Filesystem operations slower in 13.0 than 12.2

[Mark Millard]

Christos Chatzaras chris at cretaforce.gr wrote on
Thu Mar 4 21:41:01 UTC 2021 :


> After finding slow filesystem operations with 13.0-BETA2 I did more tests.
> 
> All tests done with same hardware (Seagate ST4000NM0245 4TB HDD - 2 disks with RAID-1 using gmirror).
> 
> Filesystem mounted with noatime.
> 
> Command used:
> 
> /usr/bin/time -l portsnap extract
> 
> but similar differences I see with "/usr/bin/time -l rm -fr /usr/ports"

I doubt that "rm -fr" gets large differences of the
type:

(from 12.2p4:)
         0  messages sent
         0  messages received
vs. (13.0-BETA4 and 14.0-CURRENT:)
      4412  messages sent
   2536379  messages received

In other words, large variations in Inter-Process-Communiciation
counts, especially "received".

It is not obvious that the "portsnap extract" issue
is dominated by file system I/O vs IPC issues.

portsanp is a script and does something that looks
like the following, with the "while read" happening
over 29000 times:

. . . | while read FILE HASH; do
                echo ${PORTSDIR}/${FILE}
                if ! [ -s "${WORKDIR}/files/${HASH}.gz" ]; then
                        echo "files/${HASH}.gz not found -- snapshot corrupt."
                        return 1
                fi
                case ${FILE} in
                */)
                        rm -rf ${PORTSDIR}/${FILE%/}
                        mkdir -p ${PORTSDIR}/${FILE}
                        tar -xz --numeric-owner -f ${WORKDIR}/files/${HASH}.gz \
                            -C ${PORTSDIR}/${FILE}
                        ;;
                *)
                        rm -f ${PORTSDIR}/${FILE}
                        tar -xz --numeric-owner -f ${WORKDIR}/files/${HASH}.gz \
                            -C ${PORTSDIR} ${FILE}
                        ;;
                esac
        done; then

I expect that the "tar -xz . . . *.gz" sort of commands
also involve internal IPC use. (It looked like the
portsnap script has not changed noticeably since
something like late 2016.)

(13.0-BETA2 showed a large "voluntary context switches"
difference as well, but I ignore that middle step in
the version sequence here.)

So I expect publishing the "rm -fr /usr/ports" figures
from "time -l" would be appropriate. I do not know if
the reports should be via separate topic or not but I
doubt the figures with large differences will be the
same for most-modern vs. older: I do not expect notable
IPC from "rm -fr".

> ----------
> 
> FreeBSD 12.2p4 
> 
>        98.18 real        35.31 user        59.31 sys
>      49064  maximum resident set size
>         21  average shared memory size
>          3  average unshared data size
>         86  average unshared stack size
>   11821398  page reclaims
>          0  page faults
>          0  swaps
>         29  block input operations
>       2783  block output operations
>          0  messages sent
>          0  messages received
>          0  signals received
>     354648  voluntary context switches
>        322  involuntary context switches
> 
> ----------
> 
> FreeBSD 13.0-BETA2 (2021-02-12)
> 
>       497.88 real        76.06 user       120.03 sys
>      49032  maximum resident set size
>         22  average shared memory size
>          3  average unshared data size
>         91  average unshared stack size
>   12288156  page reclaims
>         23  page faults
>          0  swaps
>      29890  block input operations
>     621229  block output operations
>       4412  messages sent
>    2536379  messages received
>          0  signals received
>    1004790  voluntary context switches
>        251  involuntary context switches
> 
> --------------
> 
> FreeBSD 13.0-BETA4 (2021-02-26)
> 
>       163.81 real        71.93 user       107.32 sys
>      49032  maximum resident set size
>         21  average shared memory size
>          3  average unshared data size
>         89  average unshared stack size
>   12288156  page reclaims
>          5  page faults
>          0  swaps
>        716  block input operations
>        868  block output operations
>       4412  messages sent
>    2536379  messages received
>          0  signals received
>     355244  voluntary context switches
>        277  involuntary context switches
> 
> ----------
> 
> FreeBSD 14-CURRENT (2021-03-04)
> 
>       255.43 real        74.94 user       148.90 sys
>      49032  maximum resident set size
>         23  average shared memory size
>          3  average unshared data size
>         96  average unshared stack size
>   12288156  page reclaims
>         23  page faults
>          0  swaps
>      31207  block input operations
>        175  block output operations
>       4412  messages sent
>    2536379  messages received
>          0  signals received
>     385527  voluntary context switches
>        369  involuntary context switches
> 
> ----------
> 
> Differences between 13.0 and 14-CURRENT maybe related to debugging features.
> 
> But 13.0-BETA4 is slower than 12.2. Does someone have more information about this?

Again, I expect that the "time -l" figures may point in
different directions for "portsnap extract" vs.
"rm -fr /usr/ports" in your context. The question may
need to be split because the answers may be different.

===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)