org
        md5sum /afs/openafs.org/software/openafs/1.9.1/openafs-1.9.1-doc.tar.bz2
        cat /proc/fs/fscache/stats

FS-Cache statistics
Cookies: n=13 v=7 vcol=0 voom=0
Acquire: n=26 ok=26 oom=0
LRU    : n=1 exp=1 rmv=0 drp=0 at=467
Invals : n=0
Updates: n=0 rsz=0 rsn=0
Relinqs: n=13 rtr=0 drop=13
NoSpace: nwr=0 ncr=0 cull=0
IO     : rd=18 wr=18
RdHelp : RA=36 RP=0 WB=0 WBZ=0 rr=0 sr=0
RdHelp : ZR=1 sh=0 sk=0
RdHelp : DL=18 ds=18 df=0 di=0
RdHelp : RD=18 rs=18 rf=0
RdHelp : WR=18 ws=18 wf=0

Looks like the cache is working fine with AFS. The second md5sum
seemed a lot quicker than the first.

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I don't think this test demonstrates the failure Chris is seeing, or
correct me if I'm wrong Chris.

Chris, does this same test fail for you with NFS on 6.4-rc1?  The same
test passes for me with NFSv3.
1st time through: writes to the cache seen, no reads: IO     : rd=0 wr=16
2nd time through: reads from the cache seen, no writes: IO     : rd=16 wr=16


# mount -o vers=3,fsc 127.0.0.1:/export/ /mnt/nfs
# cat /proc/fs/fscache/stats
FS-Cache statistics
Cookies: n=0 v=1 vcol=0 voom=0
Acquire: n=0 ok=0 oom=0
LRU    : n=0 exp=0 rmv=0 drp=0 at=0
Invals : n=0
Updates: n=0 rsz=0 rsn=0
Relinqs: n=0 rtr=0 drop=0
NoSpace: nwr=0 ncr=0 cull=0
IO     : rd=0 wr=0
RdHelp : RA=0 RP=0 WB=0 WBZ=0 rr=0 sr=0
RdHelp : ZR=0 sh=0 sk=0
RdHelp : DL=0 ds=0 df=0 di=0
RdHelp : RD=0 rs=0 rf=0
RdHelp : WR=0 ws=0 wf=0
# md5sum /mnt/nfs/openafs-1.9.1-doc.tar.bz2
ca25530ec01afc3b71bc081bc93b87cf  /mnt/nfs/openafs-1.9.1-doc.tar.bz2
# cat /proc/fs/fscache/stats
FS-Cache statistics
Cookies: n=1 v=1 vcol=0 voom=0
Acquire: n=1 ok=1 oom=0
LRU    : n=1 exp=0 rmv=0 drp=0 at=6444
Invals : n=0
Updates: n=1 rsz=0 rsn=0
Relinqs: n=0 rtr=0 drop=0
NoSpace: nwr=0 ncr=0 cull=0
IO     : rd=0 wr=16
RdHelp : RA=16 RP=0 WB=0 WBZ=0 rr=0 sr=0
RdHelp : ZR=1 sh=0 sk=0
RdHelp : DL=16 ds=16 df=0 di=0
RdHelp : RD=0 rs=0 rf=0
RdHelp : WR=16 ws=16 wf=0
# umount /mnt/nfs
# mount -o vers=3,fsc 127.0.0.1:/export/ /mnt/nfs
# md5sum /mnt/nfs/openafs-1.9.1-doc.tar.bz2
ca25530ec01afc3b71bc081bc93b87cf  /mnt/nfs/openafs-1.9.1-doc.tar.bz2
# cat /proc/fs/fscache/stats
FS-Cache statistics
Cookies: n=1 v=1 vcol=0 voom=0
Acquire: n=2 ok=2 oom=0
LRU    : n=1 exp=1 rmv=0 drp=0 at=6710
Invals : n=0
Updates: n=2 rsz=0 rsn=0
Relinqs: n=1 rtr=0 drop=1
NoSpace: nwr=0 ncr=0 cull=0
IO     : rd=16 wr=16
RdHelp : RA=32 RP=0 WB=0 WBZ=0 rr=0 sr=0
RdHelp : ZR=1 sh=0 sk=0
RdHelp : DL=16 ds=16 df=0 di=0
RdHelp : RD=16 rs=16 rf=0
RdHelp : WR=16 ws=16 wf=0
# uname -r
6.4.0-rc1